U.S. patent application number 09/932175 was filed with the patent office on 2001-12-27 for methods for responsively treating neurological disorders.
Invention is credited to Fischell, David R., Fischell, Robert E., Upton, Adrian R.M..
Application Number | 20010056290 09/932175 |
Document ID | / |
Family ID | 27035975 |
Filed Date | 2001-12-27 |
United States Patent
Application |
20010056290 |
Kind Code |
A1 |
Fischell, Robert E. ; et
al. |
December 27, 2001 |
Methods for responsively treating neurological disorders
Abstract
Disclosed is a multiple electrode, closed-loop, responsive
system for the treatment of certain neurological diseases such as
epilepsy, migraine headaches and Parkinson's disease. Brain
electrodes would be placed in close proximity to the brain or deep
within brain tissue. When a neurological event such as the onset of
an epileptic seizure occurs, EEG signals from the electrodes are
processed by signal conditioning means in a control module that can
be placed beneath the patient's scalp, within the patient's chest,
or situated externally on the patient. Neurological event detection
means in the control module will then cause a response to be
generated for stopping the neurological event. The response could
be an electrical signal to brain electrodes or to electrodes
located remotely in the patient's body. The response could also be
the release of medication or the application of a sensory input
such as sound, light or mechanical vibration or electrical
stimulation of the skin. The response to the neurological event can
originate from devices either internal or external to the patient.
The system also has the capability for multi-channel recording of
EEG related signals that occur both before and after the detection
of a neurological event. Programmability of many different
operating parameters of the system by means of external equipment
provides adaptability for treating patients who manifest different
symptoms and who respond differently to the response generated by
the system.
Inventors: |
Fischell, Robert E.;
(Dayton, MD) ; Fischell, David R.; (Fair Haven,
NJ) ; Upton, Adrian R.M.; (Dundas, CA) |
Correspondence
Address: |
NEUROPACE, INC.
255 SANTA ANA COURT
SUNNYVALE
CA
94085
US
|
Family ID: |
27035975 |
Appl. No.: |
09/932175 |
Filed: |
August 17, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09932175 |
Aug 17, 2001 |
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09628977 |
Aug 2, 2000 |
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09628977 |
Aug 2, 2000 |
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09450303 |
Nov 29, 1999 |
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6128538 |
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09450303 |
Nov 29, 1999 |
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08957869 |
Oct 27, 1997 |
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6016449 |
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Current U.S.
Class: |
607/45 |
Current CPC
Class: |
A61N 1/36075 20130101;
A61N 1/36025 20130101; A61N 1/36067 20130101; A61N 1/36017
20130101; A61N 1/37252 20130101; A61N 1/36064 20130101; A61N
1/36135 20130101 |
Class at
Publication: |
607/45 |
International
Class: |
A61N 001/36 |
Claims
What is claimed is:
1. A method for providing responsive therapy to a patient with
epilepsy, comprising the steps of: receiving an EEG signal with an
implanted control module; detecting a neurological event in the EEG
signal; and performing an action in response to the detected
neurological event; wherein the action provides a therapeutic
effect to the patient.
2. The method for providing responsive therapy of claim 1, further
comprising the step of processing the EEG signal with an electronic
circuit in the implanted control module.
3. The method for providing responsive therapy of claim 2, wherein
the electronic circuit comprises an event detection subsystem.
4. The method for providing responsive therapy of claim 1, further
comprising the step of converting the EEG signal into a digital
data stream.
5. The method for providing responsive therapy of claim 4, wherein
the digital data stream is representative of the EEG signal.
6. The method for providing responsive therapy of claim 4, wherein
the digital data stream is representative of an energy spectrum of
the EEG signal.
7. The method for providing responsive therapy of claim 4, further
comprising the step of processing the digital data stream.
8. The method for providing responsive therapy of claim 7, wherein
the step of processing the digital data stream employs a digital
signal processor.
9. The method for providing responsive therapy of claim 4, wherein
the step of detecting a neurological event comprises performing a
detection algorithm on the digital data stream.
10. The method for providing responsive therapy of claim 9, wherein
the step of performing the detection algorithm comprises the steps
of: extracting a characteristic from the digital data stream;
comparing the characteristic of the digital data stream to a
threshold; and if the characteristic exceeds the threshold,
indicating that a neurological event has been detected.
11. The method for providing responsive therapy of claim 10,
wherein the characteristic comprises an energy of the EEG signal in
a frequency band.
12. The method for providing responsive therapy of claim 10,
wherein the characteristic comprises a signal amplitude.
13. The method for providing responsive therapy of claim 10,
wherein the characteristic comprises a signal event density within
a time period.
14. The method for providing responsive therapy of claim 1, wherein
the step of performing an action comprises delivering an electrical
stimulation signal to a brain of the patient.
15. The method for providing responsive therapy of claim 14,
wherein the step of delivering an electrical stimulation signal
comprises the steps of: generating the electrical stimulation
signal; and transmitting the electrical stimulation signal to a
stimulation electrode via a lead.
16. The method for providing responsive therapy of claim 15,
wherein the stimulation electrode is implanted in the brain of the
patient.
17. The method for providing responsive therapy of claim 14,
wherein the electrical stimulation signal includes a pulse.
18. The method for providing responsive therapy of claim 17,
wherein the pulse is biphasic.
19. The method for providing responsive therapy of claim 1, wherein
the step of performing an action comprises actuating a buzzer to
cause an acoustic signal to be perceived by the patient.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present invention is a continuation of co-pending U.S.
patent application Ser. No. 09/628,977, filed Aug. 2, 2000, which
is a continuation of U.S. patent application Ser. No. 09/450,303,
filed Nov. 29, 1999, now U.S. Pat. No. 6,128,538, which is in turn
a continuation of U.S. patent application Ser. No. 08/957,869,
filed Oct. 27, 1997, now U.S. Pat. No. 6,016,449.
FIELD OF THE INVENTION
[0002] This invention is in the field of devices for the treatment
of neurological disorders in human subjects, particularly those
disorders that originate in the brain.
BACKGROUND OF THE INVENTION
[0003] The current state of the art in treating neurological
disorders such as epilepsy or Parkinson's disease involves either
drugs or the open-loop electrical stimulation of neurologic tissue.
Drug therapy has been shown to have significant short and long term
side effects and is often ineffective. In U.S. Pat. No. 3,850,161,
Liss describes a continuous closed-loop feedback system which will
always feedback part of the brain EEG signal to separate electrodes
so that if a large EEG signal occurs it will be fed back in an
attempt to cancel out the original signal. This system does not
take advantage of recently developed digital signal processing and
microcomputer technology by which feedback signals can be activated
only when a neurological event occurs, nor does it provide a
practical means to recognize and intervene during early stages in
the evolution of a neurological event. In addition, the Liss device
is not programmable and it does not provide a means to record EEG
signals. Examples of a "neurological event" are the occurrence of
an epileptic seizure or the occurrence of a migraine headache. A
"neurological event" is defined herein as either the precursor of
an event such as an epileptic seizure, or the epileptic seizure
itself.
[0004] Maurer and Sorenson in U.S. Pat. No. 4,019,518 describe a
combined internal/external system for electrical stimulation of the
body with biphasic pulses but do not describe any means of
detecting neurological events. Fischell in U.S. Pat. No. 4,373,527
describes a programmable medication infusion system but does not
anticipate its use in response to a detected neurological
event.
[0005] More recently, a device has been approved for human use to
stimulate the vagus nerve in a continuous fashion with the
objective of decreasing the rate of epileptic seizures. Clinical
reports on such devices indicate only a modest degree of success in
that only 50% of the patients experience a greater than 20%
reduction in the rate of epileptic seizures. Another device that
has been recently introduced into clinical practice utilizes
continuous stimulation of the thalamus for the treatment of
involuntary motion disorders such as Parkinson's syndrome.
[0006] Neither of these two open-loop devices described above is
highly effective for the treatment of a neurological disorder such
as epilepsy, and neither anticipates the use of decision making in
order to optimize a response to turn off the neurological event nor
the recording of EEG signals.
[0007] The automatic implantable cardiac defibrillator is an
example of a decision making device having data recording
capability that has been successfully used in a decision based
closed-loop mode for the treatment of ventricular fibrillation.
However, the requirements for detection and treatment of
ventricular fibrillation are significantly simpler and certainly
different from the requirements for a device to detect and treat an
impending epileptic seizure. Specifically, an implantable cardiac
defibrillator requires only a single signal, namely the heart's
ECG, in order to detect a fibrillation event. What is more, only a
single pair of electrodes is required for detection of the
fibrillation event and that same pair of electrodes can be used to
provide an electrical stimulus for electrical defibrillation. A
heart defibrillator electrode is adapted to be placed on or in
close proximity to the heart and is not suitable for use as a brain
electrode.
[0008] Coker and Fischell in U.S. Pat. No. 4,581,758 describe
sophisticated signal processing techniques using the sum of squared
signals from two microphones to identify the direction with respect
to a person from whom human speech originates. Although the Coker
and Fischell patent teaches several signal processing techniques
which may be applied with others to detect neurological events, the
Coker and Fischell method is aimed at identifying the location of
the speech source, while one of the goals of the present invention
is to utilize the known location of the source of EEG signals to
help identify an abnormal EEG which signifies an impending
neurological event.
[0009] The NeuroCybernetic Prosthesis System recently made
available for the treatment of epileptic seizures, utilizes
continuous open-loop stimulation of the vegas nerve. This device
does not sense the onset of an epileptic seizure, and it utilizes
wires that are placed in the neck. Because of the frequent motions
of such wires, they will have a tendency to fracture. No existing
system utilizes electrodes, electrical wires and a control module
that are entirely contained within the patient's scalp and
essentially all contained within the patient's cranium. Such
systems would not have any repeated bending of connecting wires
thereby improving long term reliability. Furthermore, the
NeuroCybernetic Prosthesis System does not use a rechargeable
battery, nor does it utilize a separate external device controlled
by the patient to activate the implanted system at the start of a
neurological event in order to decrease the severity or time
duration of the neurological event.
SUMMARY OF THE INVENTION
[0010] The present invention is a multiple electrode, closed-loop
system for the treatment of certain neurological disorders such as
epilepsy, migraine headaches and Parkinson's disease. A purpose of
the present invention is to overcome the shortcomings of all prior
art devices for the treatment of such disorders. Specifically, the
present invention combines a multi-electrode array with
sophisticated signal processing techniques to achieve reliable
detection of the onset of a neurological event (such as an
epileptic seizure or migraine headache) typically originating from
a focus of limited spatial extent within the brain. It is well
known that in certain patients, epileptic seizures consistently
originate from a single location within the brain. However, the
system described herein is also adaptable for the treatment of a
neurological event that involves a major portion or possibly all of
the brain tissue.
[0011] The present invention also provides means for generating an
ensemble of coordinated electrical stimuli designed to terminate
the neurological event immediately upon (or even prior to) its
onset. Thus, the present invention is a responsive detection and
stimulation system for the early recognition and prompt treatment
of a neurological event.
[0012] The present invention envisions a multiplicity of brain
electrodes placed either within the brain, on the surface of the
brain itself, or on the dura mater that surrounds the brain. Some
one, several, or all of these brain electrodes can be used for
detection of an abnormal neurological event such as an epileptic
seizure. A responsive stimulation signal can also be applied to any
one, several, or all elements of such an electrode array. The
responsive stimulation signals sent to each electrode may be
identical or they may be programmed to differ in amplitude,
frequency, waveform, phase and time duration. It is also envisioned
that sensing electrodes may be entirely separate from the
electrodes used for responsive stimulation.
[0013] The present invention envisions that a neurological event
can be reliably detected in the presence of a normal EEG signal and
in the presence of external noise by the use of modern and
sophisticated signal processing techniques. Specifically, the
electrical signal from an epileptic focus within a specific and
limited spatial region within the brain can be reliably detected by
combining the signals received at different electrodes that are
placed at different distances from the epileptic focus. To improve
signal-to-noise ratio, the signal received at a specified location
which is at a specific distance from the epileptic focus could have
a specific time delay to account for the propagation time it takes
for the signal to reach that electrode. For example, if a first
electrode is located directly over the site of the epileptic focus
and a second electrode is located at a distance of several
centimeters from the focus, then to combine these two signals
together to optimize detection of a neurological event, the signal
at the first (closest) electrode must have an added time delay to
account for the time required for the signal to arrive at the
position of the second electrode. Thus cross-correlation of EEG
signals in the time domain is envisioned to be within the scope of
the present invention.
[0014] It is also envisioned that appropriate selection (i.e.,
location) of electrode sites can be used to enhance the reliability
for detection and termination of a neurological event. Thus, the
present invention envisions enhancement of detection by the use of
the spatial domain as it applies to the positioning of detection
and treatment electrodes.
