U.S. patent application number 10/963305 was filed with the patent office on 2005-03-03 for pelvic disorder treatment device.
This patent application is currently assigned to BIOCONTROL MEDICAL LTD.. Invention is credited to Cohen, Ehud, Gross, Yossi, Nissenkorn, Israel.
Application Number | 20050049648 10/963305 |
Document ID | / |
Family ID | 25543168 |
Filed Date | 2005-03-03 |
United States Patent
Application |
20050049648 |
Kind Code |
A1 |
Cohen, Ehud ; et
al. |
March 3, 2005 |
Pelvic disorder treatment device
Abstract
A device for treating a medical condition is provided, and a
surgical procedure for implanting the device is disclosed. The
device includes a sensor, which is adapted to generate a signal
responsive to a state of a patient, and at least one electrode,
which is adapted to be coupled to a pelvic site of the patient. A
control unit is adapted to receive the signal, to analyze the
signal so as to distinguish between an imminent stress incontinence
event and an imminent urge event, and, responsive to analyzing the
signal, to apply an electrical waveform to the at least one
electrode. In various configurations, the device may be used
alternatively or additionally to treat fecal incontinence,
interstitial cystitis, chronic pelvic pain, or urine retention.
Inventors: |
Cohen, Ehud; (Ganei Tikva,
IL) ; Gross, Yossi; (Moshav Mazor, IL) ;
Nissenkorn, Israel; (Ramat Aviv, IL) |
Correspondence
Address: |
Ladas & Parry
26 West 61st Street
New York
NY
10023
US
|
Assignee: |
BIOCONTROL MEDICAL LTD.
|
Family ID: |
25543168 |
Appl. No.: |
10/963305 |
Filed: |
October 12, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10963305 |
Oct 12, 2004 |
|
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|
09996668 |
Nov 29, 2001 |
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Current U.S.
Class: |
607/41 |
Current CPC
Class: |
A61B 5/227 20130101;
A61B 5/205 20130101; A61B 5/204 20130101; A61B 5/0031 20130101;
A61B 5/145 20130101; A61N 1/36007 20130101; A61B 5/389 20210101;
A61B 8/4472 20130101; A61B 2562/0219 20130101; A61B 8/12 20130101;
A61B 5/4047 20130101; A61B 5/0215 20130101; A61B 2560/0209
20130101; A61B 5/202 20130101; A61B 5/6874 20130101 |
Class at
Publication: |
607/041 |
International
Class: |
A61N 001/18 |
Claims
1. A device, comprising: a sensor, which is adapted to generate a
signal responsive to a state of a patient; at least one electrode,
which is adapted to be coupled to a pelvic site of the patient; and
a control unit, which is adapted to receive the signal, to analyze
the signal so as to distinguish between an imminent stress
incontinence event and an imminent urge event, and, responsive to
analyzing the signal, to apply an electrical waveform to the at
least one electrode.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to electronic
medical devices, and specifically to devices to relieve problems
associated with urinary incontinence and other pelvic
disorders.
BACKGROUND OF THE INVENTION
[0002] Urinary incontinence affects millions of people, causing
discomfort and embarrassment, sometimes to the point of social
isolation. In the United States, recent studies have shown that as
many as 25 million persons, of whom approximately 85% are women,
are affected by bladder control problems. Incontinence occurs in
children and young adults, but the largest number affected are the
elderly.
[0003] There are several major forms of incontinence:
[0004] Stress incontinence is an involuntary loss of urine while
doing physical activities which put pressure on the abdomen. These
activities include exercise, coughing, sneezing, laughing, lifting,
or any body movement which puts pressure on the bladder. Stress
incontinence is typically associated with either or both of the
following anatomical conditions:
[0005] Urethral hypermobility--Weakness of or injury to pelvic
floor muscles causes the bladder to descend during abdominal
straining or pressure, allowing urine to leak out of the bladder.
This is the more common source of stress incontinence.
[0006] Intrinsic sphincter deficiency--In this condition, the
urethral musculature is unable to completely close the urethra or
keep it closed during stress.
[0007] Urge incontinence is the sudden urgent need to pass urine,
and is caused by a sudden bladder contraction that cannot be
consciously inhibited. This type of incontinence is not uncommon
among healthy people, and may be linked to disorders such as
infections that produce muscle spasms in the bladder or urethra.
Urge incontinence may also result from illnesses that affect the
central nervous system.
[0008] Overflow incontinence refers to leakage of urine that occurs
when the quantity of urine exceeds the bladder's holding capacity,
typically as a result of a blockage in the lower urinary tract.
[0009] Reflex incontinence is the loss of urine when the person is
unaware of the need to urinate. This condition may result from
nerve dysfunction, or from a leak in the bladder, urethra, or
ureter.
[0010] Of the major forms of incontinence listed above, the two
most common are stress and urge. "Mixed incontinence" is a term
used to describe the common phenomenon of the presence of stress
and urge incontinence in the same patient.
[0011] A large variety of products and treatment methods are
available for care of incontinence. Most patients suffering from
mild to moderate incontinence use diapers or disposable absorbent
pads. These products are not sufficiently absorbent to be effective
in severe cases, are uncomfortable to wear, and can cause skin
irritation as well as unpleasant odors. Other non-surgical products
for controlling incontinence include urethral inserts (or plugs),
externally worn adhesive patches, and drugs.
[0012] Exercise and behavioral training are also effective in some
cases in rehabilitating pelvic muscles and thus reducing or
resolving incontinence. Patients are taught to perform Kegel
exercises to strengthen their pelvic muscles, which may be combined
with electrical stimulation of the pelvic floor. Electromyographic
biofeedback may also be provided to give the patients an indication
as to the effectiveness of their muscular exertions. But retraining
muscles is not possible or fully effective for most patients,
particularly when there may be neurological damage or when other
pathologies may be involved.
[0013] Medtronic Neurological, of Columbia Heights, Minn., produces
a device known as Interstim, for treatment of urge incontinence.
Interstim uses an implantable pulse generator, which is surgically
implanted in the lower abdomen and wired to nerves near the sacrum
(the bone at the base of the spine) in a major surgical
procedure--sometimes six hours under general anesthesia. Electrical
impulses are then transmitted continuously to a sacral nerve that
controls urinary voiding. The continuous electrical stimulation of
the nerve has been found to control urge incontinence in some
patients.
[0014] Various surgical procedures have been developed for bladder
neck suspension, primarily to control urethral hypermobility by
elevating the bladder neck and urethra. These procedures typically
use bone anchors and sutures or slings to support the bladder neck.
The success rates for bladder neck suspension surgery in
controlling urinary leakage are typically approximately 60%-80%,
depending on the patient's condition, the surgeon's skill, and the
procedure which is used. The disadvantages of this surgical
technique are its high cost, the need for hospitalization and long
recovery period, and the frequency of complications.
[0015] For serious cases of intrinsic sphincter deficiency,
artificial urinary sphincters have been developed. For example, the
AMS 800 urinary sphincter, produced by American Medical Systems
Inc., of Minnetonka, Minn., includes a periurethral inflatable
cuff, which is used to overcome urinary incontinence when the
function of the natural sphincter is impaired. The cuff is coupled
to a manually-operated pump and a pressure regulator chamber, which
are implanted in a patient's body together with the cuff. The cuff
is maintained at a constant pressure of 60-80 cm of water, which is
generally higher than the bladder pressure. To urinate, the patient
releases the pressure in the cuff. Aspects of this system are
described in U.S. Pat. No. 4,222,377 to Burton, which is
incorporated herein by reference.
[0016] This artificial sphincter has several shortcomings, however.
The constant concentric pressure that the periurethral cuff exerts
on the urethra can result in impaired blood supply to tissue in the
area, leading to tissue atrophy, urethral erosion and infection.
Furthermore, the constant pressure in the cuff is not always
sufficient to overcome transient increases in bladder pressure that
may result from straining, coughing, laughing or contraction of the
detrusor muscle. In such cases, urine leakage may result.
[0017] U.S. Pat. Nos. 4,571,749 and 4,731,083 to Fischell, which
are incorporated herein by reference, describe an artificial
sphincter device whose pressure can vary in response to changes in
abdominal or intravesical (bladder) pressure. The device includes a
periurethral cuff, subdermic pump, pressure regulator, and
hydraulic pressure sensor.
[0018] U.S. Pat. No. 3,628,538 to Vincent et al., which is
incorporated herein by reference, describes apparatus for
stimulating a muscle based on an electromyographic (EMG) signal
sensed in the muscle. If the signal is greater than a predetermined
threshold value, a stimulator circuit applies a voltage to
electrodes adjacent to the muscle. The apparatus is said to be
particularly useful in overcoming incontinence.
[0019] U.S. Pat. No. 6,135,945 to Sultan, which is incorporated
herein by reference, describes apparatus for preventing
uncontrolled discharge of urine from a patient's urethra. The
apparatus includes an implantable pressure sensor for sensing
intra-abdominal pressure, which generates a pressure signal in
response to the sensed pressure. An actuating device is coupled to
the pressure sensor, and generates an electrical signal in response
to the pressure signal. A controller is coupled to the actuating
device, and is configured to selectively compress the patient's
urethra and thereby prevent incontinence.
[0020] Various types of electrodes have been proposed for applying
electrical stimulation to pelvic muscles so as to prevent unwanted
urine flow. For example, U.S. Pat. No. 5,562,717 to Tippey et al.
describes electrodes that are placed on the body surface, typically
in the areas of the perineum and the sacrum, and are electrically
actuated to control incontinence. U.S. Pat. No. 4,785,828 to Maurer
describes a vaginal plug having electrodes on an outer surface
thereof. A pulse generator in the plug applies electrical pulses to
the electrodes so as to constrict the patient's pelvic muscles and
prevent urine flow. U.S. Pat. No. 4,153,059 to Fravel et al.
describes an intra-anal electrode, to which repetitive electrical
pulses are applied in order to control urinary incontinence. U.S.
Pat. No. 4,106,511 to Erlandsson describes an electrical stimulator
in the form of a plug for insertion into the vagina or the anus.
U.S. Pat. No. 3,866,613 to Kenny et al. describes a pessary ring
having two electrodes thereon, which are energized to control
incontinence. U.S. Pat. No. 4,406,288 to Horwinski et al. describes
apparatus for conditioning the pelvic floor musculature to reduce
bladder contractility and relax the bladder, so as to prevent
involuntary urinary loss. All of the above-mentioned patents are
incorporated herein by reference.
[0021] U.S. Pat. No. 4,580,578 to Barson, which is incorporated
herein by reference, describes a device for stimulating the
sphincter muscles controlling the bladder. A supporting body is
fitted into the patient's vulva between the labia, so that two
electrodes attached to the supporting body contact the epidermal
surface on either side of the external urethral orifice. Electrical
impulses are applied to the electrodes to stimulate the region of
the sphincter.
[0022] U.S. Pat. No. 4,607,639 to Tanagho et al., which is
incorporated herein by reference, describes a method for
controlling bladder function by nerve stimulation, typically of a
sacral nerve. The anatomical location of at least one nerve
controlling the muscles for the bladder and/or its sphincter is
identified, and an electrode is placed on the nerve to selectively
stimulate the nerve for continence and evacuation purposes.
[0023] U.S. Pat. No. 4,739,764 to Lue et al., which is incorporated
herein by reference, describes a system for electrical stimulation
of nerves in order to treat urinary incontinence, fecal
incontinence, interstitial cystitis, and other pelvic pain
syndromes.
[0024] U.S. Pat. No. 6,240,315 to Mo et al., which is incorporated
herein by reference, describes incontinence treatment apparatus
which includes a module for evaluating a recorded EMG signal.
[0025] U.S. Pat. No. 5,484,445 to Knuth, which is incorporated
herein by reference, describes a system for anchoring a lead to the
sacrum for purposes of long-term stimulation, typically for
treatment of incontinence.
[0026] U.S. Pat. Nos. 5,927,282 and 6,131,575 to Lenker et al.,
which are incorporated herein by reference, describe removable
external closures for the urethra as means for relieving or
mitigating incontinence problems.
[0027] U.S. Pat. No. 6,002,964 to Feler et al., which is
incorporated herein by reference, describe a method for managing
chronic pelvic pain. The method includes techniques for positioning
one or more stimulation leads within or about the sacrum to enable
electrical energy to be applied to spinal nervous tissue, including
nerve roots, in order to inhibit the transmission of pain
signals.
[0028] An article by Fall et al., entitled, "Electrical stimulation
in interstitial cystitis," Journal of Urology, 123(2), pp. 192-195,
February, 1980, which is incorporated herein by reference,
describes a study in which fourteen women with chronic interstitial
cystitis were treated with long-term intravaginal or transcutaneous
nerve stimulation. Clinical and urodynamic evaluations were
performed after 6 months to 2 years. Improvement was not immediate,
but required a considerable period of continuous, daily use of
electrical stimulation.
[0029] An article by Zermann et al., entitled, "Sacral nerve
stimulation for pain relief in interstitial cystitis," Urol. Int.,
65(2), pp. 120-121, 2000, which is incorporated herein by
reference, describes a case in which a 60-year-old woman was
treated for severe interstitial cystitis pain using sacral nerve
stimulation.
[0030] An article by Chai et al., entitled, "Percutaneous sacral
third nerve root neurostimulation improves symptoms and normalizes
urinary HB-EGF levels and antiproliferative activity in patients
with interstitial cystitits," Urology, 55(5), pp. 643-646, May,
2000, which is incorporated herein by reference, notes: "A highly
effective treatment for interstitial cystitis (IC) remains elusive.
. . . Results suggest that permanent S3 PNS may be beneficial in
treating IC."
[0031] An article by Caraballo et al., entitled, "Sacral nerve
stimulation as a treatment for urge incontinence and associated
pelvic floor disorders at a pelvic floor center: a follow-up
study," Urology, 57(6 Suppl 1), p. 121, June, 2001, which is
incorporated herein by reference, describes and presents the
results of an additional study in which sacral nerve stimulation
was applied in an effort to treat urinary incontinence.
[0032] PCT Patent Publication WO 00/19939, entitled, "Control of
urge incontinence," which is assigned to the assignee of the
present patent application and incorporated herein by reference,
describes a device for treatment of urinary urge incontinence, in
which imminent urge incontinence is sensed, and a pelvic nerve or
muscle is stimulated to inhibit the flow.
[0033] PCT Patent Publication WO 00/19940, entitled, "Incontinence
treatment device," which is assigned to the assignee of the present
patent application and incorporated herein by reference, describes
a device for treating urinary stress incontinence, in which
imminent involuntary urine flow is sensed, and a pelvic nerve or
muscle is stimulated to inhibit the flow.
[0034] A book entitled Urinary Incontinence, edited by P.
O'Donnell, Mosby Publishers, 1997, which is incorporated herein by
reference, describes clinical aspects relating to the diagnosis and
treatment of urinary incontinence.
SUMMARY OF THE INVENTION
[0035] It is an object of some aspects of the present invention to
provide devices and methods for treating mixed incontinence.
[0036] It is a further object of some aspects of the present
invention to provide improved devices and methods for relieving
pelvic pain.
[0037] It is yet a further object of some aspects of the present
invention to provide improved devices and methods for treating
fecal incontinence.
[0038] It is yet a further object of some aspects of the present
invention to provide improved devices and methods for treating
urine retention.
[0039] It is still a further object of some aspects of the present
invention to provide improved methods for implanting pelvic
electrical apparatus.
[0040] In preferred embodiments of the present invention, a device
for treatment of both urinary stress incontinence and urge
incontinence comprises a control unit, one or more electrodes
coupled to the control unit, and one or more sensors, also coupled
to the control unit. The electrodes are preferably implanted in the
pelvic region of a patient so as to be in electrical contact with
one or more of the muscles or nerves that are used in regulating
urine flow from the bladder. The control unit is preferably
implanted under the skin of the abdomen or genital region, and
receives signals from the electrodes and/or from the sensors.
Motion, pressure and/or electromyographic (EMG) signals conveyed by
the electrodes or sensors are analyzed by the control unit, as
described hereinbelow, in order to distinguish between signals
indicative of urge incontinence and those indicative of stress
incontinence. When the control unit determines that the signals are
indicative of impending urge incontinence, it drives the electrodes
to apply a signal having parameters configured to treat urge
incontinence. When, however, the control unit determines that the
signals are indicative of stress incontinence, it drives the
electrodes to apply a signal having parameters that are configured
to treat stress incontinence. As appropriate, the control unit may
also configure the current applied by the electrodes so as to treat
other disorders, such as fecal incontinence, interstitial cystitis,
urine retention, or other sources of pelvic dysfunction, pain or
discomfort.
[0041] It is to be appreciated that, in the context of the present
patent application and in the claims, treatments described for
inhibiting "imminent" conditions such as an event of stress
incontinence which is expected to occur, may also be applied to
inhibit a presently-occurring condition, such as involuntary
voiding due to stress incontinence.
[0042] In addition, it is to be appreciated that although some
preferred embodiments of the present invention are described herein
with respect to treating urge incontinence, the scope of the
present invention includes treating other urge "events" as well.
For example, urge events such as urge frequency (the excessively
frequent sensation of very imminent voiding, in patients who do not
necessarily experience incontinence following such sensations) or
neurogenic bladder conditions are preferably treated using
identical protocols as those described herein for the treatment of
urge incontinence, or protocols analogous to those described herein
for the treatment of urge incontinence, mutatis mutandis.
[0043] Preferably, the control unit is programmed to distinguish
between signals indicative of possible incontinence and other
signals that do not warrant stimulation of the muscles. In
particular, the control unit is preferably programmed to recognize
signal patterns indicative of normal voiding, and, consequently,
does not stimulate the muscles when such patterns occur.
[0044] Typically, devices in accordance with preferred embodiments
of the present invention actuate the electrodes to treat urge or
stress incontinence only when physiological or other signals
indicate that such treatment is needed. At other times, stimulation
is generally not applied. Implantation of the device provides
reliable, typically long-term control of muscle function, and
relieves incontinence or other pelvic disorders in a manner that is
unobtrusive and minimizes inconvenience and discomfort of the
patient. By contrast, many prior art electrical devices for
treating pelvic disorders are not implanted or intended for
long-term use, but are instead intended for temporary use, e.g., to
train pelvic muscles via a device incorporated in a vaginal plug.
These prior art devices are typically removed after a relatively
short treatment period.
[0045] Numerous benefits are obtained, according to these
embodiments, by actuating the electrodes only "on-demand," i.e.,
only when possible imminent stress or urge incontinence is
detected. For example, muscle fatigue and nerve irritation--both
phenomena being associated with continuous excitation--are
typically reduced or eliminated according to these embodiments.
Accordingly, power consumption is reduced, and battery life is
thereby increased.
[0046] Preferably, the electrodes are implanted so as to stimulate
muscles of the pelvic floor. Alternatively or additionally, one or
more of the electrodes may be implanted in or adjacent to the
detrusor muscle or in a position suitable for stimulating a nerve,
such as the sacral nerve, as described in the above-mentioned U.S.
Pat. No. 4,607,639, for example, or in one or more of the other
references cited in the Background section of the present patent
application.
[0047] In some preferred embodiments of the present invention, the
one or more electrodes comprise a single electrode, which both
receives the EMG signals and applies the stimulation waveform.
Alternatively, separate sensing and stimulation electrodes may be
used.
[0048] In some preferred embodiments of the present invention, the
sensors comprise one or more mechanical sensors, such as pressure,
force, motion or acceleration sensors, or an ultrasound transducer,
which are preferably implanted on, in or in the vicinity of the
bladder. These sensors preferably generate signals responsive to
motion, to intravesical or abdominal pressure, or to urine volume
in the bladder, and are thus indicative of possible imminent
incontinence. The control unit processes the signals from the
sensors in order to determine whether and what type of electrical
stimulation should be applied.
[0049] In a preferred embodiment of the present invention, the
patient herself instructs the control unit to initiate stimulation
of the muscles. For example, the patient may input the instruction
to the control unit by voluntarily tightening her abdominal
muscles, which in turn causes measurable increases in abdominal
pressure. Typically, this is done when the patient senses imminent
urge incontinence. The control unit distinguishes the voluntary
contraction from other sources of pressure changes responsive to
the rate of change of the measured pressure. Alternatively or
additionally, the control unit comprises an external input unit,
such as a keypad, through which the patient enters instructions.
For some applications, the patient is further enabled to indicate
to the control unit that she feels imminent stress incontinence,
e.g., shortly prior to sneezing.
[0050] In a preferred embodiment of the present invention, the
processor is programmable after implantation of the device, most
preferably by means of a wireless communications link, so that the
strength and shape of the stimulation waveform and the response of
the device to the electromyographic and/or other physiological
signals can be adjusted in response to the patient's clinical
characteristics and experience with the device. The wireless link
can preferably also be used by the patient to turn the device on or
off. Such methods of signal processing, programming and control, as
well as other useful methods and apparatus, are described in U.S.
patent application Ser. No. 09/413,272, entitled "Incontinence
Treatment Device," which is assigned to the assignee of the present
patent application and incorporated herein by reference.
[0051] There is therefore provided, in accordance with a preferred
embodiment of the present invention, a device, including:
[0052] a sensor, which is adapted to generate a signal responsive
to a state of a patient;
[0053] at least one electrode, which is adapted to be coupled to a
pelvic site of the patient; and
[0054] a control unit, which is adapted to receive the signal, to
analyze the signal so as to distinguish between an imminent stress
incontinence event and an imminent urge event, and, responsive to
analyzing the signal, to apply an electrical waveform to the at
least one electrode.
[0055] In a preferred embodiment, the at least one electrode
includes a single electrode adapted to be coupled to the pelvic
site, wherein the control unit is adapted to apply a first waveform
to the single electrode responsive to determining that a stress
incontinence event is imminent, and wherein the control unit is
adapted to apply to the single electrode a second waveform,
different from the first waveform, responsive to determining that
an urge event is imminent.