[0015] Finally, the present invention also envisions
signal-to-noise enhancement for optimizing the detection of
neurological events by searching for signals in a particular
frequency domain. For example, a low-pass filter that excludes
signals above 5 Hz could be used to enhance the reliability for
detection of a neurological event for certain patients. In
addition, detection may be enhanced by first conditioning the EEG
signals using programmable, multiple step, signal processing. The
processing steps that are envisioned for this signal conditioning
include signal summing, squaring, subtracting, amplifying, and
filtering.
[0016] It is also envisioned that any combination of techniques for
signal detection in the time, spatial or frequency domain could be
used for providing a highly reliable system for the detection of a
neurological event.
[0017] The present invention envisions four different modalities
for stopping the progression of a neurological event such as an
epileptic seizure once it has been detected. A preferred method is
to provide a responsive stimulation electrical signal, a second
method is to release medication in response to the detection of an
event, a third method is to provide an electrical short circuit in
the vicinity of the epileptic focus to prevent the occurrence of a
full epileptic seizure and a fourth method is the application of a
sensory input through normal sensory pathways. Such sensory input
could be acoustic (sound input), visual (light input), or other
sensory input such as mechanical vibration or electrical
stimulation of the skin. Of course it is envisioned that any two or
more of these modalities can be used in combination in order to
preclude, prevent or decrease the severity of a neurological event
such as an epileptic seizure, migraine headache, Parkinson's
disease tremor, etc.
[0018] A valuable attribute of the present invention is the ability
to record the EEG signal from any one or all of the detection
electrodes. Typically the EEG signal would be continuously recorded
in a first-in first-out (FIFO) digital data recording system where
the current data over-writes the oldest data as memory storage
capacity is exceeded. In the event that a neurological event was
detected, the device would save the preceding several minutes of
data while continuing to record subsequent EEG data after the
application of a response such as responsive stimulation, short
circuiting of some electrode(s) or the delivery of a bolus of
medication. It is conceived that the device would hold in memory
the recording made for several minutes both before and after the
neurological event. These data would then be read out by the
patient's physician on a regular basis; e.g., every three months or
more frequently if the device did not promptly terminate some
neurological event. It is also anticipated that the patient could
use a patient's initiating device to trigger the retention of
several minutes of data recording of the EEG signal from a
pre-selected group of electrodes.
[0019] It is also conceived that certain other data be recorded
that can be helpful to the physician for treating the patient.
These additional data would include: (1) the number of neurological
events detected since the last memory readout and; (2) the number
of responses triggered by the neurological events that were
delivered to the patient. Furthermore, the system can be programmed
so that when a neurological event is detected, the electrical
signal from any one or more of the multiple steps in the signal
conditioning can be stored in a digital memory. Additionally,
telemetry would be provided to the physician that would indicate
the serial number of the device that is implanted in the patient
and the date and time that each neurological event or patient
initiated recording occurred.
[0020] Another valuable attribute of the present invention is the
capability to program the functions and parameters of the system to
enhance the detection of a neurological event and to optimize the
system responses for stopping a neurological event such as an
epileptic seizure. Examples of programmable functions and
parameters are: (1) the time delay introduced for a signal being
received from a specific electrode; (2) the use or non-use of a
specific electrode; (3) the frequency response characteristic of
the channel assigned to process the signal received from a specific
electrode; (4) whether or not a particular electrode is
electrically shorted to another electrode or to the metal case of
the device after a neurological event has been detected; (5) the
amplitude, frequency, duration, phase and wave-form of the response
signal delivered to a specific electrode; (6) the allocation of
memory for storing EEG signals as received from one or more
electrodes; (7) determination as to whether or not the data from a
particular electrode will be stored in memory; (8) the amplitude,
frequency and time duration of an acoustic, visual, or other
sensory input applied to the patient in response to the detection
of a neurological event, and (9) the specification of statistical
data (histograms) to be recorded; for example, the number of
epileptic seizures and/or the number of responsive stimulations
delivered since the last memory readout by an attending physician.
These are some but not all of the programmable functions and
parameters that the system might utilize.
[0021] It should be understood that a telemetry signal would be
transmitted from the implanted device. External receiving equipment
typically located in the physician's office, would process that
signal and provide a paper print-out and a CRT display to indicate
the state to which all the parameters of the implanted device have
been programmed. For example, the display would indicate which
electrodes are active, what algorithm is being used for detection,
what specific bandwidth is being used with a specific electrode,
etc.
[0022] It should be understood that, unlike implantable automatic
heart defibrillators which generate a responsive signal only after
ventricular fibrillation has occurred, it is a goal of the present
invention to prevent full development of an epileptic seizure or
migraine headache before the actual occurrence of such an unwanted
neurological event. In this regard, the present invention is
entirely different from any implantable medical device (such as an
automatic heart defibrillator) that always allows the unwanted
event to occur.
[0023] A specific capability of this system is to provide
electrical stimulation to a specific portion of the brain as the
means of stopping a neurological event. It is believed that the
earliest possible detection of a seizure and treatment of aberrant
electrical activity from an epileptic focus has the highest
probability of aborting the occurrence of a full seizure. It is
envisioned that either through specific placement of treatment
electrodes or by adjusting the phase of signals applied to an array
of electrodes, stimulation can be directed to the location(s)
within the brain that offer the highest probability of stopping the
seizure.
[0024] It is believed that there is minimal or no effect if a
responsive stimulation is produced from an erroneously identified
event, i.e., a false positive. On the other hand, failure to
identify a real event is highly undesirable and could cause the
patient to undergo a severe seizure. Therefore, the design concept
of the current invention is to predispose the decision making
algorithm to never miss a real event while allowing a false
positive rate to be detected at up to 5 times the rate of actual
events.
[0025] Telemetry data transmitted from the implanted device can be
sent to a physician's workstation in the physician's office either
with the patient in the physician's office or remotely from the
patient's home by means of a modem. The physician's workstation can
also be used to specify all of the programmable parameters of the
implanted system.
[0026] A novel aspect of a preferred embodiment of this invention
is that the entire implantable portion of this system for treating
neurological disorders lies under the patient's scalp. Such
placement will either have the device located between the scalp and
the cranium or the within a hole in the cranium. Because of size
constraints, the intracranial location is the preferred
embodiment.
[0027] The implantable portion of the system includes; (1)
electrodes that lie in close proximity to or actually within the
brain; (2) a control module that contains a battery and all the
electronics for sensing, recording and controlling brain activity,
(3) electrically conducting wires that connect the control module
to the electrodes, (4) a buzzer providing an acoustic signal or
electrical "tickle" indicating that a neurological event has been
detected, and (5) an input-output wire coil (or antenna) used for
communication of the implanted system with any and all external
equipment. The battery that provides power for the system and an
electronics module are both contained within a metal shell that
lies under the patient's scalp. The metal shell which contains the
electronics module and the battery collectively form the control
module.
[0028] All electrodes connect by means of electrically conducting
wires to electrical terminals that are formed into the metal shell.
The electronics module is electrically joined to the brain
electrodes by means of the shell's electrical terminals which are
electrically joined to the wires that connect to the brain
electrodes.
[0029] An important aspect of the preferred embodiment of this
device is the fact that the shell containing the electronics module
and the battery, i.e. the control module, is to be placed in the
cranium of the skull at a place where a significant volume of bone
is removed. By placing the entire system within the cranium, (as
opposed to having some wires extending into or through the neck to
a control module in the chest) the probability of wire breakage due
to repeated wire bending is drastically reduced. However, the
present invention also envisions the placement in the chest or
abdomen of a control module if a large battery or a large volume
electronics module dictates such a large size for the control
module that it cannot be conveniently placed within the cranium.
Such a thoracic or abdominal placement of a control module would
require wires to be run through the neck.
[0030] The present invention also envisions the utilization of an
intracranial system for the treatment of certain diseases without
placing wires through the neck. Specifically, an alternative
embodiment of the invention envisions the use of electrodes in or
on the brain with an intracranial control module used in
conjunction with a remote sensor/actuator device. For example,
blood pressure could be sensed with a threshold of, let us say 150
mm Hg, and if that pressure was exceeded, a signal transmitted by
electrical conduction through the body from the remote
sensor/actuator device could be received at the control module and
that would cause brain stimulation in such a way as to reduce the
blood pressure. Conversely, if the brain detects pain and provides
a signal detectable by the intracranial system, a signal could be
sent by electrical conduction through the body to a remote
sensor/actuator device which could provide electrical stimulation
to locally stimulate a nerve to reduce the perception of that pain.
Still another example is that if the precursor of an epileptic
seizure is detected, a remote actuator could be used to
electrically stimulate one or both vagus nerves so as to stop the
epileptic seizure from occurring. Such a remote device could be
located in the trunk of the patient's body.
[0031] Another important aspect of this invention is that a
comparatively simple surgical procedure can be used to place the
control module just beneath the patient's scalp. A similar simple
procedure can be used to replace either the battery or both the
battery and the electronics module. Specifically, if the hair on
the scalp is shaved off at a site directly over where the control
module is implanted, an incision can then be made in the scalp
through which incision a depleted battery can be removed and
replaced with a new battery, or a more advanced electronics module
can replace a less capable or failed electronics module. The
incision can then be closed, and when the hair grows back, the
entire implanted system would be cosmetically undetectable. A good
cosmetic appearance is very important for the patient's
psychological well being.
[0032] The manner in which the control module, the electrodes and
the interconnecting wires are placed beneath the scalp is important
for the successful implantation of the entire implantable system.
Specifically, the control module is optimally placed in either the
left or right anterior quadrant of the cranium. Because the large
sagital sinus vein runs along the anterior-posterior center line of
the cranium, it is inadvisable to run epidural wires through that
region, and furthermore, it would be inadvisable to place the
control module directly over that major vein. Since movement of the
jaw causes motions of the scalp relative to the cranium, it is
advisable to run the connecting wires for electrodes that must be
placed on the anterior portion of the brain in the epidural space
as opposed to running them between the scalp and the cranium. Since
the middle meningeal artery and its branches run within grooves
interior to the posterior section of the cranium, it would be
inadvisable to connect to posterior placed electrodes by
utilization of connecting wires positioned in the epidural space
beneath the posterior portion of the cranium. Therefore, the
connecting wires for electrodes to be placed on a posterior portion
of the brain's surface are best located beneath the scalp, then
through burr holes in the cranium where they connect to any
electrodes placed in a posterior position on the surface of the
dura mater. Conversely, most of the length of the connecting wires
for electrodes located in the anterior portion of the brain would
be placed in the epidural space. In no case should epidural wires
be passed through the anterior-posterior centerline of the brain
where the large sagital sinus vein is located.
[0033] An important operational aspect of the implanted system is
the use of an input-output coil formed from many turns of fine wire
that is placed between the scalp and the cranium generally along
the anterior-posterior center line of the head. All communication
between the external equipment and the implanted system can be
accomplished by magnetic induction through the hair and scalp of
the patient. Examples of these signals are the readout of telemetry
from the implanted system, or the changing of some operational
parameter of the implanted system by means of a command from some
piece of external equipment. Furthermore, such an input-output coil
can be used to recharge a rechargeable battery that can be located
inside the control module. Since the input-output coil can be
placed on a posterior portion of the cranium, relative motion of
the scalp and cranium should not be a problem in that region.
[0034] By placing the input-output coil in an appropriate site just
beneath the scalp, the patient can be provided with a cap to be
worn on the head which cap includes a flexible coil that can
communicate by magnetic induction using an alternating magnetic
field with the implanted input-output coil. Such a cap could be
placed on the patient in the doctor's office when the doctor wishes
to read out stored telemetry or program one or more new parameters
into the implanted system. Furthermore, the cap could be used by
the patient at home for remote connection to the physicians
workstation over telephone lines using a pair of modems, or the cap
could be used to recharge a rechargeable battery located in the
control module of the implanted system.
[0035] Another important aspect of the system is a buzzer that can
be implanted just behind the ear on the outer or inner surface of
the cranium or actually within a burr hole within the cranium. If a
neurological event is detected, the buzzer can provide an acoustic
output that is detectable by the patient's ear or the buzzer can
provide an electrical "tickle" signal. The buzzer can be used to
indicate to the patient that a neurological event such as an
epileptic seizure is about to occur so that an appropriate action
can be taken. Among the appropriate actions that could be taken by
the patient is the application of an acoustic, visual or sensory
input that could by themselves be a means for stopping a
neurological event such as an epileptic seizure. The acoustic input
could be by means of a sound producing, hearing aid shaped device
that can emit an appropriate tone as to pitch and volume directly
into the ear. The visual device could be from a light emitting
diode in eyeglasses or a small flashlight type of device that emits
a particular type of light at some appropriate flashing rate. A
sensory input could be provided by, for example, an externally
mounted electrical stimulator placed on the wrist to stimulate the
median nerve or by a mechanical vibrator applied to the patient's
skin.
[0036] When any such acoustic, visual or other sensory input is
actuated, either automatically or manually in response to the
detection of a neurological event, literally billions of neurons
are recruited within the brain. The activation of these neurons can
be an effective means for stopping an epileptic seizure.
[0037] An alternative embodiment of the present invention envisions
the use of a control module located external to the patient's body
connected to electrodes either external or internal to the
patient's scalp. Such an externally located control module might be
positioned behind the patient's ear like a hearing aid.
[0038] Thus it is an object of this invention to provide
appropriate stimulation of the human brain in response to a
detected neurologic event in order to cause the cessation of that
neurologic event.
[0039] Another object of this invention is to provide increased
reliability for neurological event detection by the use of
cross-correlated signals from multiple electrodes with appropriate
time delay(s) to increase the sensitivity and reliability for
detection from a specific area of the brain.
[0040] Still another object of this invention is to exploit a
spectral characteristic of the signals from multiple electrodes to
optimize the detection of a neurological event.
[0041] Still another object of this invention is to predispose the
decision-making algorithm to allow false positives to cause a
responsive stimulation but to disallow missing an actual event.
[0042] Still another object of this invention is to have the
response to a neurological event be an electrical stimulation that
is focused on a specific area of the brain by variably delaying the
stimulation signal sent from each of several stimulation electrodes
placed at different locations placed in close proximity to the
brain or within the brain.
[0043] Still another object of this invention is to have the
specific area of the brain onto which the response is focused be
the area from which the event signal was detected.
[0044] Still another object, of this invention is to record (and
ultimately recover for analysis) the EEG signal(s) from one or more
electrodes before, during and after a neurological event.
[0045] Still another object of this invention is to provide
programmability for all-important operating parameters of the
device.
[0046] Still another object of this invention is to provide
recording of the certain functions of the device such as how many
neurological events were detected and how many times the device
responded to such detections.
[0047] Still another object of this invention is to use medication
delivery as the response to a neurological event, either alone or
in conjunction with electrical stimulation.
[0048] Still another object of this invention is to utilize
implanted electronic circuitry which is adaptable to changing EEG
input signals so as to provide self-adaptation for the detection
and/or treatment of a neurological event.
[0049] Still another object of this invention is to have a system
of electrodes connected by wires to a control module, the entire
system being placed under the scalp and being essentially contained
within the cranium.
[0050] Still another object of this system is to have essentially
no flexure of interconnecting wires so as to enhance system
reliability.
[0051] Still another object of this invention is to be able to
replace a depleted battery within the system's control module by a
comparatively simple and quick surgical procedure.
[0052] Still another object of this invention is to be able to
replace an electronics module within the system's control module by
a comparatively simple and quick surgical procedure.
[0053] Still another object of this invention is to be able to
recharge the battery in the control module.
[0054] Still another object of this invention is to provide an
externally situated patient's initiating device that can be used by
the patient when he or she senses that a neurological event is
about to occur in order to provide a response for causing the
stopping of that neurological event or in order to initiate the
recording of EEG signals from a pre-selected set of electrodes.
[0055] Still another object of this invention is to utilize a
remotely located sensor/actuator device within the body to detect
an abnormal physiological condition and send an electrical signal
with or without wires to a control module within the cranium which
then responds by an electrical signal delivered to the brain to
treat the abnormal physiological condition.
[0056] Still another object of this invention is to utilize an
intracranial system for sensing some abnormal physiological
condition and then sending an electrical signal with or without
wires to a remote sensor/actuator device that is remotely located
within the body to carry out some treatment modality.
[0057] Still another object of this invention is to provide a
buzzer which indicates to the patient that a neurological event has
occurred.
[0058] Still another object of this invention is to provide
acoustic, visual or other sensory inputs to the patient either
automatically or manually following the detection of a neurological
event so as to stop the neurological event.
[0059] These and other objects and advantages of this invention
will become apparent to a person of ordinary skill in this art upon
careful reading of the detailed description of this invention
including the drawings as presented herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0060] FIG. 1 is a top view of a human head showing the
configuration of an implantable system for the treatment of
neurological disorders as it would be situated in the human
skull.
[0061] FIG. 2 is a block diagram of the implanted and external
portions of the system.
[0062] FIG. 3 is a block diagram illustrating the event detection
sub-system which utilizes digital signal processing techniques that
can exploit either or both time and frequency domain information to
accomplish event detection.
[0063] FIG. 4 is a flow chart pertinent to the processing activity
carried on within the programmable digital signal processor which
is part of the event detection sub-system.
[0064] FIG. 5A illustrates the amplitude of the electrical signal
received at FIFO memory 344A as a function of time.
[0065] FIG. 5B illustrates the amplitude of the electrical signal
received at FIFO memory 344B as a function of time.
[0066] FIG. 5C illustrates the amplitude of the electrical signal
received at FIFO memory 344C as a function of time.
[0067] FIG. 5D illustrates the sum of the time delayed signal
amplitudes showing also that the event detection threshold is
exceeded at -20 milliseconds.
[0068] FIG. 6 illustrates a block diagram for an alternative
algorithm for detection of a neurological event which uses the
amplitude differences of signals from pairs of electrodes.
[0069] FIG. 7 is a flow chart of the event recording and processing
which is carried on within the event processing microcomputer used
for the second stage of an event detection sub-system.
[0070] FIG. 8 illustrates the recording of EEG and /or EEG spectrum
signals by the central processor.
[0071] FIG. 9 shows a flow chart of the central processor function
for: (1) receiving event detection information from the event
detection sub-system; (2) sending delay and threshold parameters to
the event processing microcomputer and digital signal processor;
(3) storing event related data; (4) inducing responsive brain
stimulation through the stimulation sub-system; and (5)
communicating externally for physician data read out and system
programming.
[0072] FIG. 10 is a block diagram of the stimulation sub-system as
used to stimulate the brain responsive to a detected event.
[0073] FIG. 11 is a block diagram of the data communication
sub-system and external data interface.
[0074] FIG. 12 is a block diagram of a hybrid analog/digital
representation of the event detection sub-system using time domain
information for event detection.
[0075] FIG. 13 is a block diagram of a hybrid analog/digital
representation of the event detection sub-system using frequency
domain information for event detection.
[0076] FIG. 14 is a block diagram of an implantable system that can
respond to a detected neurological event by infusing medication
into the patient's body.
[0077] FIG. 15 is a top view of a human head showing the
arrangement of a multiplicity of electrodes connected by wires to a
control module that is implanted within the cranium.
[0078] FIG. 16 is a side view of a human head showing the
arrangement of one surface and one deep electrode connected by
wires that pass through a hole in the cranium and connect to a
control module that is implanted within the cranium.
[0079] FIG. 17 is a top view of a human head showing the
arrangement of an implanted input-output flat wire coil connected
by wires to a control module that is implanted within the
cranium.
[0080] FIG. 18 is a side view of a human head showing the
arrangement of the implanted input-output flat wire coil as it
would be used with a patient's initiating device to trigger some
operation of the implanted system.
[0081] FIG. 19 is a side view of a human head showing the
arrangement of the implanted input-output coil as it would be used
with a cap and with the physician's external equipment to perform
some interaction with the implanted system.
[0082] FIG. 20 is a top view of the shell of the control
module.
[0083] FIG. 21 is a cross section of the cranium showing a control
module placed essentially within the cranium within a space where
cranium bone has been removed. The cross section of the shell in
FIG. 21 is taken along the section plane 21-21 of FIG. 20.
[0084] FIG. 22 is a side view of the human head and torso showing
an alternative embodiment of the present invention using a control
module implanted within the chest.
[0085] FIG. 23 is a side view of the human head and torso showing
an alternative embodiment of the present invention using a control
module implanted between the scalp and the cranium, a remote
sensor/actuator device located within the chest, and external
devices for applying acoustic, visual, or other sensory input to
the patient.
[0086] FIG. 24 is a side view of a human head showing alternative
communication means between the external equipment and an implanted
control module and also showing alternative locations for
electrodes mounted in close proximity to the patient's brain.
[0087] FIG. 25 is a side view of the human head and torso showing
an alternative embodiment of the present invention using a control
module located external to the patient's body and a remote
sensor/actuator device located within the chest, and external
devices for applying acoustic, visual, or other sensory input to
the patient.
DETAILED DESCRIPTION OF THE DRAWINGS
[0088] FIG. 1 illustrates the configuration of an implantable
system 10 for the treatment of neurological disorders as it would
be situated under the scalp of a human head 9 having a control
module 20, electrodes 15A, 15B, 15C, 15N and 16 with wires 17A,
17B, 17C, 17N and 18 connected through the connector 8 to the
control module 20. It is envisioned that the control module 20 is
permanently implanted into the top of the skull in a location where
the skull is fairly thick. It is also envisioned that the control
module 20 could be located in the trunk of the patient's body like
a heart pacemaker with the connecting wires being run under the
patient's skin. The electrodes 15A, 15B, 15C, 15N and 16 would be
placed under the cranium and above the dura mater (i.e., placed
epidurally) or placed deep into the brain. The connecting wires
17A, 17B, 17C, 17N and 18 would be run from the control module 20
underneath the scalp and then be connected to the electrodes placed
beneath the patient's cranium. Although FIG. 1 shows only 4 active
electrodes 15A, 15B, 15C, 15N with connecting wires 17A, 17B, 17C,
17N, more than 4 active electrodes with connecting wires may be
used with the present invention. The electrode 16 (having a
connecting wire 18) could be considered a common or indifferent
electrode.
[0089] Throughout the detailed description of the present
invention, the terminology "the electrodes 15A through 15N" is
meant to include all electrodes 15A, 15B, 15C, . . . to 15N
inclusive where N may be any integer between 1 and 200. Similar
terminology using the words "through" or "to" for other groups of
objects (i.e., wires 17A through 17N) will have a similar inclusive
meaning.
[0090] Throughout FIGS. 1 through 25 inclusive, lines connecting
boxes on block diagrams or on software flow charts will each be
labeled with an element number. Lines without arrows between boxes
and/or solid circles indicate a single wire.
[0091] Lines with arrows connecting boxes or circles are used to
represent any of the following:
[0092] 1. A physical connection, namely a wire or group of wires
(data bus) over which analog or digital signals may be sent.
[0093] 2. A data stream sent from one hardware element to another.
Data streams include messages, analog or digital signals, commands,
EEG information, and software downloads to change system operation
and parameters.
[0094] 3. A transfer of information between software modules. Such
transfers include software subroutine calls with and without the
passing of parameters, and the reading and writing of memory
locations.
[0095] In each case, the text will indicate the use of the line
with an arrow.
[0096] FIG. 2 is a block diagram of the implantable system 10 and
the external equipment 11. The wires 17A through 17N from the
electrodes 15A through 15N, and the wire 18 from the common
electrode 16, are shown connected to both the event detection
sub-system 30 and the stimulation sub-system 40. It is also
envisioned to use the case of the control module 20 of FIG. 1 as
the common (or indifferent) electrode 16. The wires 17A through 17N
carry EEG signals 21A through 21N from the electrodes 15A through
15N to the event detection sub-system 30. The electrodes 15A
through 15N can be energized by the stimulation sub-system 40 via
the wires 17A through 17N to electrically stimulate the patient's
brain using the stimulation signals 412A through 412N respectively.
Although the electrodes 15A through 15N and 16 shown here are
connected to both the event detection sub-system 30 and the
stimulation sub-system 40, it is obvious that a separate set of
electrodes and associated wires could be used with each sub-system.
Furthermore, it is envisioned that any one, several or all of the
electrodes 15A through 15N could be electrically connected (i.e.,
shorted) to the electrode 16 or to each other. This would be
accomplished by appropriate switching circuitry in the stimulation
sub-system 40.
[0097] The event detection sub-system 30 receives the EEG signals
21A through 21N (referenced to system ground 19 connected to the
wire 18 from the common electrode 16) and processes them to
identify neurological events such as an epileptic seizure or its
precursor. A central processing system 50 with central processor 51
and memory 55 acts to control and coordinate all functions of the
implantable system 10. The interconnection 52 is used to transmit
programming parameters and instructions to the event detection
sub-system 30 from the central processing system 50. The
interconnection 53 is used to transmit signals to the central
processing system 50 identifying the detection of a neurological
event by the event detection sub-system 30. The interconnection 53
is also used to transmit EEG and other related data for storage in
the memory 55.