[0056] Typically, the control unit is adapted to analyze the signal
so as to distinguish between the imminent stress incontinence event
and an imminent urge incontinence event. Alternatively or
additionally, the control unit is adapted to analyze the signal so
as to distinguish between the imminent stress incontinence event
and an urge-frequency event.
[0057] In a preferred embodiment, the control unit is adapted to
receive an input from the patient and to apply the waveform
responsive to the input.
[0058] For some applications, the at least one electrode is adapted
to be implanted so as to stimulate a nerve in the pelvic region of
the patient. Alternatively or additionally, the at least one
electrode is adapted to be implanted in contact with a pelvic
muscle of the patient.
[0059] In a preferred embodiment, the at least one electrode
includes:
[0060] a first electrode, adapted to be coupled to a first pelvic
site; and
[0061] a second electrode, adapted to be coupled to a second pelvic
site,
[0062] wherein the control unit is adapted to apply a first
waveform to the first electrode responsive to analyzing the signal
and determining that a stress incontinence event is imminent, and
wherein the control unit is adapted to apply to the second
electrode a second waveform, different from the first waveform,
responsive to determining that an urge event is imminent.
[0063] In this case, the first electrode is often adapted to be
coupled to a pelvic muscle of the patient, while the second
electrode is adapted to be coupled to a sacral nerve of the
patient.
[0064] Preferably, the control unit is adapted to configure the
waveform so as to stimulate a pelvic muscle to contract so as to
inhibit involuntary urine flow through the patient's urethra.
Typically, the control unit is adapted to configure the waveform so
as to stimulate the pelvic muscle to contract responsive to
analyzing the signal and determining that a stress incontinence
event is imminent. Moreover, the control unit is preferably adapted
to configure the waveform to have (a) a frequency component between
about 40 and 50 Hz, (b) an amplitude between about 3 and 9 V, (c) a
series of pulses having widths between about 0.05 and 1 ms, and/or
a duration between about 0.2 and 1 second, responsive to
determining that a stress incontinence event is imminent.
[0065] In a preferred embodiment, the control unit is adapted to
configure the waveform so as to induce relaxation of a bladder
muscle of the patient. Typically, the control unit is adapted to
configure the waveform so as to induce the relaxation of the
bladder muscle responsive to analyzing the signal and determining
that an urge event is imminent. In this case, the control unit is
preferably adapted to configure the waveform to have (a) a
frequency component between about 5 and 15 Hz, (b) a duration less
than about 10 minutes, (c) an amplitude between about 0.5 and 5 V,
and/or (d) a series of pulses having widths between about 0.05 and
1 ms, responsive to determining that an urge event is imminent. For
some applications, the control unit is adapted to configure the
waveform to include a rise time lasting between about 1 second and
1 minute prior to attaining a designated waveform application
voltage, responsive to determining that an urge event is imminent.
Alternatively or additionally, the control unit is adapted to
configure the waveform to include a decay time lasting between
about 1 second and 1 minute prior to returning to a baseline
voltage, responsive to determining that an urge event is
imminent.
[0066] In a preferred embodiment, the control unit is adapted to
configure the waveform to have a duty cycle between about 5% and
15%, responsive to determining that an urge event is imminent.
[0067] For some applications, the sensor includes a sensing
electrode adapted to sense electrical activity of a bladder muscle
of the patient. Preferably, but not necessarily, the at least one
electrode includes the sensing electrode, and the control unit is
adapted to apply the waveform to the sensing electrode responsive
to analyzing the signal.
[0068] Typically, the sensor includes a pressure sensor, and the
control unit is adapted to analyze a rate of change of the received
signal, to identify the imminent stress incontinence event
responsive to a relatively high rate of change of the received
signal, and to identify the imminent urge event responsive to a
relatively low rate of change of the received signal. In a
preferred embodiment, the sensor is adapted to be implanted at an
abdominal site of the patient, and the sensor is adapted to
generate the signal with a relatively low rate of change responsive
to voluntary contraction by the patient of abdominal musculature of
the patient.
[0069] In a preferred application, the control unit is adapted to
evaluate the imminence of the urge event responsive to an amount of
time elapsed since the patient last voided.
[0070] Preferably, the sensor is adapted to be coupled to the
patient's bladder, and includes a pressure sensor, an acceleration
sensor, and/or an ultrasound transducer.
[0071] There is also provided, in accordance with a preferred
embodiment of the present invention, a device, including:
[0072] a first sensor, which is adapted to be coupled to a bladder
site of a patient and to generate a first signal, responsive to a
pressure in the bladder;
[0073] a second sensor, which is adapted to be coupled to an
abdominal site of the patient and to generate a second signal,
responsive to an overall pressure in the abdomen;
[0074] at least one electrode, which is adapted to be coupled to a
pelvic site of the patient; and
[0075] a control unit, which is adapted to receive the first and
second signals, analyze the signals so as to distinguish between
two conditions of the patient, and apply an electrical waveform to
the at least one electrode, responsive to analyzing the
signals.
[0076] Preferably, the first sensor includes a first pressure
sensor, and wherein the second sensor includes a second pressure
sensor.
[0077] In a preferred embodiment, the control unit is adapted to:
(a) analyze the first and second signals so as to detect a
characteristic in the first signal and a characteristic in the
second signal, (b) identify whether the characteristic in the first
signal is a significant change thereof and whether the
characteristic in the second signal is a significant change thereof
that generally corresponds in time to the change in the first
signal, and (c) configure the waveform responsive to step (b).
[0078] Alternatively or additionally, the control unit is adapted
to: (a) analyze the first and second signals so as to detect a
characteristic in the first signal and a characteristic in the
second signal, (b) identify whether the characteristic in the first
signal is a significant change thereof and whether the
characteristic in the second signal is a significant change thereof
that generally corresponds in time to the change in the first
signal, (c) apply a first waveform to the at least one electrode if
the analysis identifies the change in the first signal as generally
corresponding in time to the change in the second signal, and (d)
apply to the at least one electrode a second waveform, different
from the first waveform, if the analysis identifies the change in
the first signal as not generally corresponding in time to the
change in the second signal. In this case, the control unit is
preferably adapted to configure the first waveform for treatment of
stress incontinence of the patient, and wherein the control unit is
adapted to configure the second waveform for treatment of an urge
disorder of the patient.
[0079] There is further provided, in accordance with a preferred
embodiment of the present invention, a device, including:
[0080] a sensor, which is adapted to generate a signal responsive
to a state of a patient;
[0081] at least one electrode, which is adapted to be coupled to a
pelvic site of the patient; and
[0082] a control unit, which is adapted to receive the signal, to
analyze the signal so as to determine a likelihood of imminent
fecal incontinence, and, responsive to analyzing the signal, to
apply an electrical waveform to the at least one electrode.
[0083] Preferably, the control unit is adapted to configure the
waveform so as to stimulate an anal sphincter muscle to contract.
Alternatively or additionally, the at least one electrode is
adapted to be implanted so as to stimulate a nerve in the pelvic
region of the patient. In a preferred embodiment, the at least one
electrode is adapted to be implanted in contact with a pelvic
muscle of the patient.
[0084] The control unit is preferably adapted to configure the
waveform to have (a) a frequency component between about 40 and 50
Hz, (b) an amplitude between about 3 and 9 V, (c) a series of
pulses having widths between about 0.05 and 1 ms, and/or (d) a
duration between about 1 and 20 seconds.
[0085] Preferably, the at least one electrode includes a single
monopolar electrode and/or at least one electrode includes a pair
of bipolar electrodes. The at least one electrode typically
includes a flexible intramuscular electrode.
[0086] In a preferred embodiment, the at least one electrode and
the control unit are adapted to be implanted in the body of the
patient.
[0087] In a preferred embodiment, the control unit is adapted to
receive an input from the patient and to apply the waveform
responsive to the input.
[0088] For some applications, the control unit is adapted to
analyze the signal so as to distinguish between: (a) a first
signal, indicative of imminent fecal incontinence, and (b) a second
signal, indicative of voluntary voiding by the patient. For
example, the control unit may be adapted to distinguish between the
first and second signals responsive to a rate of change of the
signal generated by the sensor. Alternatively or additionally, the
control unit is adapted to gather information regarding the signal
over an extended period and to analyze the information to find a
pattern characteristic of the patient, for use in determining when
imminent fecal incontinence is likely. In this case, the control
unit is typically adapted to associate with the pattern a
time-varying threshold to which a level of the signal is
compared.
[0089] Typically, the sensor is adapted to be implanted at a pelvic
location of the patient, and includes a pressure sensor, an
acceleration sensor, an ultrasound transducer, and/or a sensing
electrode. In a preferred embodiment, the sensor includes the at
least one electrode.
[0090] For some applications, the sensor is adapted to generate the
signal responsive to a level of filling of the rectum of the
patient, and the control unit is adapted to apply the waveform to
the at least one electrode responsive to the signal. In this case,
the sensor typically includes a pressure sensor. Preferably, the
control unit is adapted to increase a parameter of the waveform
responsive to a level of the signal. Further preferably, the
control unit is adapted to configure the waveform to be such as to
induce afferent signaling in the patient, e.g., to be such as to
induce in the patient afferent signaling of a form which induces a
conscious sensation of rectal filling. In this latter case, the
control unit is typically adapted to configure the waveform to be
such as to induce in the patient afferent signaling of a form which
induces a conscious sensation of rectal filling and an urge to
voluntarily contract an anal sphincter muscle of the patient.
Alternatively or additionally, the control unit is adapted to
configure the waveform to be such as to induce afferent signaling
in the patient of a form that induces contraction of a smooth
muscle in a pelvic region of the patient and inhibits fecal
incontinence.
[0091] There is yet further provided, in accordance with a
preferred embodiment of the present invention, a device,
including:
[0092] at least one electrode, which is adapted to be coupled to a
pelvic muscle of a patient; and
[0093] a control unit, which is adapted to drive the at least one
electrode to apply to the muscle an electrical waveform configured
to reduce patient pain due to interstitial cystitis.
[0094] For some applications, the control unit is adapted to
receive an input from the patient and to apply the waveform
responsive to the input. Alternatively or additionally, the control
unit is adapted to drive the at least one electrode responsive to
an amount of time elapsed since the patient last voided.
[0095] The control unit is typically adapted to configure the
waveform so as to induce relaxation of a bladder muscle of the
patient.
[0096] In a preferred embodiment, the control unit is adapted to
configure the waveform to have (a) a frequency component between
about 5 and 15 Hz, (b) an amplitude between about 1 and 4 V, (c) a
series of pulses having widths between about 0.05 and 0.2 ms,
and/or (d) a duration of about 10-30 minutes. Alternatively or
additionally, the control unit is adapted to configure the waveform
to include a rise time lasting between about 1 second and 3 minutes
prior to attaining a designated waveform application voltage.
Further alternatively or additionally, the control unit is adapted
to configure the waveform to include a decay time lasting between
about 1 second and 3 minutes, prior to returning to a baseline
voltage.
[0097] For some applications, the control unit is adapted to
configure the waveform to have a duty cycle between about 5% and
15%.
[0098] There is still further provided, in accordance with a
preferred embodiment of the present invention, a device,
including:
[0099] a sensor, which is adapted to generate a signal responsive
to a state of a patient;
[0100] at least one electrode, which is adapted to be coupled to an
anatomical site of the patient; and
[0101] a control unit, which is adapted to receive the signal, to
analyze the signal so as to determine a likelihood of imminent
patient pain due to interstitial cystitis, and, responsive to
analyzing the signal, to apply to the at least one electrode an
electrical waveform configured to reduce patient pain due to
interstitial cystitis.
[0102] For some applications, the sensor includes a sensing
electrode adapted to sense electrical activity of a bladder muscle
of the patient.
[0103] Alternatively or additionally, the control unit is adapted
to evaluate the imminence of the interstitial cystitis responsive
to an amount of time elapsed since the patient last voided.
[0104] In a preferred embodiment, the control unit is adapted to
receive an indication of a fill level of the patient's bladder and
to inhibit application of the electrical waveform when the fill
level of the bladder is low.
[0105] Preferably, the control unit is adapted to analyze the
signal so as to distinguish between: (a) a first signal, indicative
of imminent interstitial cystitis, and (b) a second signal,
indicative of voluntary voiding by the patient. For example, the
control unit may be adapted to distinguish between the first and
second signals responsive to a rate of change of the signal
generated by the sensor. Alternatively or additionally, the control
unit is adapted to gather information regarding the signal over an
extended period and to analyze the information to find a pattern
characteristic of the patient, for use in determining when imminent
interstitial cystitis is likely. In this case, the control unit is
preferably adapted to associate with the pattern a time-varying
threshold to which a level of the signal is compared.
[0106] In a preferred embodiment, the sensor includes a pressure
sensor, and the control unit is adapted to analyze a rate of change
of the received signal, and to identify the imminent interstitial
cystitis responsive to a low rate of change of the received
signal.
[0107] In a preferred application, the sensor is adapted to be
implanted at an abdominal site of the patient, and the sensor is
adapted to generate the signal with a low rate of change responsive
to voluntary contraction by the patient of abdominal musculature of
the patient.
[0108] Typically, but not necessarily, the sensor is adapted to be
coupled to the patient's bladder, and comprises a pressure sensor,
an acceleration sensor, and/or an ultrasound transducer.
[0109] Preferably, the at least one electrode and the control unit
are adapted to be implanted in the body of the patient. In this
case, the at least one electrode is adapted to be implanted so as
to stimulate a nerve in the pelvic region of the patient.
Alternatively or additionally, the at least one electrode is
adapted to be implanted in contact with a pelvic muscle of the
patient.
[0110] There is additionally provided, in accordance with a
preferred embodiment of the present invention, a device,
including:
[0111] at least one electrode, which is adapted to be coupled to a
pelvic muscle of a patient; and
[0112] a control unit, which is adapted to drive the at least one
electrode to apply to the muscle an electrical waveform configured
to reduce patient pelvic pain.
[0113] There is still additionally provided, in accordance with a
preferred embodiment of the present invention, a device,
including:
[0114] a sensor, which is adapted to generate a signal responsive
to a state of a patient;
[0115] at least one electrode, which is adapted to be coupled to an
anatomical site of the patient; and
[0116] a control unit, which is adapted to receive the signal, to
analyze the signal so as to determine a likelihood of patient
pelvic pain, and, responsive to analyzing the signal, to apply to
the at least one electrode an electrical waveform configured to
reduce the patient pelvic pain.
[0117] These devices for reducing patient pelvic pain are
preferably configured to be similar to the devices for treating
interstitial cystitis described herein.
[0118] There is yet additionally provided, in accordance with a
preferred embodiment of the present invention, a device,
including:
[0119] a sensor, which is adapted to generate a signal responsive
to a pressure at an abdominal site of a patient;
[0120] at least one electrode, which is adapted to be coupled to an
anatomical site of the patient; and
[0121] a control unit, which is adapted to receive the signal, to
analyze a characteristic of the signal so as to identify a
voluntary contraction of abdominal musculature of the patient that
indicates an onset of a pelvic condition of the patient, and,
responsive to analyzing the signal, to apply to the at least one
electrode an electrical waveform configured to inhibit the
condition.
[0122] Preferably, the sensor includes a pressure sensor, and the
control unit is adapted to analyze a rate of change of the received
signal, and to identify the voluntary contraction responsive to a
low rate of change of the received signal.
[0123] There is also provided, in accordance with a preferred
embodiment of the present invention, a device, including:
[0124] at least one electrode, which is adapted to be implanted at
a pelvic muscle site of a patient; and
[0125] a control unit, which is adapted to drive the at least one
electrode to apply to the muscle an electrical waveform configured
to inhibit urine retention of the patient.
[0126] Typically, but not necessarily, the control unit is adapted
to receive an input from the patient and to apply the waveform
responsive to the input.
[0127] The control unit is preferably adapted to configure the
waveform to have (a) a frequency component between about 1 and 10
Hz, (b) an amplitude between about 3 and 9 V, (c) a series of
pulses having widths between about 0.05 and 0.2 ms, and/or (d) a
duration of about 20-45 seconds.
[0128] For some applications, the control unit is adapted to
configure the waveform to include a rise time lasting between about
1 second and 5 seconds prior to attaining a designated waveform
application voltage. Alternatively or additionally, the control
unit is adapted to configure the waveform to include a decay time
lasting between about 1 second and 5 seconds prior to returning to
a baseline voltage.
[0129] The control unit is preferably adapted to configure the
waveform to have a duty cycle between about 50% and 100%.
[0130] There is further provided, in accordance with a preferred
embodiment of the present invention, a method for implanting a
medical device in a patient, including:
[0131] creating a suprapubic incision in the patient;
[0132] creating a vaginal mucosa incision in the patient;
[0133] passing between the two incisions an electrode lead which is
adapted for coupling to the medical device; and
[0134] implanting the medical device in the patient.
[0135] Preferably, implanting the device includes implanting a
device which is capable of treating a stress incontinence condition
of the patient, an urge incontinence condition of the patient, an
urge frequency condition of the patient, a fecal incontinence
condition of the patient, an interstitial cystitis condition of the
patient, a chronic pelvic pain condition of the patient, and/or a
urine retention condition of the patient.
[0136] In a preferred embodiment, passing the electrode lead
includes subcutaneously passing an inter-incision introducer
between the two incisions, and passing the electrode lead through
the introducer. In this case, the method preferably also
includes:
[0137] removing the inter-incision introducer, so as to leave an
end of the electrode lead accessible;
[0138] inserting a second introducer into the vaginal mucosa
incision, such that a distal end of the second introducer is
proximate a urethral sphincter site of the patient;
[0139] inserting the end of the electrode lead through the second
introducer; and
[0140] securing the lead to the urethral sphincter site.
[0141] The present invention will be more fully understood from the
following detailed description of the preferred embodiments
thereof, taken together with the drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0142] FIG. 1A is a schematic, pictorial view of an implantable
device for prevention of mixed incontinence, in accordance with a
preferred embodiment of the present invention;
[0143] FIG. 1B is a schematic, pictorial view of an implantable
device for prevention of mixed incontinence, in accordance with
another preferred embodiment of the present invention;
[0144] FIGS. 2A, 2B, 2C, 2D, 2E, 2F, and 2G show steps in an
implantation procedure of a stimulation device, in accordance with
a preferred embodiment of the present invention;
[0145] FIG. 2H is a schematic, partly sectional illustration
showing implantation of the device of FIG. 1A in the pelvis of a
patient, in accordance with another preferred embodiment of the
present invention;
[0146] FIG. 2I is a schematic, partly sectional illustration
showing implantation of the device of FIG. 1A in the pelvis of a
patient, in accordance with yet another preferred embodiment of the
present invention;
[0147] FIG. 3 is a schematic block diagram illustrating circuitry
used in an implantable muscle stimulation device, in accordance
with a preferred embodiment of the present invention;
[0148] FIG. 4 is a schematic block diagram illustrating circuitry
used in an implantable muscle stimulation device, in accordance
with another preferred embodiment of the present invention;
[0149] FIG. 5 is a schematic block diagram illustrating signal
processing circuitry for analyzing electromyogram signals, in
accordance with a preferred embodiment of the present
invention;
[0150] FIGS. 6-9 are graphs showing simulated and measured signals,
representative of different aspects of use of an implantable muscle
stimulation device, in accordance with a preferred embodiment of
the present invention;
[0151] FIG. 10A is a schematic diagram of a pressure sensor, in
accordance with a preferred embodiment of the present invention;
and
[0152] FIG. 10B is a schematic, sectional illustration of the
bladder of a patient, showing implantation therein of the pressure
sensor of FIG. 10A, in accordance with a preferred embodiment of
the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0153] I. Overview of Preferred Embodiments
[0154] A. General description of stimulator device
[0155] B. Sensing and control functions of the device
[0156] C. Signal processing
[0157] D. Power consumption control
[0158] II. Detailed Description of Figures
[0159] A. External elements of a stimulator device
[0160] B. Anatomical and surgical considerations
[0161] C. Signal processing
[0162] (i) hardware and algorithms
[0163] (ii) simulation of a typical EMG
[0164] (iii) experimentally measured EMG signals: distinguishing
incontinence from voluntary voiding
[0165] D. Muscle stimulation
[0166] E. Provision of power to the control unit
[0167] F. External communication with the control unit
[0168] G. Utilization of other sensors
[0169] H. Reduction of power consumption
[0170] I. Overview of Preferred Embodiments
[0171] A. General Description of Stimulator Device
[0172] Various aspects of the present invention are described in
this section (I) and in greater detail in the following section
(II). As described with reference to the preferred embodiments
shown in FIGS. 1A and 1B, an electronic stimulator device is
preferably implanted in the genital region of a patient who has at
least two types of incontinence. The device stimulates one or more
of the muscles or nerves in the region, so as to control and treat
the patient's incontinence. A preferred method for implanting the
device is shown in FIGS. 2A, 2B, 2C, 2D, 2E, 2F, and 2G.
[0173] Preferably, imminent urge or stress incontinence generates
an electromyographic (EMG) signal in the muscles, which is sensed
by one or more electrodes and is analyzed by a control unit of the
device. Alternatively or additionally, non-electromyographic
signals (e.g., pressure signals) are received and analyzed by the
control unit. When the control unit determines that the signals are
indicative of a condition that is likely to cause involuntary urine
flow from the bladder, it applies an electrical waveform to the one
or more electrodes, which is configured to treat the particular
type of incontinence detected (e.g., stress or urge), in order to
stimulate a pelvic muscle to contract and inhibit the urine flow.
It is to be understood that although some preferred embodiments of
the present invention are described herein with respect to
interpreting EMG signals so as to identify the onset of a
particular condition, in many of these embodiments, analysis of
pressure signals or other non-EMG signals may be performed instead
of or in addition to the analysis of the EMG signals.