[0098] When an event is detected by the event detection sub-system
30, the central processor 51 can command the stimulation sub-system
40 via the interconnection 54 to transmit electrical signals to any
one or more of the electrodes 15A through 15N via the wires 17A
through 17N. It is anticipated that, if appropriate electrical
signals 412A to 412N inclusive are transmitted to certain locations
in or near the brain, the normal progression of an epileptic
seizure can be aborted. It may also be necessary for the
stimulation sub-system 40 to temporarily disable the event
detection sub-system 30 via the interconnection 29 when stimulation
is imminent so that the stimulation signals are not inadvertently
interpreted as a neurological event by the event detection system
30.
[0099] A power supply 90 provides power to each component of the
system 10. Power supplies for comparable implantable devices such
as heart pacemakers and heart defibrillators are well known in the
art of implantable electronic devices. Such a power supply
typically utilizes a primary (non-rechargeable) storage battery
with an associated d-c to d-c converter to obtain whatever voltages
are required for the implantable system 10. However, it should be
understood that the power supply could use a rechargeable battery
that is charged by means of a coil of wire in the control module 20
that receives energy by magnetic induction from an external coil
that is placed outside the patient but in close proximity to the
control module. The implanted coil of wire could also be located
remotely from control module 20 but joined to it by electrical
wires. Such technology is well known from the rechargeable cardiac
pacemaker. Furthermore, the same pair of coils of wire could be
used to provide power to the implanted system 10 when it is desired
to read out stored telemetry or reprogram some portion of the
implanted system 10.
[0100] Data stored in the memory 55 can be retrieved by the
patient's physician by a wireless communication link 72 with the
data communication sub-system 60 connected to the central
processing system 50. An external data interface 70 can be directly
connected with an RS-232 type serial connection 74 to the
physician's workstation 80. Alternately, the serial connection may
be via modems 85 and 750 and phone line 75 from the patient's home
to the physician's workstation 80. The software in the computer
section of the physician's work station 80 allows the physician to
read out a history of events detected including EEG information
both before, during and after the event as well as specific
information relating to the detection of the event such as the time
evolving energy spectrum of the patient's EEG. The workstation 80
also allows the physician to specify or alter the programmable
parameters of the implantable system 10.
[0101] As shown in FIGS. 1 and 2, a buzzer 95 connected to the
central processor 51 via the link 92 can be used to notify the
patient that an event has occurred or that the implanted system 10
is not functioning properly. The buzzer could provide a mechanical
vibration (typically an acoustic signal) or an electrical
stimulation "tickle" either of which could be perceived by the
patient. By placing the buzzer 95 near the ear and on the top of,
below, or within a burr hole in the cranium, an acoustic signal
emitted by the buzzer 95 will be detectable by the patient's ear.
This sound by itself can be an automatic means for stopping an
epileptic seizure.
[0102] A real time clock 91 is used for timing and synchronizing
various portions of the implanted system 10 and also to enable the
system to provide the exact date and time corresponding to each
neurological event that is detected by the implantable system 10
and recorded in memory. The interconnection 96 is used to send data
from the central processor 51 to the real time clock 91 in order to
set the correct date and time in the clock 91.
[0103] The various interconnections between sub-systems (e.g., the
interconnections 52, 53, 54, 56, 57, 92, 93 and 96) may be either
analog or digital, single wire or multiple wires (a "data
bus").
[0104] The operation of the system 10 of FIG. 2 for detecting and
treating a neurological event such as an epileptic seizure would be
as follows:
[0105] 1. The event detection sub-system 30 continuously processes
the EEG signals 21A through 21N carried by the wires 17A through
17N from the N electrodes 15A through 15N.
[0106] 2. When an event is detected, the event detection sub-system
30 notifies the central processor 51 via the link 53 that an event
has occurred.
[0107] 3. The central processor 51 then triggers the stimulation
sub-system 40 via the link 54 to electrically stimulate the
patient's brain (or electrically short some electrodes or release
medication) in order to stop the neurological event using any one,
several or all of the electrodes 15A through 15N.
[0108] 4. The stimulation sub-system 40 also sends a signal via the
link 29 to the event detection sub-system 30 to disable event
detection during stimulation to avoid an undesired input into the
event detection sub-system 30.
[0109] 5. The central processor system 50 will store EEG signals
and event related data received from the event detection sub-system
30 via the link 53 over a time from X minutes before the event to Y
minutes after the event for later analysis by the patient's
physician. The value of X and Y may be set from as little as 0.1
minutes to as long as 30 minutes.
[0110] 6. The central processor 51 may "buzz" to notify the patient
that an event has occurred by sending a signal via the link 92 to
the buzzer 95.
[0111] FIG. 3 is a block diagram illustrating an implementation of
the event detection sub-system 30 using digital signal processing
techniques. The event detection sub-system 30 can use either or
both, time and frequency domain information for event detection.
The event detection sub-system 30 receives the signals 21A through
21N from the wires 17A through 17N and processes them to identify
the early stages of a neurological event such as an epileptic
seizure. The signals 21A through 21N are amplified by the
amplifiers 32A through 32N respectively, to produce the amplified
EEG signals 22A through 22N. The amplifiers 32A through 32N can
also provide low pass and/or high pass filtering to remove unwanted
noise. Each amplifier 32A through 32N can be disabled by a signal
placed on interconnection 29 from the stimulation sub-system 40
during brain stimulation so as to prevent overloading the
amplifiers or creating an undesired input signal into the event
detection sub-system 30.
[0112] The amplified EEG signals 22A through 22N are then digitized
by the analog-to-digital converters 33A through 33N producing the
digitized EEG signals 23A through 23N which are processed by the
programmable digital signal processor 34 with associated memory 35
to enhance the signal-to-noise ratio for the detection of
neurological events. Processed signals 24 are then passed to the
event processing microcomputer 36 with associated memory 37 for
analysis with the goal of achieving event detection. When the event
processing microcomputer 36 identifies an event, it produces a
detection signal which it sends along with stored EEG and EEG
energy spectral data streams to the central processor 51 through
the interconnection 53. The central processor 51 can pass specific
program parameters and revised programming instructions to the
event processing microcomputer 36 via the interconnection 52. The
event processing microcomputer 36 can also pass any appropriate
program parameters and revised programming instructions received
from the central processor 51 on to the programmable digital signal
processor 34 via the interconnection 25. This scheme provides
patient-specific optimization of event detection algorithm(s). For
example the program might look at signal amplitude differences
between certain electrodes, or alternately, event detection might
be based on analysis of a signal created by adding the signals
(possibly with varying time delays) derived from a specific subset
of the electrodes. It is also possible that the programmable
digital signal processor 34 might be programmed to perform both
digital signal processing and event processing thus not requiring a
separate event processing microcomputer 36. It is also envisioned
that the event processing microcomputer 36 and the central
processor 51 may be the same microcomputer having separate
subroutines in software for each function.
[0113] The amplifiers 32A through 32N, the analog-to-digital
converters 33A through 33N and the programmable digital signal
processor 34 each separately and collectively constitute a signal
conditioning means for processing the EEG signals 21A through 21N.
The event processing microcomputer 36 provides event detection
means for the detection of a neurological event.
[0114] Integrated circuit amplifiers, analog-to digital converters,
digital signal processors (DSPs), digital memory and microcomputers
and the techniques to interconnect and program them are well known
in the art. Custom VLSI or hybrid circuits could be developed that
would combine certain functions.
[0115] FIG. 4 is a flow chart pertinent to the processing activity
340 carried on within the programmable, digital signal processor 34
of the event detection sub-system 30. The digitized EEG signals 23A
through 23N are first processed by the step of removing any d-c
bias by the subroutines 341A through 341N producing digital signals
351A through 351N which are then processed by the automatic gain
control (AGC) subroutines 342A through 342N to produce the AGC EEG
signals 352A through 352N. These AGC EEG signals 352A through 352N
would then be free of any d-c bias, and be of identical maximum
amplitude during that time when the brain is not experiencing a
neurological event. The purpose of AGC is to remove the variation
in EEG signal amplitude which can change slowly over a period of a
few hours. Thus the AGC subroutines 342A through 342N might adjust
the amplitude of incoming signals 351A through 351N based on the
average energy detected over a period of several minutes. However,
a rapidly changing signal such as that from a neurological event
would not have their amplitudes modified by the AGC subroutines
342A through 342N.
[0116] Using the step of AGC at this stage of the processing will
allow the use of a constant threshold for event identification at a
later stage. The AGC time constant is among the programmable
parameters that can be programmed in the DSP program instructions
348 that are passed via the interconnection 25 from the event
processing microcomputer 36. AGC algorithms which adjust the output
gain based on time averaged energy are well known in the art and
can be implemented by an experienced DSP programmer. It is also
envisioned that the amplifiers 32A through 32N of FIG. 3 might be
analog AGC amplifiers so that a DSP AGC algorithm would be
unnecessary. AGC is an example of a self-adaptive algorithm used by
the event detection subsystem 30.
[0117] The processed EEG signals 352A through 352N are continuously
passed via the interconnections 24 to the event processing
microcomputer 36 so that they may be stored for later physician
analysis if a neurological event occurs. The processed EEG signals
352A through 352N are also processed further by additional signal
conditioning steps to enhance event identification. These steps
involve first squaring the signals 352A through 352N using the
squaring subroutines 343A through 343N to produce the squared EEG
signals 353A through 353N. The squared EEG signals 353A through
353N are fed into the First-In-First-Out (FIFO) buffers 344A
through 344N where between 1 and 100 milliseconds of data can be
stored. Implementing FIFO data storage in DSP software is well
known and can be implemented by an experienced DSP programmer.
[0118] Epileptic seizures and many other neurological events can
originate in a comparatively small section of the brain called an
epileptic focus. A preferred embodiment of the digital signal
processing algorithm 340 for event detection is based on the
principle that the signals arriving at the electrodes 15A through
15N (shown in FIG. 2) from an epileptic focus will always do so
with essentially the same time delay for each electrode. Or stated
another way, the propagation time required for a signal to travel
from the epileptic focus to an electrode will be consistently as
follows: t.sub.1 milliseconds for a electrode 15A, t.sub.2
milliseconds for electrode 15B, t.sub.3 milliseconds for electrode
15C, etc., where t.sub.1, t.sub.2, t.sub.3 . . . do not
significantly change in value from time-to-time. The FIFOs 344A
through 344N are nothing more than a digital equivalent of a delay
line where the sum with delay algorithm 345 can elect to sample the
squared EEG signals 353A through 353N with each delayed
appropriately to create the time synchronized EEG signals 354A
through 354N which are summed by the sum with delay algorithm 345.
The sum with delay algorithm 345 will produce the sum of time
synchronized squared signals 355. EEG signals originating from
parts of the brain away from the focus will not be synchronized by
the algorithm 345 whose time delays are set to synchronize EEG
signals originating at the focus. Thus the amplitude of the sum of
time synchronized squared signals 355 will be much larger for EEG
signals originating at the focus.
[0119] The delays for each of the FIFO buffers are programmed
through the DSP program instructions 348. The settings for FIFO
time delays would be derived from analysis of recorded EEG signals
during events from a patient having the same electrode
configuration to be used for event detection. Interconnection 25 is
the interconnection over which the programming instructions 348 are
provided by the event processing microcomputer 36 to set the time
delay parameters for the FIFO buffers.
[0120] The signal 355 can be sent to the event processing
microcomputer 36 for time domain event detection. The signal 355
can also be transformed into the frequency domain by the transform
algorithm 346, which will produce a frequency spectrum that can
change with time having frequency band signals 356-1, 356-2, 356-3,
356-4 through 356-M which are the time evolving signals
corresponding to a total of M frequency bands (band 1 through band
M). The frequency band signals 356-1 through 356-M are digital data
streams, each representing the energy of the signal 355 in the
corresponding frequency band (band 1 through band M). An example of
such frequency bands is as follows: (a) band 1:1 to 2 Hz; (b) band
2:2 to 4 Hz; (c) band 3:4 to 8 Hz; etc. The specific division of
the bands is programmable through the DSP programming instructions
348 and may be derived for each patient from analysis of recorded
EEG information. The frequency band signals 356-1 through 356-M are
sent to the event processing microcomputer 36 for the purpose of
event detection.
[0121] FIGS. 3 and 4 illustrate one embodiment of a multiple step
signal conditioning means for the EEG signals 21A through 21N. The
specific steps used in this embodiment are amplification,
analog-to-digital conversion, adjustment of d-c offset, AGC,
squaring, time delaying, summing and frequency transformation. The
ability to program the programmable digital signal processor 34 to
implement any combination of these or other steps in any order to
enhance event detection for each patient is an important aspect of
the event detection sub-system 30.
[0122] FIGS. 5A, 5B and 5C show the signal traces for a 3 electrode
implementation of the present invention with the squared EEG
signals 353A, 353B and 353C stored in the FIFOs 344A, 344B and 344C
respectively. In this example, the FIFOs 344A, 344B and 344C store
100 milliseconds of data consisting of 20 samples each, with each
sample being the average value for a period of 5 milliseconds of
the squared EEG signals 353A, 353B and 353C. The last data placed
in the FIFOs 344A, 344B, and 344C correspond to time equals zero,
and are the most recent samples of the squared EEG signals 353A,
353B and 353C.
[0123] During pre-implant data recording and analysis of a
patient's EEG data, the relative delays between EEG signals from an
epileptic focus arriving at electrodes 15A, 15B and 15C would be
calculated. In this example, the electrode 15A from which the data
in FIFO 344A originates, is the last to receive the EEG signal from
such an event. The time delay parameter 358A for the electrode 15A
is therefore set to 0. In this example, electrode 15B which is the
source of data for FIFO 344B, is known to receive an event signal
15 ms before electrode 15A thus the time delay parameter 358B for
electrode 15B is set to 15 ms. Similarly, electrode 15C from which
the data in FIFO 344C receives an event signal 35 ms before
electrode 1SA; thus the signal delay parameter 358C for electrode
15C is set to 35 ms.
[0124] Using the time delay parameters 358A, 358B and 358C, the
specific samples 354A, 354B and 354C (marked with the black arrows
6A, 6B and 6C) are fed into the sum with delay algorithm 345. The
sum with delay algorithm 345 adds these specific FIFO samples
together to produce the signal 355 as shown in FIGS. 4 and 5D. FIG.
5D shows the current sample of the signal 355 and the last 100
milliseconds of the signal 355 created by the sum with delay
algorithm 345.
[0125] A simple means to detect, a neurological event using the sum
with delay algorithm 345 with resulting signal 355 is to compare
the signal 355 with a fixed event detection threshold 369 as shown
in FIG. 5D. The threshold 369 is exceeded at times 0, -10 ms and
-20 ms. This methodology can be an effective means for event
detection when used in conjunction with the automatic gain control
algorithms 342A, 342B and 342C as shown in FIG. 4. The automatic
gain control has the effect which is seen in FIGS. 5A through 5C of
keeping the samples of the squared EEG signals below the AGC limits
362A, 362B and 362C which limits are programmed into the automatic
gain control algorithms 342A, 342B and 342C shown in FIG. 4. The
AGC subroutines 342A, 342B and 342C might adjust the amplitude of
the EEG signals 352A through 352N based on the average energy
detected over a period of several minutes so that a rapidly
changing signal such as that from a neurological event will not be
affected.
[0126] It is also envisioned that the delay parameters 358A, 358B
and 358C may be self-adaptive so that when an event is detected,
post-analysis by the digital signal processor 34 using the data
stored in the FIFOs 344A, 344B and 344C can determine if adjusting
the delays 358B and 358C plus or minus in time would increase or
decrease the sum of the time synchronized squared EEG signals 355.
If the signal 355 increases by a shift of the time delay 358B or
358C, then the delay parameters 358B and 358C could be
automatically changed to increase the sensitivity for future event
detection. This example of the capability to modify it's own
operating parameters is an example of self-adaptation of the
programmable digital signal processor 34. It is also envisioned
that other programmable components of the system 10 of FIG. 2 other
than the event detection sub-system 30 may be self-adaptive to be
capable of optimizing system operability without external
commands.
[0127] Although FIGS. 5A-5D show the signals relating to an
implementation of the present invention using 3 signal electrodes,
the algorithms described can be applied to any set of 2 or more
signal electrodes.
[0128] It is also envisioned that instead of delaying the signals
from each electrode to provide time synchronization, the electrodes
might be placed at positions where the time delays from an
epileptic focus to each electrode could be the same. Furthermore,
it is envisioned that instead of squaring the value of the EEG
signal amplitude, which is done to eliminate a zero average over a
certain period of time, the same objective could be accomplished by
rectification of the EEG signal.
[0129] FIG. 6 shows an embodiment of the present invention in which
the digital signal processor processing 440 based on DSP program
instructions 448 takes the digitized EEG signals 23A, 23B, 23C and
23D from four brain electrodes 15A, 15B, 15C and 15D and creates
the difference signal 424 from signals 23A and 23B using the
subtraction algorithm 434, and the difference signal 425 from
signals 23C and 23D using the subtraction algorithm 435. The
difference signals 424 and 425 can then be multiplied by weighting
factor algorithms 436 and 437 to adjust for difference in signal
level for events arriving at each pair of electrodes. The resulting
weighted differential EEG signals 426 and 427 are summed by the
algorithm 438 to create the summed differential EEG signal 428. The
summed differential EEG signal 428 can then be transformed into a
set of frequency band signals 456-1 through 456-M by the algorithm
446 as previously described with respect to the digital signal
processing 340 shown in FIG. 4.
[0130] The embodiment of FIG. 6 will work best when the electrode
pairs 15A-15B and 15C-15D are located in positions that will cause
the EEG signal differences 424 and 425 to be synchronized in time
for EEG signals originating at the focus of a neurological event.
It is also envisioned that a programmable delay adjustment, as
described for FIG. 4, could be implemented here if the time delays
for EEG signal differences 424 and 425 from a neurological event
are not the same.
[0131] The summed differential EEG signal 428, the difference EEG
signals 424 and 425, and the frequency band signals 456-1 through
456-M can be sent via interconnection 24 to the event processing
microcomputer 36 for storage.
[0132] It is also envisioned that instead of digitizing the signal
from each signal electrode 15A through 15N, with respect to a
common electrode 16, the input stage could use any one or more
pairs of brain electrodes with no single common electrode.
[0133] The processing 340 of FIG. 4 and 440 of FIG. 6 are examples
of two different implementations of multiple step signal
conditioning programs which can be run within the programmable
digital signal processor 34 of FIGS. 2 and 3.
[0134] FIG. 7 shows the software flow chart for event recording and
processing 360 of the event processing microcomputer 36 used for
the second stage of the event detection sub-system 30 shown in
FIGS. 2 and 3. Specifically, event recording and processing 360
represents the algorithms and subroutines in software used by the
event processing microcomputer 36 (hardware) as the event detection
means and also to record relevant EEG and spectral band data. A
primary objective of event recording and processing 360 software is
to make possible the recording of AGC modified EEG signals 352A
through 352N inclusive and the frequency band signals 356-1 to
356-M inclusive by the central processing system 50.
[0135] FIG. 8 indicates that the central processing system 50 is
capable of recording EEG and frequency band data for "X" minutes
before a neurological event is detected and "Y" minutes after the
neurological event is detected. The event recording and processing
360 of FIG. 7 is used to facilitate this data recording capability.
Specifically, the EEG signals 352A through 352N (also see FIG. 4)
are stored in data FIFO memories 363A through 363N. If an event is
detected, the FIFOs 363A through 363N can be read by the central
processor 51 via the link 53 to retrieve the stored EEG data
streams 373A through 373N for a time "X" minutes before the event.
The central processor 51 can also read the data FIFOs 363A through
363N in real time after detection of a neurological event for a
period of "Y" minutes. Alternatively the data FIFOs 363A through
363N could be used to store and then read out "Y" minutes of data
stored after the event is detected. In either case, the goal of
retrieving "X" minutes of pre-event detection data and "Y" minutes
of post-event detection data (as indicated in FIG. 8) can be
achieved. It should be remembered that if there are N electrodes
then there will be as many as N channels of AGC modified EEG data
that can be recorded. However, the central processing system 50 may
be programmed to record EEG data from a sub-set of the electrodes
15A through 15N (see FIG. 2). All data stored by the central
processing system 50 can be retrieved by the patient's doctor for
analysis with the goal of improving the response of the system 10
so as to more reliably stop a neurological event.
[0136] FIG. 7 also shows two different schemes for detecting an
event. If the amplitude of the sum of the time synchronized squared
EEG signals 355 exceeds the event detection threshold 369 as shown
in FIG. 5D (using threshold detector algorithm 368 of FIG. 7), the
algorithm 368 sends a positive event detected message 358 to the
event density counter/detector algorithm 371. The event density
counter/detector algorithm 371 determines if there have been enough
events in the most recent time period "T" to notify the central
processor 51 with the event identified message 372 indicating that
an event has really occurred. A typical time period "T" would be
approximately 2 seconds but could be in the range from 1/2 to 100
seconds. The event density counter/detector algorithm 371 will
reduce the number of false positive event identifications by
eliminating short uncorrelated EEG bursts. If the number of events
in the time period "T" is set equal to 1, then the system will be
most sensitive and any time sample which exceeds the threshold 369
in the threshold detector algorithm 368, will be passed on as an
event identified message 372. A typical setting for the number of
events for a two second time period "T" would be four.
[0137] The system for detecting a neurological event based on the
threshold detector 368 would involve processing data for the entire
frequency spectrum of the sum of the time synchronized and squared
EEG signals 355. As shown in FIG. 4 the signal 355 can be
transformed into a set of frequency band signals 356-1 through
356-M inclusive each of which signals is of limited bandwidth as
compared with the broadband signal 355. Each of the frequency band
signals 356-1 through 356-M of FIG. 7 can be analyzed by a
threshold detector algorithm 367-1 through 367-M respectively in a
manner exactly analogous to the threshold detector algorithm 368
used to detect events from the broadband signal 355.
[0138] In a manner analogous to the threshold detector algorithm
368, each of the set of threshold detector algorithms 367-1 through
367-M can send a positive event detected signal 357-1 through 357-M
to a corresponding frequency band event density counter/detector
369-1 through 369-M when the amplitude of the frequency band signal
356-1 through 356-M exceeds a preset threshold level. The frequency
band event density counter/detectors 369-1 through 369-M will,
analogous to the event density counter/detector 371, determine if
there are a sufficient number of events per time period "T" in any
of the bands 1 through M to send an event identified message 359-1
through 359-M to the central processor 51 indicating that a
neurological event has occurred.
[0139] Analogous to the storage of the AGC modified EEG signals
352A through 352N by the data FIFOs 363A through 363N, each of the
M frequency band signals 356-1 through 356-M is stored in FIFO
memories 366-1 through 366-M, so that if an event is detected, the
FIFOs can be read by the central processing system 50 via the link
53 to retrieve the frequency band data streams 376-1 through 376-M
for a time "X" before event detection until some time "Y" after
event detection. As previously described, FIG. 8 illustrates this
concept for data storage.
[0140] Constructing computer code to store and retrieve sampled
digital signals from FIFO memory is well known in the art of
software design. Comparing an input signal amplitude against a
preset threshold, determining the number of counts per unit time
and comparing the counts per unit time against a preset number of
counts per unit time are also well known in the art of software
design.
[0141] It should be understood that the software which is the
digital signal processor processing 340 (see FIG. 4) is run by the
programmable digital signal processor 34 according to the DSP
program instructions 348. In a similar manner, the software for
event recording and processing 360 (see FIG. 7) is run by the event
processing microcomputer 36 of FIG. 4 according to the program
instructions for DSP and event processing 375. Additionally the
programming instructions for DSP and event processing 375 serves as
a pass through for the DSP program instructions 348 of FIG. 4. The
program instructions for DSP and event processing 375 are received
by the event processing microcomputer 36 (using the software for
event recording and processing 360) from the central processor 51
via the interconnection 52. The DSP program instructions 348 (see
FIG. 4) are received over interconnection 25 by the digital signal
processor 34 from the program instructions for DSP processing and
event processing 375 of FIG. 7.
[0142] The thresholds to be used for detection by the threshold
detector algorithms 368 and 367-1 through 367-M and the required
event densities for event identification by the event density
counter/detector algorithms 371 and 369-1 through 369-M, will
typically be programmed to minimize the chance of missing a "real"
neurological event even though this could result in the occasional
false positive identification of an event. This bias toward
allowing false positives might typically be set to produce from 1/2
to 5 times as many false positives as "real" events.
[0143] It is also envisioned that the software for event recording
and processing 360 might not require a separate microcomputer but
could operate either as a set of subroutines in the central
processor 51 or a set of subroutines in the programmable digital
signal processor 34.
[0144] It is also envisioned that the event recording and
processing software 360 could be programmed to provide an event
detection means based on detecting specific aspects of the waveform
of either time or frequency domain outputs of the signal
conditioning by the digital signal processor 36. Such aspects of
the waveform could include pulse width, first derivative or
waveform shape.
[0145] FIG. 9 shows a flow chart of the software for central
processor processing 510 as run by the central processor 51 of FIG.
2. The central processor 51 receives event detection messages 372
and 359-1 through 359-M, EEG data streams 373A through 373N and the
frequency band data streams 376-1 through 376-M from the event
processing microcomputer 36. The central processor 51 of FIG. 2
also sends and receives data to and from the data communication
sub-system 60 via interconnections 56 and 57. The processing 510
processes these messages, signals, and data streams.