[0174] B. Sensing and Control Functions of the Device
[0175] In addition to EMG sensing electrodes, the device preferably
also comprises one or more other physiological sensors, described
hereinbelow with reference to FIGS. 2H, 2I, 3, 4, 10A, and 10B,
which generate signals responsive to, for example, motion,
intravesical or abdominal pressure, or urine volume in the bladder.
These signals are indicative of some forms of incontinence.
[0176] Typically, when the urine volume in the bladder is low,
there will be no urine flow even when the abdominal pressure does
increase. As described with reference to a plurality of the
figures, the control unit preferably processes the signals from the
various sensors and uses them to determine when the electrical
stimulation should be applied to the muscles.
[0177] C. Signal Processing
[0178] Preferably, the control unit comprises a processor, e.g., as
described with reference to FIGS. 3 and 4, which is additionally
programmed to distinguish between signals indicative of possible
incontinence and other signals that do not warrant stimulation of a
nerve or muscle. In particular, the processor is preferably
programmed to recognize signal patterns indicative of normal
voiding, and does not stimulate the muscles when such patterns
occur, so that the patient can pass urine normally. Detection of
normal voiding is described in more detail with reference to FIGS.
7 and 8.
[0179] Preferably, the processor analyzes both long-term and
short-term variations in the signals, as well as rates, spectral
patterns, and patterns of change in the signals. For example, to
inhibit stress incontinence, the processor may set a threshold of
an aspect of the EMG signal that varies over time responsive to an
assessment of the patient's physiological condition. Subsequently,
the processor applies the stimulation only when a transient
variation in the aspect of the EMG signal exceeds the threshold.
Methods for modifying the threshold in real time are described with
reference to FIG. 6.
[0180] In the context of the present patent application and in the
claims, a "time-varying threshold" is to be understood as
comprising substantially any appropriate time-varying detection
parameters that a person skilled in the art, having read the
disclosure of the present patent application, would consider useful
in applying the principles of the present invention. By way of
illustration and not limitation, these time-varying detection
parameters may include magnitude, rate, or other aspects of the EMG
signal, or of quantitative ultrasound, pressure, or acceleration
measurements, as described herein.
[0181] D. Power Consumption Control
[0182] As described with reference to FIG. 5, the control unit
preferably comprises a low-power, low-speed processor, which
monitors the EMG and/or sensor signals continuously, and a
high-speed processor, which turns on only when the low-speed
processor detects an increase in EMG or other activity. Use of the
two processors has been shown to significantly reduce consumption
of electrical power. The high-speed processor performs an accurate
analysis of the signals to determine whether stimulation is
actually warranted.
[0183] Alternatively or additionally, the concepts described herein
with respect to two independent processors may be applied using a
single processor having two modes of operation--a low power, low
capacity mode, and a high power, high capacity mode.
[0184] II. Detailed Description of Figures
[0185] A. External Elements of a Stimulator Device
[0186] Reference is now made to FIG. 1A, which is a schematic,
pictorial illustration of an implantable electronic stimulator
device 20, in accordance with a preferred embodiment of the present
invention. Device 20 is preferably implanted in the pelvic region
of a patient, as described further hereinbelow, for use in
providing muscle and/or nerve stimulation so as to control and
treat urinary urge and stress incontinence.
[0187] Device 20 comprises a control unit 22 and electrodes 27 and
29, coupled thereto by electrical leads 24. Additionally, device 20
preferably comprises at least one additional physiological sensor
44, such as a miniature ultrasound transducer, one or more
accelerometers, a pressure transducer or other sensors known in the
art.
[0188] The control unit preferably comprises circuitry for sensing
electrical signals received by electrodes 27 and 29, such as
electromyogram (EMG) signals, along with circuitry for processing
the signals from sensor 44. Control unit 22 additionally comprises
circuitry for applying electrical stimulation waveforms to one or
both of the electrodes responsive to the signals. Details of
control unit 22 and electrodes 27 and 29 are preferably as
described in the above-cited PCT Patent Publications WO 00/19940,
entitled "Incontinence Treatment Device," and WO 00/19939,
entitled, "Control of urge incontinence," with appropriate changes
as described herein or as are otherwise indicated by clinical and
engineering considerations that will be clear to those skilled in
the art.
[0189] The electrodes are preferably flexible intramuscular-type
wire electrodes, about 1-5 mm long and 50-100 microns in diameter,
thus designed to minimize patient discomfort. They are typically
formed in the shape of a spiral or hook, as is known in the art, so
that they can be easily and permanently anchored in the muscle. The
wire from which the electrodes are made comprises a suitable
conductive material, preferably a biocompatible metal such as
silver, a platinum/iridium alloy (90/10) or a nickel/chromium
alloy. Leads 24 are preferably 5-10 cm long and surrounded by an
insulating jacket typically comprising nylon, polyurethane, Teflon
or another flexible, biocompatible insulating material. An optional
additional wire (not shown) inside the jacket serves as an antenna
for the purpose of wireless communications with device 20, as
described further hereinbelow.
[0190] Control unit 22 preferably comprises circuitry for
processing electrical signals received from electrodes 27 and 29
and for applying a waveform to the electrodes. The circuitry is
preferably contained in a case made of titanium or other suitable
biocompatible metal. Typically, the case is about 20 mm in diameter
and 4 mm thick. For some applications, the case serves as a ground
electrode for electrodes 27 and 29 when they are sensing or
stimulating in a monopolar mode. Alternatively, the case may
comprise metal coated with a layer of biocompatible plastic, such
as polymethyl methacrylate (PMMA) or silicone. Although two
electrodes and one sensor are shown attached to the control unit in
FIG. 1A, it is possible to use only a single electrode or,
alternatively, additional electrodes and/or other sensors, as
described further hereinbelow.
[0191] FIG. 1B is a schematic, pictorial illustration of electronic
stimulator device 20, in accordance with another preferred
embodiment of the present invention. Except with respect to the
differences described hereinbelow, the embodiment shown in FIG. 1B
is generally similar to the embodiment shown in FIG. 1A, and
techniques described herein with respect to one of the
configurations can generally be applied to the other configuration,
mutatis mutandis.
[0192] A lead 21 is preferably provided to couple control unit 22
to a pelvic muscle of the patient. Lead 21 is secured to the muscle
by means of a fixation helix 23 or other techniques known in the
art, so as to provide electrical contact between the muscle and two
stimulation electrodes 26 and 30 disposed on a silicon casing 19 of
the lead. Each electrode is typically less than about 80 mm in
length, and is most preferably approximately 3 mm in length. The
electrodes are typically separated by approximately 3 mm along the
length of lead 21. In this space between electrodes 26 and 30, a
tip 15 of an EMG wire 17 may protrude approximately 100 microns
through casing 19, for those applications in which EMG sensing is
desirable. Typically, the diameter of wire 17 is approximately 50
microns, and the diameter of casing 19 is approximately 1.5 mm.
[0193] B. Anatomical and Surgical Considerations
[0194] FIGS. 2A, 2B, 2C, 2D, 2E, 2F and 2G show a method for
implantation of a pelvic stimulation device, in accordance with a
preferred embodiment of the present invention. It is emphasized
that although this implantation method represents a preferred
method, other procedures, including those known in the art, may
also be adapted for use with other embodiments of the present
invention. For illustrative purposes, the procedure is shown when
performed upon a female patient. Unlike many implantation
procedures known in the art, the implantation procedure provided by
this embodiment is typically performed under local anesthesia, with
the patient placed in the lithotomy position. It will be
appreciated that the surgical procedure shown in these figures has
further benefits over many similar prior art implantation
procedures, in that the complication rate resulting therefrom is
significantly reduced by virtue of its being carried out in a
region substantially devoid of major blood vessels, and in a manner
that avoids risk to delicate structures.
[0195] FIG. 2A shows a 4 cm long "pocket" incision 170, made
approximately 1 cm cephalad to the pubic bone in order to create a
pocket in the subcutaneous tissue adjacent to the fascia. A control
unit will later be introduced into this pocket.
[0196] FIG. 2B shows a vaginal mucosa incision 172. This second
incision, approximately 0.5-1 cm long, is preferably made through
the vaginal mucosa until the subcutaneous tissue, at a site
approximately 0.5-1 cm anterior and lateral to the urethral
meatus.
[0197] FIG. 2C shows the creation of a subcutaneous tunnel 174
using a 12 Fr introducer 176, placed in incision 172, and conveyed
subcutaneously until it reaches and exits through incision 170.
[0198] FIG. 2D shows the insertion of a stimulation lead 178
through introducer 176 until its exit at the lower end of the
introducer.
[0199] FIG. 2E shows a stimulation lead tip 182 remaining outside
incision 172 after the removal of introducer 176.
[0200] FIG. 2F shows the reinsertion of stimulation lead 178 into
incision 172. A 5 Fr splittable short introducer 180 is inserted
into incision 172, adjacent to lead 178. The introducer is aimed
slightly medially, i.e., towards the urethra, care being taken not
to injure the urethra. Introducer 180 is pushed for a distance of
approximately 2.5 cm, to a site 0.5-1 cm lateral to the urethral
wall. The free end of stimulation lead 178 is reinserted and
advanced through short introducer 180 into the urethral sphincter.
Once the stimulation lead is properly secured, introducer 180 is
withdrawn by being split into two parts. A 3/0 nylon suture is made
in the subcutaneous tissue around the stimulation lead.
Subsequently, the free electrode lead is buried subcutaneously, and
incision 172 is closed by a 3/0 plain catgut or Dexon suture.
[0201] An 8 Fr introducer (not shown) is inserted through incision
170, between the fascia and muscle tissue, so as to reach the
retropubic space. A sensor lead (not shown) for a pressure or
electrical sensor is advanced through the introducer to a desired
position, e.g., in the retropubic space or between fascia and
muscle. Following placement of the lead, it is secured to the
fascia by a 3/0 nylon suture. Once the sensor has been properly
secured, the lead stylet is withdrawn from the introducer, and the
introducer is then removed. Connectors for the sensor lead are
connected to appropriate sites on the control unit.
[0202] FIG. 2G shows the insertion of a control unit 184 through
incision 170. After initial verification of the performance of the
implanted system, incision 170 is closed with two layers.
[0203] FIG. 2H is a schematic, partly sectional illustration
showing the genitourinary anatomy of a female patient 31 in whom
device 20 is implanted, in accordance with another preferred
embodiment of the present invention. It will be understood that,
with appropriate changes, device 20 may be implanted in or coupled
to a male patient. In this embodiment, electrode 27 is inserted
into a muscle 32, such as the levator ani muscle, in a vicinity of
urethra 34 and bladder 36. Electrode 29 is inserted into the
patient's detrusor muscle 37, which surrounds bladder 36.
Alternatively or additionally, electrodes 27 and 29, or additional
electrodes not shown in the figure, may be placed in or adjacent to
other muscles of the pelvic floor.