[0146] Algorithm 514 receives the event detection messages 372 and
359-1 through 359-M provided by the event processing microcomputer
36 via the link 53. When the algorithm 514 receives such a message
indicating that a neurological event has occurred, the algorithm
514 calls the subroutine 512. The calling of the subroutine 512 by
the algorithm 514 is indicated by the element 515. The subroutine
512 reads and saves to the central processor's memory 55 via the
link 518, the last X minutes of stored EEG data streams 373A
through 373N and frequency band data streams 376-1 through 376-M
from the event processing microcomputer 36. The algorithm 512 will
continue to read and save to the central processor's memory 55, the
next "Y" minutes of EEG data streams 373A through 373N and
frequency band data streams 376-1 through 376-M from the event
processing microcomputer 36. As seen in FIG. 8, these data streams
may include a blank period during stimulation followed by data
which can be analyzed to determine the efficacy of the treatment.
The algorithm 514 also causes a signal 511 to be sent to the
stimulation sub-system 40 via the link 54 to cause the stimulation
sub-system 40 to respond as programmed to stop, the neurological
event.
[0147] Values for X and Y will typically be several minutes for X
and as much as a half-hour for Y. The memory 55 must be large
enough for at least one event and could be large enough to hold 10
or more events. The values X and Y like other parameters are
programmable and adaptable to the needs of each particular
patient.
[0148] The I/O subroutine 517 receives physician commands from the
data communication sub-system 60 via the link 56 and, in turn,
reads and sends back via the link 57 the data stream 519 containing
the event related data previously stored in the memory 55 by the
algorithm 512. These data are transmitted to the external equipment
11 by the data communication sub-system 60 via the wireless link 72
as shown in FIGS. 2 and 11.
[0149] The I/O subroutine 517 also plays a key role in the
downloading of software programs and parameters 59 to the
programmable sub-systems of the implantable system 10 of FIG. 2.
These programmable sub-systems include the event detection
sub-system 30, the central processing system 50 and the stimulation
sub-system 40. The programmable components of the event detection
sub-system 30 are the programmable digital signal processor 34 and
the event processing microcomputer 36 shown in FIG. 3. The
programming instructions and parameters 59 for the programmable
sub-systems 30, 40 and 50 are downloaded through the I/O subroutine
517 by the programming and parameters downloading subroutine 516 of
the central processor processing 510. The subroutine 516 stores the
instructions and parameters 59 and downloads the program
instructions for DSP and event processing 375 (also see FIG. 7) for
the event detection sub-system 30 via link 52 to the event
processing microcomputer 36. The subroutine 516 also downloads the
stimulation sub-system instructions and parameters 592 via the link
54 to the stimulation sub-system 40. The subroutine 516 also
updates the memory 55 with the programming instructions and
parameters 594 for the central processor processing 510.
[0150] Programmable microprocessors or self-contained
microcomputers, such as the Intel 8048 and 8051, which contain read
only memory for basic programs and random access memory for data
storage and/or program storage, can be used to implement the
central processor processing 510 as previously described. It is
also envisioned that a custom VLSI chip involving microprocessor,
signaling and memory modules could be produced specifically for
this application. All of the previously described algorithms to
store data, send notification signals and messages and make
decisions based on input data are straightforward for a software
programmer to implement based on the current state of the art.
[0151] It is also clear that current memory technology should be
suitable for EEG storage. For example, the EEG storage for a 4
electrode system using 8 bits (one byte) per sample at a sampling
rate of 250 samples per second (required for frequencies up to 125
Hz) will require 60,000 bytes per minute of data storage. Having
100 minutes of storage would require only 6 megabytes, which is
readily achievable using current memory chip technology. Thus if
both X and Y were each 1 minute, then a total of 50 neurological
events could be stored in the 6 megabyte memory.
[0152] It is also envisioned that with well known data compression
techniques such as adaptive pulse code modulation, the memory
requirements can be reduced significantly.
[0153] It should be understood that instead of using random access
memory to store the EEG data, non- volatile memory such as "flash
memory" could be used to conserve power.
[0154] FIG. 10 illustrates the stimulation sub-system 40 including
its interconnections to other sub-systems. The stimulation
sub-system 40 is used to stimulate the brain, responsive to a
detected event. The preferred embodiment of the stimulation
sub-system 40 comprises a delay processing microcomputer 420 and N
signal generators 422A through 422N attached to the electrodes 15A
through 15N by the wires 17A through 17N. The event detection
signal 511 from the central processor 51 is received by the delay
processing microcomputer 420 which first sends a signal via the
link 29 to the event detection sub-system 30 to shut down event
detection during stimulation. The delay processing microcomputer
420 will then feed stimulation command signals 410A through 410N to
the signal generators 422A through 422N for a specific
pre-programmed time period. The stimulation command signals 410A
through 410N may be simultaneous or may have a relative delay with
respect to each other. These delays can be downloaded by the
instruction and parameter download 592 from the central processor
51 via the link 54. It may be desirable that the delays be adjusted
so that the stimulation signals 412A through 412N from the signal
generators 422A through 422N reach the neurological event focus in
the brain at the same time and in-phase. This could enhance
performance of the stimulation sub-system 40 in turning off a
neurological event. Alternately, experience may indicate that
certain signals being out of phase when they arrive at the
neurological event focus may be particularly efficacious in
aborting a neurological event.
[0155] The stimulation command signals 410A through 410N can be
used to control the amplitude, waveform, frequency, phase and time
duration of the signal generators' output signals.
[0156] The typical stimulation signals 412A through 412N generated
by the signal generators 422A through 422N should be biphasic (that
is with equal energy positive and negative of ground) with a
typical frequency of between 30 and 200 Hz, although frequencies of
between 0.1 and 1000 Hz may be effective. It is also envisioned
that pure d-c voltages might be used, although they are less
desirable. If frequencies above 30 Hz are used, the signal
generators could be capacitively coupled to the wires 17A through
17N. The typical width of the biphasic pulse should be between 250
and 500 microseconds, although pulse widths of 10 microseconds to
10 seconds may be effective for a particular patient. Typical
voltages applied may be between 1 millivolt and 10 volts rms. The
stimulation would typically be turned on for several seconds
although times as short as a 1 millisecond or as long as 30 minutes
may be used.
[0157] Biphasic voltage generation circuits are well known in the
art of circuit design and need not be diagramed here. Similarly,
the code to have the delay processing microcomputer 420 provide
different command parameters to the signal generators 422A through
422N is easily accomplished using well known programming
techniques.
[0158] Although the delay processing microcomputer 420 is shown
here as a separate unit, it may be practical to have the central
processor 51 or the event detection microcomputer 36 of FIG. 3
provide the required processing. Consolidating many of the
processing functions within a single processor is practical with
the system 10 of FIG. 2 as the real time demands on any one system
typically occurs when the others are not extremely busy. For
example, during processing to identify an event, there is no need
for data I/O, EEG storage or stimulation. When an event is detected
and there is a need for EEG storage and stimulation, there is
reduced need for event detection processing.
[0159] It is also envisioned that the stimulation sub-system 40
could operate with only one electrode such as a single electrode
centrally located at an epileptic focus, or a deep electrode
implanted in the thalmus or the hippocampus of the brain. If this
were the case, the delay processing microcomputer 420 would not be
needed, and only a single signal generator circuit would be
required. By "located at an epileptic focus" it is meant that the
electrode would be placed within 2 centimeters of the center of
that focus.
[0160] FIG. 11 shows the block diagram of the data communication
sub-system 60 and the external data interface 70 including
interconnections to the central processor 51 and the physician's
work-station 80. When communication from the physician's
workstation 80 to the central processor 51 is desired, the antenna
730 of the external data interface is placed near the antenna 630
of the data communication sub-system 60. The workstation 80 is then
connected by the cable 74 to an RS-232 serial data interface
circuit 740 of the external data interface 70. The RS-232 serial
data interface circuit 740 connects to the RF transmitter 720 and
RF receiver 710 through the serial connections 722 and 712,
respectively. Alternatively, if the patient is remotely located
from the physician's workstation 80, the workstation 80 can be
connected to the RS-232 serial data interface over a dial-up
connection 75 using the modems 750 and 85.
[0161] Once the connection 74 or 75 has been established, wireless
signals 72 can sent to and from the RF transmitter/receiver pair
610 and 620 of the data communication sub-system 60 and the RF
transmitter/receiver pair 710 and 720 of the external data
interface 70. The wireless signals 72 are used to command software
updates via the link 612 through the serial-to-parallel data
converter 614 and the link 56 to the central processor 51. The
wireless signals 72 are also used to send stored data back through
the link 57 through the parallel-to-serial data converter 624
through the link 622 to the RF transmitter 620.
[0162] RF transceiver circuitry and antennas similar to this are
used in data communication with heart pacemakers and
defibrillators, and therefore, this technology is well known in the
art of implantable programmable devices. RS-232 interfaces, serial
to parallel and parallel to serial conversion circuits, are also
well known.
[0163] FIG. 12 is a block diagram of a hybrid analog/digital
embodiment of an event detection sub-system 130 that uses time
domain information for event detection. In this embodiment, analog
circuitry 139 is used to process and detect possible neurological
events, and digital logic circuitry 138 is used to check if the
density of possible events is sufficient to declare a "real" event.
As in FIG. 3, the incoming EEG signals 21A through 21N on wires 17A
through 17N are amplified by the amplifiers 131A through 131N which
may also provide band-pass or low-pass filtering and/or AGC of the
signals 21A through 21N resulting in the amplified signals 121A
through 121N which are then squared by the squarer circuits 132A
through 132N resulting in the squared signals 122A through 122N.
The squared signals 122A through 122N are then processed by a
series of analog delay line circuits 133A through 133N to create
the squared and time synchronized EEG signals 123A through 123N,
which are subsequently added together by the summing circuit 135.
The resulting summed time synchronized signal 125 is then fed into
a threshold detection circuit 136 which will output a digital pulse
126 whenever the summed time synchronized signal 125 exceeds a
pre-set threshold. The digital pulses 126 collected over time are
then processed by the digital logic circuit 138 to determine if the
event is real or not. The delay parameters 124A through 124N are
input to the delay lines 133A through 133N from the central
processor 151 and can be pre-set for a particular patient. Setting
the values for these time delays could be based on measured delays
of EEG signals received from an epileptic focus during diagnostic
testing of the patient using the implanted system 10 of FIG. 2.
During brain stimulation, a signal 129 is sent from the stimulation
sub-system 40 to shut down the amplifiers 131A through 131N to
avoid amplifier overload or mistakenly identifying a stimulation
signal as a neurological event signal.
[0164] Analog integrated circuits to multiply or sum analog signals
are commercially available. Integrated circuit bucket brigade
analog delay lines are also commercially available. It is also
envisioned that a hybrid circuit containing multipliers, summers
and delay lines could be produced to miniaturize the system 130. A
standard comparator circuit, also available as an integrated
circuit, can be used as the threshold detector 136 to compare the
signal 125 with a pre-set threshold. If the threshold is exceeded,
then a pulse is sent via the connection 126 from the threshold
detector circuit 136 to the event counter 141 of the digital logic
138.
[0165] The digital logic 138, which counts the number of event
pulses per second emitted by the threshold detector 136, can be
implemented using a simple programmable microcomputer similar to
that described for event recording and processing 360 shown in FIG.
7, or it can be implemented by a collection of standard digital
logic and counting circuitry. Such a set of circuitry could use a
counter 141 to count the possible event pulses 126 generated by the
threshold detector 136. An event detected pulse 128 would be
emitted by the counter 141 only when it overflows. If the counter
141 is reset once a second by a reset pulse 147 from an OR gate 146
which has been sent a pulse 144 from the clock 142, then only if
the counter 141 overflows in the one second time period between
reset pulses 147 will the event detected pulse 128 be generated.
Certain available counter chips can be reset to a preset number
rather than 0. In FIG. 12, the event counter 141 could be
implemented with such a counter chip so that a reset signal will
cause the counter to reset to a preset number 148 that would be set
via the connection 145 from the central processor 151. Thus, for
example, an 8 bit counter (which counts up to the number 256) could
be set to overflow when the number of pulses counted by the counter
141 causes it to count from the downloaded preset number 148 to the
number two hundred and fifty-six in less than one second. Of
course, times of less than 1 second or more than 1 second can also
be used for the time between the pulses 144 from the reset clock
142. The event detected pulse 128 is also used to reset both the
clock 142 and the event counter 141. An OR gate 146 will allow the
event counter 141 to be reset by either the pulse 144 from the
clock 142 or the event detected pulse 128. The processing by the
central processor 151 would be analogous to that shown in FIG.
9.
[0166] The specific threshold to be used for detection by the
threshold detector 136 and the preset 148 for the event counter 141
will typically be set to minimize the chance of missing a "real"
event even though this will result in occasional false positive
identification of an event.
[0167] FIG. 13 is a block diagram of a hybrid analog/digital
representation of still another embodiment of the event detection
sub-system 230 using frequency domain information for event
detection. In this embodiment, analog circuitry 239 is used to
process and detect possible events in each of M frequency bands.
Digital logic circuitry 238 is used to check if the density of
possible events is sufficient to declare a "real" event. The front
end (up through and including the sum 135) of the analog circuitry
239 of the sub-system 230 is identical to the front end of the
analog circuitry 139 of FIG. 12. As in FIG. 12, the incoming EEG
signals 21A through 21N on wires 17A through 17N are amplified by
the amplifiers 131A through 131N. These amplifiers 131A through
131N (which may also provide band-pass or low-pass filtering of the
signals 21A through 21N) produce the amplified signals 121A through
121N. The amplified signals 121A through 121N are then squared by
the squarer circuits 132A through 132N resulting in the squared
signals 122A through 122N. The squared signals 122A through 122N
are then processed by a series of analog delay line circuits 133A
through 133N to create the squared and time synchronized EEG
signals 123A through 123N, which are subsequently added together by
the summing circuit 135. The resulting summed time synchronized
signal 125 is fed to a set of analog band-pass filters 266-1
through 266-M for the M frequency bands. The resulting band signals
256-1 through 256-M are examined by the threshold detectors 267-1
through 267-M analogous to the threshold detector 136 of FIG. 12.
Each of the threshold detectors (267-1 through 267-M) will generate
a corresponding pulse (257-1 through 257-M) when a preset threshold
is exceeded analogous to the pulse 126 generated by the threshold
detector 136 of FIG. 12. The pulses 257-1 through 257-M are fed
into the event density counter/detectors 268-1 through 268-M each
identical to the digital logic circuit 138 of FIG. 12. The event
density counter/detectors 268-1 through 268-M will feed the
detected frequency band event pulses 258-1 through 258-M to the
central processor 251.
[0168] The central processor 251 processes events from event
density counter/detectors in a similar manner to the central
processor 151 of FIG. 12. The main differences are that the counter
presets 259-1 through 259-M may be different for each of the bands
as required to optimize sensitivity. During responsive brain
stimulation, a signal 129 is sent from the stimulation sub-system
40 to shut down the amplifiers 131A through 131N to avoid amplifier
overload or mistakenly identify a stimulation signal as an event
signal. The processing by the central processor 251 would be
analogous to that shown in FIG. 9.
[0169] FIG. 14 is a diagram of an implantable system 910 which can
respond to a detected neurological event by infusing medication
from an implantable medication system 91 into the patient's body
through the hollow catheter 93. The system 910 is identical to the
system 10 of FIG. 2 except that the programmable drug delivery
sub-system 91 replaces the stimulation sub-system 40 of FIG. 2 as
the sub-system which provides the response to an neurological event
detected by the event detection sub-system 30. In this embodiment,
the signal indicating that an event has been detected and the
programming instructions for the implantable drug delivery system
91 are transmitted via the link 96 from the central processor 51.
It may be desirable to place the outlet of the catheter 93 into the
cerebrospinal fluid (CSF) to provide rapid infusion to all areas of
the brain, or it may be desired to have the outlet of the catheter
93 positioned to deliver medication to one specific location in the
brain or possibly into the bloodstream.
[0170] The operation of the system 910 of FIG. 14 for detecting and
treating a neurological event such as an epileptic seizure is as
follows:
[0171] 1. The event detection sub-system 30 continuously processes
the EEG signals 21A through 21N carried by the wires 17A through
17N from the N electrodes 15A through 15N.
[0172] 2. When an event is detected, the event detection sub-system
30 notifies the central processor 51 via the link 53 that an event
has occurred.
[0173] 3. The central processor 51 signals the drug delivery system
91 via the link 96 to infuse medication through the catheter 93
into the patient's body as a means for stopping a neurological
event.
[0174] 4. The drug delivery system 91 delivers pre-programmed drug
infusion to the desired site.
[0175] 5. The central processor 51 will store EEG and event related
data from X minutes before the event to Y minutes after the event
for later analysis by the patient's physician.
[0176] 6. The central processor 51 may initiate a "buzz" to notify
the patient that an event has occurred by sending a signal via the
link 92 to the buzzer 95.
[0177] Programmable implantable drug delivery systems are described
in some detail in the Fischell patent 4,373,527. It is also
envisioned that both electrical stimulation and drug delivery could
be used together to improve the outcome in the treatment of a
neurological disorder.
[0178] It should also be understood that although the invention
described herein has been described with analog or digital
implementations of various aspects of the invention, the invention
may combine analog and digital elements described herein in
different combinations than as described.
[0179] In addition, although the previous descriptions relate to a
fully implantable system, an externally worn system with implanted
electrodes could function adequately and would allow a plug-in
interface to the data communication sub-system 60 and simple
battery replacement. It is also envisioned that the techniques
described above would work with an external device with electrodes
attached to the outside of the head. External devices would have
great merit in determining if an implantable system would work well
enough to be warranted. An external version with implanted
electrodes could be used to record EEG signals from neurological
events to calculate the optimal programming algorithms and
parameters to be used by a permanently implanted system using the
same set of electrodes.
[0180] It is also envisioned that the EEG recording capabilities of
the present invention could be used without the event detection and
stimulation components to store patient EEG activity for diagnostic
purposes.
[0181] Novel arrangements for the physical placement of the various
parts of a system for the treatment of neurological disorders are
shown in FIGS. 15 to 25 inclusive. Specifically, FIG. 15 shows a
top view of an intracranial system 600 consisting of brain surface
electrodes 601, 602, 603, 604, 605 and 606 connected by wires 611,
612, 613, 614, 615 and 616 respectively which provide an electrical
conducting means to join the electrodes 601 through 606 to a
control module 620. Thus the proximal end of each of the wires 611
through 616 is connected to the control module 620, and the distal
end of each of the wires 611 through 616 is connected to an
electrode. Inside the patient's head 9, these surface electrodes
601-606 are placed between the bottom of the cranium (i.e., inside
the skull) and the top of the dura mater that surrounds the brain.
Thus this is an epidural placement of the surface electrodes.
Although six surface electrodes are shown in FIG. 15, it is
envisioned that as many as 12 or more active electrodes could be
usefully implanted. It is further envisioned that the metal case of
the control module 620 could serve as a common or indifferent
electrode which also could be considered to be at ground potential.
It is further envisioned that the control module might utilize a
case which is non-conducting in which only part of the outer
surface is conducting so as to provide one or more electrodes. Also
shown in FIG. 15 is a deep electrode 601D connected by wire 611D to
the control module 620. It is anticipated that as many as eight
deep electrodes could be used with the intracranial system 600. One
or more deep electrodes might advantageously be placed in the
hippocampus and/or the thalmus or possibly some other portion of
deep brain tissue.
[0182] FIG. 16 is a simplified side view of the human head 9 into
which the intracranial system 600 has been implanted. In this
simplified view, only one brain surface electrode 602 is shown and
one deep electrode 601D. The brain surface electrode 602 is
connected by the insulated wire 612 to control module 620. Also
shown in FIG. 16 is the deep electrode 601D connected by the wire
611D to the control module 620.
[0183] FIGS. 15 and 16 also show that the control module 620 is
located in an anterior portion of the patient's head 9. By an
anterior portion is meant that it is located anterior to the head's
lateral centerline (LCL) that roughly goes through the center of
the ears. Furthermore, the control module 620 cannot be situated on
the anterior-posterior centerline (APCL) because just under the
APCL is the very large sagital sinus vein, and it would be
inadvisable to place the control module 620 at such a location. The
reason for placing the control module 620 in the anterior half of
the patient's cranium is that the middle meningeal artery and its
branches, (which arteries all lie posterior to the LCL) cause
grooves to be formed in the underside of the cranium. Therefore,
that location is also inappropriate for removing the considerable
volume of cranium bone that should be removed for placement of the
control module 620.
[0184] FIGS. 15 and 16 also show that the electrodes are connected
by wires to the control module 620 via holes that are made by
removing bone from the patients cranium. Specifically, the
interconnecting wires 611, 612, 613 and 614 pass respectively
through the holes H1, H2, H3 and H4. It can also be seen in FIG. 15
that the wire 616 passes through the hole H1 and wires 615 and 611D
pass through the hole H4. The reason for this method of sometimes
running most of the wire length between the scalp and the cranium
and at other times running most of the wire length between the
bottom of the cranium and the dura mater has to do with the
movement of the scalp relative to the cranium which occurs on the
anterior portion of the patient's head and also is done to avoid
placing the wires epidurally where the middle meningeal artery and
its branches have made grooves in the interior surface of the
cranium. Specifically, it will be noted that the wires 612 and 613
are placed under the scalp for most of their length because in this
posterior portion of the patient's head the scalp exhibits very
little motion relative to the cranium but the middle meningeal
artery and its branches do cause interior surface grooves in the
cranium in this posterior region of the head. The reverse situation
is seen for the connecting wires 615 and 616. In this case, because
there is considerable motion of the scalp relative to the cranium
in the anterior portion of the patient's head, most of the length
of the wires 615 and 616 is placed epidurally where there are no
grooves in the interior surface of the cranium.
[0185] Indicated by phantom lines in FIG. 15 is the location of an
epileptic focus 630 where an electrode 601 has been placed. As
previously described, it may be advantageous to provide an
electrical short circuit between such an electrode 601 located over
the epileptic focus 630 and the metal case of the control module
620 which acts as an indifferent, common or ground electrode. Also,
responsive stimulation using only the electrode 601 may be
sufficient to abort an epileptic seizure with no other electrode
being actuated.
[0186] FIG. 17 shows the location of the control module 620
connected by wires 631 and 632 to a flat wire input-output coil 635
that is placed in a posterior position on the patient's head along
the APCL.
[0187] FIG. 18 shows a cross section of the patient's cranium along
the APCL showing the cross section of flat wire coil 635 and also
shows a patient initiating device 750 having a case 751 and an
initiating button 752.
[0188] FIG. 19 shows a cross section of the patient's cranium along
the APCL again showing the cross section of the flat wire coil 635
and also the cross section of a cap 636 which includes a flat wire
input-output communication coil 637. The flat wire coils 635 and
637 can act as emitting and receiving devices to provide two-way
communication between the control module 620 and the external
equipment 11.
[0189] The flat wire coil 635 serves several important functions
for the operation of the implanted system 10. A first use is as the
means to communicate by magnetic induction between the external
equipment 11 and the implanted system 600. By "magnetic induction"
is meant that an alternating magnetic field generated by (for
example) the coil 638 generates an electrical current in the coil
635. Such an alternating magnetic field can also be modulated to
provide the wireless two-way communication link 72 of FIG. 2. The
external equipment 11 via the communication coil 637 can be used to
read out telemetry stored in the control module 620 or reprogram
the control module 620 with new software or operational parameters.
Another use of the flat coil 635 is to allow the patient's
initiating device 750 to cause a specific action to occur within
the implanted system 10. For example, the device 750 can be used to
trigger a response from the implanted system 600 that would be
initiated by the patient when he or she feels that some
neurological event was about to occur. For example, when the aura
of a seizure is felt or some visual manifestation of a migraine
headache, the patient would place the device 750 over the site of
the implanted control module and then press the actuate button 752.
The device 750 might have several buttons to initiate different
responses from the implanted system 600. One response that the
patient may wish to have accomplished is to hold in memory the
prior several minutes of recorded EEG data if the patient feels
that data may be important to an understanding of his neurological
condition. Furthermore, the pressing of different buttons could be
used to initiate some different response from the implanted system
600. Specifically, by pressing on the button 752, a coil within the
patient's initiating device 750 can communicate by magnetic
induction with the flat coil 635 to carry out a specific action
such as: (1) hold data stored in the FIFOs to be read out at a
later time, (2) provide a pre-programmed response to stop a
neurological event, (3) turn off the implanted system, and (4)
initiate any other action requested by the patient that has been
pre-programmed by the physician. Another use for the flat coil 635,
as shown in FIG. 19, is to connect the communication coil 637 via
the wire 638 to the charging equipment 639 as required to recharge
a rechargeable battery that would be located in the control module
620. The external equipment 11 could also provide electrical power
to the control module 620 during readout of telemetry or during
reading in of new operational parameters. Powering the control
module 620 from an external source during such times of high power
drains could extend the lifetime of a primary (non-rechargeable)
battery located in the control module 620.