[0204] The precise placement of the electrodes is typically not
essential, particularly since electrical signals tend to pass among
the different muscles in the region. Thus, any placement of the
electrode in or on one or more of the pelvic muscles suitable for
exercising urine control is considered to be within the scope of
this embodiment of the present invention. The electrodes are
preferably inserted through an incision made in the wall of vagina
42. Alternatively, another suitable approach may be chosen for ease
of access and minimization of tissue trauma.
[0205] Control unit 22 is preferably implanted under the skin in
the genitopelvic region of patient 31. Most preferably, the control
unit is implanted inside the patient's labia minora 38 or in the
labia majora 40. Alternatively, the control unit is not implanted
in the patient's body, but is instead maintained outside the body,
connected by leads 24 to the electrodes. This configuration is
convenient particularly for an initial test period, during which
the effectiveness of device 20 in treating a given patient is
evaluated before permanent implantation.
[0206] FIG. 2I is a schematic, partly sectional illustration
showing the genitourinary anatomy of patient 31 in whom device 20
is implanted, in accordance with yet another preferred embodiment
of the present invention. Preferably, control unit 22 is implanted
in a vicinity of the sacral spine, as shown, but may alternatively
be implanted in the abdomen or in the pelvis. According to this
embodiment, the control unit drives electrode 27 to stimulate a
nerve that innervates one or more muscles which are responsible for
urine control. Typically, a sacral nerve is stimulated, so as to
control the flow of urine from the bladder.
[0207] Generally, the choice of implantation location for the
control unit, as well as which particular nerve is to be
stimulated, is made by the patient's physician, responsive to the
patient's condition and other surgical considerations. Preferably,
electrode 29 (FIG. 2H), is implanted in the detrusor muscle or in
another pelvic muscle, and detects EMG signals, which are conveyed
for analysis by the control unit. Alternatively or additionally,
bladder pressure and volume sensors (not shown) and electrode 29
convey signals to the control unit responsive to bladder
contractions associated with imminent incontinence, whereupon the
control unit: (a) analyzes the signals to distinguish between
aspects thereof indicative of stress incontinence and aspects
thereof indicative of urge incontinence, and (b) drives electrode
27 to stimulate the sacral nerve and/or drives electrode 29 to
stimulate the pelvic muscle, using stimulation parameters
appropriate for treating the identified form of urinary
incontinence.
[0208] C. Signal Processing
[0209] (i) Hardware and Algorithms
[0210] FIG. 3 is a schematic block diagram showing circuitry used
in control unit 22 to receive signals from and apply electrical
waveforms to electrode 27, in accordance with a preferred
embodiment of the present invention. Although in this embodiment
device 20 is described as operating in a monopolar mode, the
principles described hereinbelow are applicable to bipolar
operation as well, in which both electrodes 27 and 29 are
active.
[0211] Electrode 27 receives EMG signals from muscle 32, which are
conveyed via a normally-closed switch 46 to the input of an
amplifier 48, preferably a low-noise operational amplifier.
Amplified signals output from amplifier 48 are digitized by an
analog/digital (A/D) converter 50 and conveyed to a central
processing unit (CPU) 52, preferably a microprocessor. Preferably,
although not necessarily, the amplified signals are not rectified
prior to being digitized, to allow various forms of analysis, for
example, spectral analysis, to be performed on the raw data,
without the distortion imparted by rectification. CPU 52 preferably
analyzes these signals and/or signals from other physiological
sensors, such as ultrasound, pressure, strain, and acceleration
sensors described hereinbelow, to determine whether they fit a
pattern indicating that incontinence is likely to result, and, if
so, to determine the type of incontinence. The analysis preferably
comprises a spectral analysis and an analysis of EMG signal
magnitude and rate. Responsive to a determination that a particular
form of incontinence is likely, a pulse generator 54 conveys
electrical pulses to electrode 27, as described hereinbelow.
[0212] Optionally, sensor 44 (FIGS. 1A and 1B) comprises a
miniaturized ultrasound transducer, which is implanted in proximity
to bladder 36. Additionally or alternatively, sensor 44 comprises a
pressure sensor filled with silicon oil, as shown schematically in
FIG. 10A. Further alternatively or additionally, sensor 44
comprises a pressure sensor in the bladder, bladder wall, or
elsewhere in the abdominal cavity; a strain sensor sutured to the
bladder wall; or a sensor which detects action potentials in the
bladder muscle. Most preferably, sensor 44 comprises each of these.
Signals from the transducer or sensor are conveyed to control unit
22 for analysis, particularly so as to enable the control unit to
estimate the urine volume within the bladder. When the bladder is
relatively empty, there is no need to actuate electrodes 27 and 29,
even when a transient increase in the electromyogram (EMG) signal
or another signal would otherwise indicate an increased probability
of imminent incontinence. Alternatively or additionally, the EMG
signal itself may be analyzed to gain an indication of the urine
volume in the bladder, since when the bladder is full, the average
EMG activity typically increases. Further alternatively or
additionally, analysis such as that described hereinbelow with
reference to FIG. 9 may be carried out, typically so as to
determine the likelihood of imminent urge incontinence.
[0213] The CPU is preferably programmed to distinguish between
incontinence-related patterns and other signal patterns not
associated with incontinence, such as signals generated when
patient 31 wishes to pass urine voluntarily. Preferably, the CPU
gathers long-term statistical information regarding the EMG and the
signals from the other sensors, and analyzes the information to
"learn" common signal patterns that are characteristic of patient
31. The learned patterns are used in refining decision criteria
used by the CPU in determining whether or not to apply waveforms to
the electrodes. For some applications, a handheld controller (not
shown) receives an input from the patient whenever urine is
unintentionally passed, and control unit 22 modifies signal
analysis parameters and/or stimulation parameters responsive
thereto, so as to reduce the likelihood of future incontinence.
[0214] (ii) Simulation of a Typical EMG
[0215] FIG. 6 is a graph that schematically illustrates results of
a simulation experiment, in accordance with a preferred embodiment
of the present invention, including a simulated EMG signal 100 of a
woman suffering from stress incontinence. A variable, adaptive
threshold level 102 is marked on the graph. Over the course of
several hours, as the woman's bladder fill level increases, the
average level of EMG signal 100 increases accordingly. In this
example, threshold level 102 is computed so as to increase as a
function of the average EMG. Alternatively or additionally,
threshold level 102 and a plurality of other time-varying detection
parameters are calculated as functions of other features of the EMG
signal or of other aspects of the woman's condition (particularly
as measured by sensors 44, 76 and 78 (FIG. 4)), and are used
separately or in combination in determining whether to apply
stimulation to inhibit involuntary urine flow. As shown, adaptive
threshold level 102 enables five possible incidents of
incontinence, marked by excursions 104 of signal 100 over level
102, to be detected reliably, with a low false alarm rate. On the
other hand, if a fixed threshold level 106 is used, as is known in
the art, some EMG excursions 104 are missed (at t=60 and 110
minutes), and, moreover, the false alarm rate is high (at t>220
minutes).
[0216] (iii) Experimentally Measured EMG Signals: Distinguishing
Incontinence From Voluntary Voiding
[0217] FIG. 7 includes graphs 110 and 112 that schematically
illustrate experimental measurements made before, during and after
voluntary voiding of urine, in accordance with a preferred
embodiment of the present invention. Graph 112 is a continuation in
time of graph 110. The upper trace in both graphs illustrates urine
flow, wherein the beginning and end of voluntary flow are marked by
arrows. The lower trace illustrates measured EMG signals.
[0218] In a period preceding voiding, an EMG signal 114 shows
substantial high-frequency activity, which is generally indicative
of a full bladder. High-frequency spikes in signal 114 (of which
none appear in FIG. 7) would be interpreted by CPU 52 as signs of
imminent incontinence, leading to actuation of pulse generator 54.
On the other hand, voluntary voiding is preceded by a portion 116
of the EMG signal, in which there is a large but gradual increase
in the signal level. EMG signal portion 116 is associated with
voluntary activation of the pelvic floor muscles for the purpose of
passing urine from the bladder, as is a later signal portion 118
during the same act of voiding. Therefore, CPU 52 preferably
analyzes not only the level of the EMG signals, but also a rate of
change of the signals, in order to distinguish between voluntary
and involuntary contractions of the pelvic muscles. When the rate
of change is characteristic of voluntary voiding, no stimulation is
applied by pulse generator 54.
[0219] FIG. 8 (not to scale) includes two graphs, showing: (a) data
recorded during a series of periods A, B, C and D, representing
stages before, during, and after urination, and (b) preferred times
with respect to these periods for activation of pulse generator 54
in order to inhibit urge incontinence, in accordance with a
preferred embodiment of the present invention. Bladder pressure
data 140 and EMG data 150 shown in FIG. 8 are based on text and a
figure in the above-referenced book, Urinary Incontinence (p. 35),
which describes the voluntary voiding of a healthy adult human
female subject. Preferably, inputs to control unit 22 include the
EMG data and bladder pressure data, to enable the control unit to
determine an appropriate time to activate the pulse generator.
[0220] During period A, the bladder fills, which filling is
preferably detected and identified as such by the control unit.
Notably, in period A there is a slow, steady increase in bladder
pressure, as well as a slow, steady increase in peak-to-peak
amplitude of the EMG signal. Bladder pressure is seen to increase
sharply during voiding period B, in comparison to the slow increase
of period A. During period C, voiding was terminated. During period
D, the bladder fills again, in substantially the same manner as in
period A. Examination of periods B and C shows that the EMG signal
has essentially zero magnitude during voiding and during its
termination, and generally increases with increasing bladder
pressure during the bladder-filling periods A and D.
[0221] Preferably, control unit 22 identifies an initiation time of
normal voiding by analysis of the EMG and/or bladder pressure data.
In a preferred embodiment, the control unit actuates pulse
generator 54 to apply pulses to electrodes 27 and/or 29 at a
predetermined time after voiding. For example, in an interview
conducted during the calibration period, it may be determined that
a particular patient generally only experiences urge incontinence
greater than 1.5 hours following voluntary voiding. The control
unit may then be programmed to detect voiding and initiate pulse
application one hour thereafter, and to continue the pulse
application until a subsequent onset of voluntary voiding is
detected.
[0222] Alternatively or additionally, the pulse generator may be
actuated by the control unit when the average magnitude of the EMG
exceeds a specified threshold, because the likelihood of urge
incontinence reflects the increased bladder pressure indicated by
the EMG signal exceeding the threshold. Further alternatively or
additionally, the calibration period may include a training period,
in which the control unit continually samples the EMG signal, and
in which the patient indicates to the control unit whenever urge
incontinence occurs. During or subsequent to the training period,
the control unit or an external processor (not shown) analyzes each
instance of urge incontinence to determine aspects of the EMG
and/or other sensor signals preceding the incontinence which can be
used during regular operation of the unit to predict incontinence.
For many applications of the present invention, the control unit is
operative to execute some or all of the above methods, so as to
minimize or eliminate occurrences of urge incontinence. It will be
appreciated that these strategies may be applied to other types of
incontinence as well, mutatis mutandis.
[0223] FIG. 9 is a graph showing simulated data, for use in
detecting the imminent onset of urge incontinence, in accordance
with a preferred embodiment of the present invention. Preferably,
control unit 22 analyzes a measured pressure-volume (or
pressure-time) relationship of the patient's bladder, so as to
determine whether the pressure is increasing in a healthy manner,
as represented by dashed line 130, or whether it is characterized
by one or more relatively sharp features 132, which may indicate
detrusor instability and imminent urge incontinence. Preferably, if
urge incontinence is deemed likely, then control unit 22 initiates
the stimulation of a pelvic muscle using protocols appropriate for
treating the urge incontinence (described hereinbelow), which are
typically different from those suitable for the treatment of stress
incontinence. Measurement of bladder volume may be performed using
ultrasound techniques or by means of a strain gauge fixed to the
patient's bladder. It is to be understood that whereas a
pressure-volume curve is shown in FIG. 9, a pressure-time curve may
similarly be generated and subsequently interpreted to identify
analogous sharp features indicative of imminent urge
incontinence.
[0224] Alternatively or additionally, the patient is enabled to
instruct control unit 22 to initiate electrical stimulation of the
muscles in order to inhibit urge incontinence which the patient
senses may be imminent. For example, the patient may input the
instruction to the control unit by voluntarily tightening her
abdominal muscles, which in turn causes measurable increases in
abdominal pressure. Advantageously, the rate of increase of
abdominal pressure generated by voluntary contraction of the
abdominal musculature is significantly smaller than that increase
generated involuntarily, for example, during laughter. Typically,
the patient can be taught in a single training session to generate
a detectable and distinguishable muscle contraction, appropriate
for controlling device 20. For some applications, control unit 22
comprises an external input unit, such as a keypad with buttons
designated for certain functions, e.g., "Inhibit urge incontinence
now," or "Inhibit stress incontinence now."
[0225] In a preferred embodiment, stress incontinence and urge
incontinence are distinguished solely (or at least in part)
responsive to differences in d(Pressure)/dt characteristic of the
respective conditions. For example, values of dP/dt greater than a
threshold value are interpreted as being indicative of stress
incontinence, while values of dP/dt less than the threshold are
interpreted as being indicative of urge incontinence.
[0226] D. Muscle Stimulation
[0227] With reference to FIG. 3, when possible stress incontinence
is detected, CPU 52 opens switch 46 and drives pulse generator 54
to apply a suitable electrical waveform to electrode 27 so as to
stimulate muscle 32 to contract and thereby inhibit the
incontinence which was detected. Switch 46 is opened in order to
avoid feedback of the stimulation waveform to amplifier 48, and is
closed again after the waveform is terminated. In the embodiment
shown in FIG. 3, the waveform is applied to the electrode in a
monopolar mode, whereby a case 25 of control unit 22 serves as the
return (ground) electrode. (This mode can be used only when case 25
comprises a conductive material. When control unit 22 has a plastic
case, at least two electrodes on one or more leads are generally
needed, in order to administer bipolar stimulation.)
[0228] For some applications, as muscle 32 contracts, it closes off
urethra 34, thus inhibiting the undesired urine flow. Preferably,
the waveform is terminated and switch 46 is closed after a
predetermined period of time has passed, e.g., 0.5-1 second to
treat stress incontinence and 10 minutes to treat urge
incontinence. Alternatively or additionally, the waveform is
terminated and switch 46 is closed if the patient voids voluntarily
or other new data indicate that the expected incontinence is no
longer likely. If possible incontinence is again detected at this
point, the waveform is re-applied.
[0229] It will be appreciated that, depending on the particular
application, one or more waveforms may be employed in the practice
of various embodiments of the present invention. For example, the
waveform may be monophasic or biphasic and may have a range of
amplitudes, duty cycles and/or frequencies. It has been found
generally that pulse frequencies in the range between 2 and 50 Hz
are effective in engendering contraction of the levator ani and
other pelvic muscles, but for some applications it may be
appropriate to use frequencies outside of this range. Certain
preferred stimulation parameters are described hereinbelow.
[0230] Preferably, but not necessarily, the same electrode or
electrodes are used to treat both stress incontinence and urge
incontinence; however, different stimulation parameters are
utilized depending on the particular form of incontinence which is
immediately to be treated. Alternatively, at least one electrode is
dedicated to treating a particular form of incontinence, e.g., an
electrode implanted so as to stimulate the sacral nerve may be
driven by control unit 22 to apply current most suitable for
treating urge incontinence.
[0231] As described hereinabove, the processor preferably
identifies the form of incontinence based on particular
physiological characteristics detected by the sensors, and control
unit 22 applies an appropriate stimulation signal responsive
thereto. For example, stress incontinence may be detected using
techniques described hereinabove with reference to FIGS. 6 and 7,
and urge incontinence may be detected using techniques described
with reference to FIGS. 8 and 9. In patients with mixed
incontinence, these techniques are typically sufficient to reveal
the significant differences between the two types of incontinence,
e.g., the impulsive pressure and/or EMG spikes in instances of
stress incontinence are generally not present in urge incontinence,
while the pressure-volume and pressure-time features characteristic
of detrusor instability and urge incontinence are correspondingly
not characteristic of stress incontinence.
[0232] For some applications, two sensors are implanted at
different sites within the patient. These generate signals which,
in combination, are analyzed by control unit 22 so as to determine
whether a stress incontinence event or an urge incontinence event
is imminent. In a preferred configuration, one pressure sensor is
coupled to measure intravesical pressure, while another pressure
sensor is coupled to measure intra-abdominal pressure. Sharp
increases in bladder pressure that occur generally simultaneously
with sharp increases in overall abdominal pressure are typically
interpreted to be indicative of possible imminent stress
incontinence, e.g., due to laughter. By contrast, increases in
bladder pressure that are not accompanied by increases in overall
abdominal pressure are interpreted as being indicative of imminent
urge incontinence.
[0233] Responsive to a determination of imminent incontinence, and
the identification of the particular type of incontinence, the
stimulation waveform is preferably applied, typically comprising a
bipolar square wave having characteristics summarized in Table I.
This table also indicates appropriate stimulation parameters for
the treatment of other disorders, such as fecal incontinence,
interstitial cystitis (IC), chronic pelvic pain, and urine
retention, described hereinbelow. For some applications and some
patients, other parameters may also be used.
1 TABLE I Stress and Chronic fecal pelvic pain Urine incon. Urge
event and IC retention Amp. 3-9 0.5-5 1-4 3-9 V V V V Freq. 40-50
5-15 5-15 1-10 Hz Hz Hz Hz Pulse 0.05-1 0.05-1 0.05-0.2 0.05-0.2
width ms ms ms ms Duration 0.2-1 s 5-10 min 10-30 min 20-45 s of
signal (stress); 1-20 s (fecal incon.) Rise time .about.0 0-1 min
0-3 min 0-5 s to peak amp. Decay time .about.0 0-1 min 0-3 min 0-5
s Optional Bursts not 1-5 s on, 2 s on, 20 s 5-10 s on, bursts
used. 20-60 s off. off. 5-10 s off. (Duty Typical duty Typical duty
Typical duty cycle) cycle: cycle: cycle: 5-15% 5-15% 50-100%
[0234] Thus, it is seen that in response to a determination of
imminent stress incontinence, e.g., due to the patient sneezing, a
high-power waveform is applied, typically having both a high
amplitude and a high frequency. This form of stimulation is
generally preferred in inhibiting the rapid onset of stress
incontinence, as the stimulation develops significant muscular
contraction over a very short time period, so as to prevent the
involuntary passing of urine. Shortly after the triggering event
(e.g., the sneeze) has finished, the stimulation is preferably
removed, because the likelihood of imminent incontinence is
diminished.
[0235] By contrast, imminent urge incontinence is typically more
suitably treated over a longer time period. For example, a signal
may be applied from the time that control unit 22 determines that
urge incontinence is imminent until the control unit determines
that the patient has voluntarily voided. Because of the nature of
urge incontinence, i.e., it is characterized by the involuntary and
undesired contraction of bladder muscles, a lower energy waveform
is applied to a spinal site and/or to a pelvic floor muscle. This
lower energy waveform is preferably configured to induce a
relaxation response of the muscle tissue of the bladder, and to
thereby inhibit involuntary urination. Advantageously, since the
treatment of urge incontinence typically does not consume
electrical power at the same rate as the treatment of stress
incontinence, the drain on implanted batteries resulting from the
treatment of urge incontinence is typically low, allowing the
appropriate waveforms to be applied for significantly longer time
periods than those useful for treating stress incontinence.
[0236] For some applications, the waveform for treating urge
incontinence is applied in bursts, e.g., the waveform is applied
for about 1-5 seconds, and then removed for about 20-60 seconds.
Typically, the relatively short bursts are sufficient to provide
the patient with protection against incontinence during the
inter-burst periods. Advantageously, such a protocol of waveforms
in bursts further reduces the consumption of electricity.
[0237] In a preferred embodiment, for example, when treating
patients with severe urge incontinence, it is beneficial to treat
the urge incontinence prophylactically, i.e., more frequently than
when a particular event of urge incontinence is imminent. In this
embodiment, waveforms are typically applied automatically, at a
fixed time after voluntary voiding and/or whenever bladder volume
or pressure exceeds a threshold. Alternatively or additionally, for
some patients, the treatment for urge incontinence is applied
substantially continuously. Preferably, but not necessarily, these
continuous or very-frequent modes of treatment are applied in
bursts, as described hereinabove.
[0238] For some urge incontinence treatment applications, it is
beneficial to extend the initiation of the application of the
waveform over a period ranging from several seconds to about one
minute. Thus, for example, a 10 Hz square wave may be increased to
a designated waveform application voltage of 2 V over a period of 2
seconds, which is generally fast enough to inhibit urge
incontinence, without inadvertently providing a sharp stimulus that
might elicit unintentional voiding. When it is desired to apply the
waveform in intermittent bursts, the amplitude is typically held at
the peak value for approximately 1-5 seconds, and subsequently
caused to decay over a period of several seconds. An extended decay
time is also believed by the inventors to inhibit inadvertently
eliciting the sharp bladder contractions which in some instances
may bring about incontinence.
[0239] Although preferred embodiments of the present invention are
generally described herein with respect to control unit 22
distinguishing between stress incontinence and urge incontinence,
and applying an appropriate treatment responsive thereto, it is to
be understood that other disorders may also be treated some of the
techniques described herein, mutatis mutandis. Thus, for example,
chronic pelvic pain and interstitial cystitis are preferably
treated using stimulation parameters shown in Table I. As in the
treatment of stress or urge incontinence, the patient herself is
typically enabled to activate control unit 22 to treat the
condition. Alternatively or additionally, the control unit is
programmed to apply an appropriate waveform responsive to a
determination of bladder volume (e.g., via an ultrasound
measurement), bladder pressure, and/or based on the time from last
voiding. Voiding is preferably determined using techniques
described herein, such as measuring changes in abdominal pressure,
or analyzing pelvic floor EMG data. Typically, interstitial
cystitis and chronic pelvic pain are treated, like urge
incontinence, using electric signal application parameters
configured to induce relaxation of the bladder.