[0190] Although FIG. 17 shows the flat coil 635 located remotely
from the control module 620, such a coil could also be placed on
the surface of or interior to the control module 620. Remote
placement has the advantage that the high frequency and intense
alternating magnetic field required for communication or recharging
would not be placed onto the electronics portion of the control
module 620 thus avoiding interference with the operation of the
system 600. The coupling by magnetic induction of the coil 635 with
either the device 750 or the communication coil 637can provide the
wireless communication link 72 of FIG. 2. It is envisioned that any
of the two-way communication capabilities described herein could be
implemented with either the electromagnetic induction structures as
shown in FIGS. 17, 18 and 19 or by the radio frequency (RF)
components shown in FIG. 11.
[0191] FIG. 20 is a top view of a thin-walled metal shell 621 which
acts as a base for the control module 620. FIG. 21 is a cross
section of the control module 620 and also shows the cross section
of the shell 621 as indicated by the section 21-21 in FIG. 20.
FIGS. 20 and 21 show that the shell 621 has a flange 622 and four
holes through which are inserted bone screws 623 that attach the
shell 621 to the bony structure of the cranium. Also shown in FIG.
20 and 21 are input wires (of which only wire 611 is indicated)
that enter the insulating strain relief structure 640. On the
interior of the shell 621 are male connecting pins 641 which are
designed to mate with a female receptacle which forms part of the
electronics module 626 that is shown in FIG. 21. The electronics
module 626 contains most if not all of the electronic circuitry
that is contained within the control module 620. Also shown in FIG.
21 is the battery 625 which has a top plate 624 that extends over
the flange 622 of the shell 621. An 0-ring 627 is used to provide a
fluid seal to prevent body fluids from entering the control module
620. A silicone rubber adhesive or small metal screws could be used
to join the top plate 624 to the flange 622 of the shell 621. The
shell 621, battery 625, and electronics module 626 constitute the
three major parts of the control module 620.
[0192] The control module 620, is designed for easy implantation
within a space in the cranium where the bone has been removed. The
thickness of the cranium at the site of the implantation would be
approximately 10 mm. Therefore, the thickness of the control module
620 would be approximately the same 10 mm with a diameter of
approximately 40 mm. To implant the control module 620, the hair
would be shaved over the implantation site, an incision would be
made in the scalp, and the bone would be removed to make room for
the control module 620. In a similar manner, holes such as H1-H4
inclusive would be made in the cranium for the pass-through of
wires connecting to the brain electrodes.
[0193] Although FIG. 21 shows the electronics module 626 located
beneath the battery 625, it also envisioned that those positions
could be reversed if such positioning offered a more advantageous
construction. In either case, either the battery 625 or the
electronics module 626 could be readily replaced through a simple
incision in the scalp over the site of the implanted control module
620 after the hair has been removed from the incision site.
[0194] FIG. 22 illustrates an alternative embodiment of the
invention in which the system 700 for the treatment of neurological
disorders utilizes a control module 720 that is located in the
patient's chest. The system 700 uses epidural electrodes 701, 702
and 703 and a deep electrode 701D; the electrodes being joined by
connecting wires 711, 712, 713 and 711D, respectively, through a
wire cable 710 to the control module 720. The electrode 701 is
shown placed at an epileptic focus 730. This system can be used in
exactly the same manner as previously described for the system 10
that had a control module 20 that was placed within the
cranium.
[0195] FIG. 23 illustrates another embodiment of the invention
which utilizes a control module placed between the patient's scalp
and cranium and a remotely located implantable sensor/actuator
device 850 located within the patient's body but not in the
patient's head. The system 800 could operate in one of two modes.
In the first mode, the sensor/actuator device 850 would operate as
a sensor for sensing some physiological condition such as an
elevated blood pressure or an electrical signal from a nerve or
muscle indicating the presence of pain. The active electrode 854 is
connected by the wire 851 to the sensor/actuator device 850 using
the metal case of the sensor/actuator device 850 as an indifferent
electrode. An electrical signal in the frequency range 1 to 500 kHz
emitted from the electrode 854 could be used to communicate with
the control module 820, thus providing a signaling means to the
control module 820 from the remote sensor/actuator device 850. Of
course, such signaling means can also be provided from the control
module 820 to the sensor/actuator device 850. The electrical signal
from the sensor/actuator device 850 would be detected between the
active electrode 801 and an indifferent electrode that could be the
metal case of control module 820 or it could be a separate
electrode. The active electrode 801 is connected to the control
module 820 by the connecting wire 811. It should be noted that in
FIG. 23, the electrode 801 is placed epidurally at the bottom of
the hole H8. This can be a comparatively simple way to place an
epidural electrode.
[0196] Having received a signal from the sensor/actuator device 850
acting as a sensor, the control module 820 would send a signal via
the wire 812 to electrode 802 to act on that portion of the brain
that would result in a treatment of the physiological condition
that caused the sensor/actuator device 850 to communicate with the
control module 820. Thus, for example, if the electrode 854 detects
a pain signal from a nerve in the back, the electrode 802 could be
used to turn off a certain region of the brain so that the patient
would not perceive that pain.
[0197] A second mode of operation for the system 800 would be when
the intracranial portion of the system 800 is used for sensing an
adverse physiological condition, and the sensor/actuator device 850
is used as an actuator to carry out some treatment at a remote
location to ameliorate that adverse physiological condition. In
this mode, the electrode 802 would sense the adverse condition and
send an alternating electrical signal out from electrode 801 to
carry out some treatment at a remote location within the body. The
electrode 854 would receive that signal and could cause the
sensor/actuator device 850 to carry out a pre-programmed treatment.
For example, if a migraine headache is perceived by the control
module 820, the sensor/actuator device 850 could be instructed to
release medication via the catheter 853 into the cerebrospinal
fluid (the CSF) to relieve that headache. Or a Parkinson's disease
tremor might be detected and the neurotransmitter epinephrine would
be appropriately released into the CSF to relieve that tremor. In
another example, if the patient thought about moving a certain
muscle that had been made inoperative due to interrupted nerve
conduction, that muscle could be activated by the electrode 856
which is connected by the wire 852 to the sensor/actuator device
850.
[0198] It should be understood that the communication signal means
between the control module 820 and the sensor/actuator device 850
could be modulated by any one of several well known techniques
(such as AM, FM, phase modulation, etc.) in order to carry out
proportional responses based upon the sensing signal received by
the electrode 802 and processed by the control module 820. It
should also be understood that communication between the control
module 820 and the remote sensor/actuator device 850 could be
accomplished by acoustic (e.g. ultrasonic) vibrations from a buzzer
at either location to a microphone at the receiving end of the
transmission or by any suitable electromagnetic communication
means. Of course it is also understood that a multiplicity of
electrodes could be used with either the control module 820 or the
sensor/actuator device 850, and that both the control module 820
and the remote sensor/actuator device 850 might together produce
the response to a detected event.
[0199] It is further envisioned the signaling means between the
control module 820 and the remote sensor/actuator device 850 may be
in the form of either analog or digital signals.
[0200] FIG. 23 also illustrates how a buzzer 95 connected by the
wires 92 to a control module 820 could be used as part of the means
for stopping a neurological event such as an epileptic seizure.
Since the buzzer could be located in close proximity to the ear, if
it produces an acoustic output when an epileptic seizure is
detected by the control module 820, that acoustic input into the
brain can stop the epileptic seizure. Furthermore, a hearing aid
type of acoustic output device 895 placed in the ear could have an
acoustic output of a particular intensity and pitch that could turn
off the seizure. The operation of either the buzzer 95 or the
acoustic output device 895 would be automatic, i.e., when a seizure
precursor is detected, an acoustic input signal would be applied
automatically. The device 895 could be actuated by receiving a
signal from the buzzer 95.
[0201] FIG. 23 also shows a visual light source 896 that could be a
light emitting diode in eyeglasses worn by the patient or a special
flashlight type of device. Either device could be used with a
particular wavelength of light and rate of flashing on and off so
as to provide a visual input that could act as a means for stopping
an epileptic seizure. Although the light source 896 could be
automatic if it were on a pair of eyeglasses, if a flashlight type
of device is used, the visual input would be manually applied.
[0202] Also shown in FIG. 23 is a sensory actuator 897 which can
apply electrical stimulation to electrodes 898 through wires 899 to
the patient's skin. The sensory actuator 897 might also produce
mechanical vibrations applied directly to the patient's skin.
[0203] FIG. 24 shows an alternative embodiment of the invention,
which uses a multiple pin, pyrolytic carbon receptacle 911 placed
through the patient's scalp which provides a multiplicity of
electrical connections for the control module 920. Specifically,
the system 900 has a control module 920 that is electrically
connected to the receptacle 911 by means of the wire cable 922. The
mating plug 912 is connected by the cable 913 to provide two-way
communication via electrical wires between the control module 920
and the external equipment 11. The plug 912 and cable 913 can also
be used with the charging equipment 914 to recharge a rechargeable
battery (not shown) located in the control module 920.
[0204] Also shown in FIG. 24 are other alternative means for
providing two-way communication between the control module 920 and
the external equipment 11. Specifically, FIG. 24 shows an acoustic
(ultrasonic) transducer 931 mounted on the control module 920 that
can communicate with the externally located transducer 932 which is
in two-way communication with the external equipment 11 through the
wire cable 933. In a similar manner, an infrared emitter/receiver
941 can send an infrared signal through the patient's scalp to an
infrared emitter/receiver 943 that is connected by the wire cable
943 to the external equipment 11.
[0205] By any of these methods, either direct electrical
connection, or acoustic or infrared two-way communication the
equivalent function of element 72 in FIG. 2 can be accomplished. It
has already been established that two-way communication 72 can also
be accomplished by a variety of electromagnetic means including an
alternating magnetic field or by radio frequency communication.
[0206] FIG. 24 also shows other locations for electrodes that are
to be placed in close proximity to the brain. Specifically, FIG. 24
shows an electrode 950 mounted on the outer surface of the scalp
that is connected by the cable wire 951 to the control module 920.
Such an external electrode 950 could also be used with an
externally placed control module (not shown). Additionally,
electrodes such as the electrode 960 could be placed between the
patient's scalp and cranium and would be connected by the wire
cable 961 to the control module 920. Furthermore, electrodes such
as the electrode 950 could be placed between the dura mater and the
arachnoid and would be connected via the wire cable 971 to the
control module 920.
[0207] It should be noted that any of the electrodes described
herein that are in the general proximity of the brain either inside
or on top of the patient's head or deep within the patient's brain
can all be considered to be "brain electrodes."
[0208] FIG. 25 illustrates a system 980 for the treatment of
neurological disorders that uses an external control module 990
with either internal or external means for stopping a neurological
event. Specifically, the scalp mounted electrode 994 connected by
the wire 996 to the control module 990 could be used to detect a
neurological event. Of course one could use a multiplicity of such
scalp-mounted electrodes. Once a neurological event has been
detected, the control module 990 could actuate an acoustic input
device 895, or a visual light input device 986 or an actuator 897
for other sensory inputs. Thus, such a system 980 envisions a
control module 990 mounted external to the patient that uses
external remote actuators that can provide acoustic, visual or
other sensory inputs that could stop an epileptic seizure.
[0209] Furthermore, the system 980 envisions the use of the
externally mounted control module 990 with electrodes mounted in
close proximity to the brain or actually within the brain (i.e.
"brain electrodes"). Specifically, the electrodes 801 and 802 could
be mounted on the dura mater and a deep electrode 801D could be
placed within the brain itself. The wires 811, 812 and 811D could
be connected to receptacle 982 that is mated to the plug 984 that
connects by the wire 992 to the control module 990. The electrodes
801, 802 and 801D could be used either for sensing a neurological
event or for providing an electrical stimulation to stop such a
neurological event.
[0210] In FIG. 25, the remote sensor/actuator device 850 can be
used as part of the means for stopping a neurological event by
applying an electrical stimulus to one or two vagus nerves by means
of the electrodes 854 and/or 856. This could also be accomplished
using the system shown in FIG. 23, i.e., with any control module
820 (or 20) that is implanted beneath the scalp. In FIG. 25 the
catheter 853 can be used to apply medication as part of the means
for stopping a neurological event. The sensor/actuator device 850
can be triggered to stop the neurological event by means of a
signal originating from the externally mounted control module
990.
[0211] Also shown in FIG. 25 is an external remote actuator 897
which can apply electrical stimulation to electrodes 898 through
wires 899 to the patient's skin. The actuator 897 might also
produce mechanical vibrations applied directly to the patient's
skin as another form of sensory input.
[0212] Additional objects and advantages of the present invention
will become apparent to those skilled in the art to which this
invention relates from the subsequent description of the preferred
embodiments and the appended claims, taken in conjunction with the
accompanying drawings.
* * * * *