[0240] As shown in Table I, pathological retention of urine (a
condition common in patients with paraplegia) is preferably treated
by the application to a pelvic floor muscle of a waveform
configured to facilitate voiding. Preferably, the patient is
enabled to enter a command into an external controller whenever
voiding is desired.
[0241] In a preferred embodiment of the present invention, fecal
incontinence is treated by the application of a waveform to a
pelvic floor site or to a site in or adjacent to the anal sphincter
of the patient. Typically, waveform parameters are generally
similar to those for treating stress incontinence. Additionally,
because fecal incontinence often accompanies urinary incontinence,
particularly stress incontinence, the same techniques described
herein for detecting the onset of stress incontinence (e.g., EMG or
pressure measurements) are preferably adapted for use in detecting
the onset of fecal incontinence.
[0242] In normal physiological functioning, an accumulation of
feces in the rectum causes afferent signaling that leads to
involuntary smooth muscle contraction in the pelvic region and to
voluntary contraction of the striated muscle of the anal sphincter.
These contractions of smooth and striated muscle provide the
control required to defer defecation until a desired time. For some
patients, fecal incontinence is caused at least in part by an
impairment of the afferent signaling which should occur responsive
to an accumulation of feces.
[0243] Therefore, in a preferred embodiment of the present
invention, control unit 22 is adapted to enhance the functioning of
this afferent pathway, in order to restore normal levels of smooth
and/or striated muscle contractions, and, consequently, to restore
fecal continence. Preferably, control unit 22 senses the pressure
in the patient's rectum, or senses another parameter indicative of
rectal filling, and drives electrodes implanted in or near the
patient's anal sphincter to apply a signal which generates (or
amplifies) afferent signaling. Typically, this induced afferent
signaling is sufficient to alert the patient to the gradually
increasing level of rectal filling, such that the patient will
naturally respond by tightening the striated muscle of the anal
sphincter. Often, the induced sensation is indistinguishable from
analogous natural sensations experienced by healthy
individuals.
[0244] Advantageously, smooth muscle contractions are also believed
to occur responsive to the induced afferent signaling, such that
after a period of weeks to several months, smooth muscle
contractions are expected to supplement the striated muscle
contractions, and provide enhanced protection against fecal
incontinence.
[0245] For some applications, the magnitude, frequency, and/or duty
cycle of the applied signal is configured to simulate the body's
natural afferent signaling patterns, i.e., to have lower values
when the rectum is only slightly full, and to increase in value
responsive to indications of increased rectal filling.
[0246] It is to be appreciated that preferred stimulation
parameters are described herein by way of illustration and not
limitation, and that the scope of the present invention includes
the use of waveforms comprising, for example, biphasic and/or
monophasic components, a decaying square wave, a sinusoid or
sawtooth waveform, or any other shape known in the art to be
suitable for stimulating muscle or nervous tissue. Generally,
appropriate waveforms and parameters thereof are determined during
an initial test period of device 20, and are updated
intermittently, either in a healthcare facility or automatically
during regular use.
[0247] E. Provision of Power to the Control Unit
[0248] With reference to FIGS. 3 and 4, power is supplied to the
elements of control unit 22 by a battery 56, which may comprise a
primary battery (non-rechargeable) and/or a rechargeable battery.
Alternatively, a super-capacitor, as is known in the art, may be
used to store and provide the electrical power. If a rechargeable
battery or super-capacitor is used, it is preferably recharged via
an inductive coil 58 or antenna, which receives energy by magnetic
induction from an external magnetic field charging source (not
shown) held in proximity to the pelvis of patient 31. The magnetic
field causes a current to flow in coil 58, which is rectified by a
rectifier 60 and furnished to charge battery 56. An optional coil
28, coupled to CPU 52 for the purpose of wireless communications
with device 20, may also be used for charging the battery.
[0249] Preferably, battery 56 comprises a standard battery, such as
a lithium battery, having a nominal output of 3 volts. Most
preferably, pulse generator 54 comprises a DC/DC converter, as is
known in the art, and a capacitor, which is charged by the DC/DC
converter to a constant, stepped-up voltage level regardless of the
precise battery voltage, which may vary between 3.5 and 1.8 volts.
The same DC/DC converter, or another similar device, preferably
supplies power to other circuit components of control unit 22.
[0250] F. External Communication With the Control Unit
[0251] An inductive arrangement using coil 28 is preferably used to
program the CPU, using an external programming device (not shown)
with a suitable antenna. Alternatively, the programming device
generates a modulated magnetic field to communicate with a receiver
inside case 25, which preferably senses the field using a Hall
effect transducer. Such programming may be used, for example, to
set an amplitude or duration of the stimulation waveform applied by
pulse generator 54, or to set a threshold level or other
parameters, according to which the CPU distinguishes between
electromyographic or other signals that are indicative of impending
urge or stress incontinence and those that are not (e.g., those
that indicate voluntary voiding). Such programming may be carried
out by medical personnel or by the patient herself, who can
similarly turn the implanted control unit on and off as desired by
passing a suitable magnet over her pelvis.
[0252] Although the circuit blocks in control unit 22 are shown as
discrete elements, some or all of these blocks are preferably
embodied in a custom or semi-custom integrated circuit device, as
is known in the art.
[0253] G. Utilization of Other Sensors
[0254] FIG. 4 is a schematic block diagram illustrating a muscle
stimulator device 120, in accordance with an alternative embodiment
of the present invention. Device 120 is substantially similar to
device 20, except for features described hereinbelow. Device 120
comprises a control unit 74, which is coupled to electrodes 27 and
29. Electrode 29 also serves as a sensing electrode, furnishing
electromyographic signals via switch 46 to amplifier 48, as
described hereinabove. Alternatively, electrodes 27 and 29 may be
coupled as differential inputs to amplifier 48. Pulse generator 54
applies the stimulation waveforms between electrodes 27 and 29 in a
bipolar mode.
[0255] In addition to or instead of the electromyographic signals
received from electrode 29, CPU 52 preferably receives additional
signals from other physiological sensors, such as an ultrasound
transducer, a pressure sensor 76 and/or an acceleration sensor 78,
or other types of strain and motion measurement devices, as are
known in the art. Pressure sensor 76 is preferably implanted on or
in bladder 36, so as to detect increases in abdominal or
intravesical pressure that may lead to involuntary urine loss.
Similarly, acceleration sensor 78 is preferably implanted so as to
detect bladder motion associated with hypermobility, which is
similarly associated with urine loss. The additional signals from
these sensors are preferably analyzed by the CPU together with the
electromyographic signals in order to improve the accuracy and
reliability of detection of impending incontinence.
[0256] An impedance sensor 79 is preferably used to measure the
tissue impedance between leads 27 and 29, using physiological
impedance measurement techniques known in the art. During long-term
use of device 120 (or other such devices), fibrosis in the area of
the implanted electrodes tends to cause the impedance to increase,
so that the stimulating current for a given applied voltage
decreases. The impedance measured by sensor 79 is used as a
feedback signal instructing CPU 52 to increase the voltage, so that
a generally constant level of stimulation current is
maintained.
[0257] FIG. 10A is a schematic illustration (not to scale) showing
details of a sensor 160 for measuring intravesical pressure, in
accordance with a preferred embodiment of the present invention.
Sensor 160 preferably comprises a pressure-sensitive element such
as a piezoelectric element or a piezoresistive element 162. Element
162 is typically surrounded by silicon oil 166 or a similar liquid,
which, in turn, is contained within a flexible wall 164.
Preferably, element 162 is connected by four leads 168 to control
unit 22. Leads 168 are preferably coupled in a Wheatstone bridge
formation, such that pressure on wall 164 induces a change in
resistance of piezoresistive element 162 which, in turn, is
detected by control unit 22. Typically, control unit 22 applies a
voltage across two of the leads, and senses and amplifies the
voltage developed across the other two leads in order to ascertain
the pressure being applied to sensor 160. In order to increase
battery life, the voltage applied across the leads is preferably
applied in short pulses (e.g., 50 microseconds on, 30 milliseconds
off).
[0258] FIG. 10B is a schematic illustration (not to scale) showing
sensor 160 implanted in the muscle wall of bladder 36, in
accordance with a preferred embodiment of the present invention.
Typically, one or more sensors 160 are implanted in or on the
bladder wall or elsewhere in the abdominal cavity.
[0259] H. Reduction of Power Consumption
[0260] FIG. 5 is a schematic block diagram showing details of
signal processing circuitry 80 for use in device 20 or 120, in
accordance with a preferred embodiment of the present invention. In
order to detect impending incontinence with adequate reliability,
A/D converter 50 optimally samples the EMG signals from the
electrodes at 1000-5000 Hz, and CPU 52 preferably performs a
detailed analysis of the sample stream. Systems for incontinence
control known in the art, operating at sample rates below 1000 Hz,
cannot adequately distinguish between signals that may be
indicative of incontinence and those that are not. For the purpose
of such high-rate sampling, CPU 52 preferably comprises a
low-power, software-programmable processor. If A/D converter 50 and
CPU 52 were to operate continuously, however, battery 56 would
rapidly run down. Therefore, circuitry 80 comprises a low-power,
low-resolution A/D converter 84 and hard-coded processing logic 86,
which operate continuously at a low sampling rate, preferably at
about 100-200 Hz. Input from amplifier 48 to A/D converter 84 is
preferably rectified by a rectifier 82.
[0261] In operation, A/D converter 50 and CPU 52 are normally
maintained in a standby state, in which their power consumption is
negligible. When logic 86, operating at the low sampling rate,
detects EMG signals that may be a precursor to incontinence, it
signals A/D converter 50 to begin sampling at the high rate. In
order not to lose significant data from the brief period before A/D
converter 50 and CPU 52 turn on, signals from A/D converter 84 are
preferably stored in a cyclic (or first-in first-out) queue 88,
such as a delay line. The entire sequence of signal detection and
processing is estimated to take between 5 and 20 ms, up to the
point at which CPU 52 reaches a decision as to whether or not to
actuate pulse generator 54. Pulse generation takes between 1 and 20
ms, with the result that contraction of the pelvic muscles begins
within 15-50 ms of an onset of increased EMG activity indicating
impending urine loss. Thus, urethra 34 is substantially closed off
before any significant amount of urine can leak but.
[0262] As shown in FIG. 5, EMG inputs from electrodes 27 and 29 are
preferably amplified before processing in a dual-differential
configuration, so as to afford enhanced sensitivity and reduced
noise. Electrodes 27 and 29 are coupled to respective differential
preamplifiers 87 and 89, the outputs of which are differentially
amplified by amplifier 48.
[0263] It will be appreciated by persons skilled in the art that
the present invention is not limited to what has been particularly
shown and described hereinabove. Rather, the scope of the present
invention includes both combinations and sub-combinations of the
various features described hereinabove, as well as variations and
modifications thereof that are not in the prior art which would
occur to persons skilled in the art upon reading the foregoing
description.
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