U.S. patent application number 14/093287 was filed with the patent office on 2014-06-05 for apparatus for delivery of pharmaceuticals to the cochlea.
The applicant listed for this patent is Peter Gibson. Invention is credited to Peter Gibson.
Application Number | 20140155811 14/093287 |
Document ID | / |
Family ID | 3825525 |
Filed Date | 2014-06-05 |
United States Patent
Application |
20140155811 |
Kind Code |
A1 |
Gibson; Peter |
June 5, 2014 |
APPARATUS FOR DELIVERY OF PHARMACEUTICALS TO THE COCHLEA
Abstract
An implantable electrode array assembly configured to stimulate
tissue of a recipient, including an elongate member configured to
be inserted into a recipient, wherein at least a portion of the
elongate member includes a bio-active substance.
Inventors: |
Gibson; Peter; (South
Coogee, AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Gibson; Peter |
South Coogee |
|
AU |
|
|
Family ID: |
3825525 |
Appl. No.: |
14/093287 |
Filed: |
November 29, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
13288763 |
Nov 3, 2011 |
|
|
|
14093287 |
|
|
|
|
12535374 |
Aug 4, 2009 |
8401674 |
|
|
13288763 |
|
|
|
|
10416634 |
Nov 10, 2003 |
7571012 |
|
|
PCT/AU01/01479 |
Nov 14, 2001 |
|
|
|
12535374 |
|
|
|
|
Current U.S.
Class: |
604/20 ;
29/825 |
Current CPC
Class: |
Y10T 29/49885 20150115;
A61M 31/00 20130101; A61M 2210/0662 20130101; A61N 1/36038
20170801; Y10T 29/49117 20150115; A61N 1/0541 20130101; A61M 31/002
20130101; A61N 1/32 20130101; A61M 2205/054 20130101; A61M 25/00
20130101; A61M 2210/0668 20130101; A61M 2210/0675 20130101 |
Class at
Publication: |
604/20 ;
29/825 |
International
Class: |
A61N 1/36 20060101
A61N001/36; A61M 31/00 20060101 A61M031/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 14, 2000 |
AU |
PR 1484 |
Claims
1. An implantable electrode array assembly configured to stimulate
tissue of a recipient, comprising: an elongate member configured to
be inserted into a recipient, wherein at least a portion of the
elongate member includes a bio-active substance.
2. The implantable electrode array assembly of claim 1, wherein:
the elongate member is made of a biocompatible material.
3. The implantable electrode array assembly of claim 1, wherein:
the elongate member is impregnated with the bio-active
substance.
4. (canceled)
5. The implantable electrode array assembly of claim 1, wherein:
the implantable electrode array is configured such that the
bio-active substance leaches from the elongate member.
6. The implantable electrode array assembly of claim 1, further
comprising: a plurality of electrodes mounted on the elongate
member.
7. The implantable electrode array assembly of claim 1, wherein:
the elongate member has shape memory.
8. The implantable electrode array assembly of claim 1, wherein:
the elongate member is preformed from a resiliently flexible
material.
9. (canceled)
10. The implantable electrode array assembly of claim 1, wherein:
the elongate member is made of a plastics material with memory.
11. The implantable electrode array assembly of claim 1, wherein:
the elongate member has material memory that returns the elongate
member to a spiral configuration when unrestrained by a separate
component.
12. The implantable electrode array assembly of claim 1, wherein:
the elongate member is coated with a lubricious material.
13. The implantable electrode array assembly of claim 1, wherein:
the elongate member is coated with a material that prevents the
bio-active substance from leaching from the elongate member prior
to implantation of the electrode array assembly into the
recipient.
14. The implantable electrode array assembly of claim 1, wherein:
the coating is a bio-resorbable material.
15. The implantable electrode array assembly of claim 1, wherein
the bio-active substance is selected from the group consisting of a
pharmaceutical agent, an anti-inflammatory substance, an
antibiotic, a steroid, a substance that reduces a resisting neuron
potential of neurons within the cochlea, a substance that promotes
healing, a substance that prevents bleeding and/or prevents
excessive bleeding, a substance that prevents the growth of tissue
and a substance that promotes more efficient neural
stimulation.
16. The implantable electrode array assembly of claim 1, wherein
the bio-active substance is a substance that elicits a change in
the transmembrane potential of a cochlea.
17. A method of manufacturing an implantable electrode array
assembly configured to stimulate tissue of a recipient, comprising:
impregnating at least a portion of an elongate member with a
bio-active substance; and assembling the implantable electrode
array assembly from components including the elongate member.
18.-20. (canceled)
21. An implantable electrode array assembly configured to stimulate
tissue of a recipient, comprising: a means for delivering a
bio-active substance to the recipient, wherein the means for
delivering the bio-active substance is configured to be implanted
in the recipient, and wherein the means is in the form of an
elongate component.
22.-24. (canceled)
25. The implantable electrode array assembly of claim 1, wherein:
the portion of the elongate member including the bio-active
substance forms a surface having a portion at a first location of
the implantable electrode array; at least one electrode is located
on the implantable electrode array at a second location on a
surface of the elongate member; and the second location is located
on a side of the implantable electrode array that is opposite the
first location.
26. (canceled)
27. The implantable electrode array assembly of claim 1, wherein:
the portion of the elongate member including the bio-active
substance is located proximate a first surface, the first surface
having a portion at a first location of the implantable electrode
array; at least one electrode is located on the implantable
electrode array at second location on or proximate a surface of the
elongate member; and the second location is located on a side of
the implantable electrode array that is opposite the first
location.
28. The implantable electrode array assembly of claim 1, wherein:
the elongate member is configured to adopt a curved configuration
after insertion into a cochlea of the recipient to provide
stimulation to the cochlea; the portion of the elongate member that
includes the bio-active substance forms a first surface at which a
first portion of the elongate member is located; the first portion
is located at an outermost convex location of the elongate member
after the elongate member has adopted the curved configuration
after insertion into the cochlea to stimulate the cochlea; and one
or more electrodes are located at a second location that is located
at an innermost concave portion of the elongate member after it has
adopted the curved configuration after insertion into the cochlea
to stimulate the cochlea.
29. The implantable electrode array assembly of claim 1, wherein:
the elongate member is configured to adopt a curved configuration
after insertion into a cochlea of the recipient to provide
stimulation to the cochlea; a first portion of the elongate member
that includes the bio-active substance is located proximate a first
surface of the implantable electrode array the first portion is
located at an outermost convex location of the elongate member
after the elongate member has adopted the curved configuration
after insertion into the cochlea to stimulate the cochlea; and one
or more electrodes are located at a second location that is located
at an innermost concave portion of the elongate member after it has
adopted the curved configuration after insertion into the cochlea
to stimulate the cochlea.
30. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S. patent
application Ser. No. 13/288,763, filed Nov. 3, 2011, which is a
continuation of U.S. patent application Ser. No. 12/535,374, filed
on Aug. 4, 2009, now U.S. Pat. No. 8,401,674, issued on Mar. 19,
2013, which is a continuation of U.S. patent application Ser. No.
10/416,634; filed on Nov. 10, 2003, now U.S. Pat. No. 7,571,012,
issued on Aug. 4, 2009, which is a National Stage Application of
International Application No. PCT/AU01/01479, filed on Nov. 14,
2001, which claims priority to Australian Provisional Application
No. PR 1484, filed on Nov. 14, 2000, the contents of each of these
applications being incorporated herein by reference in their
entirety.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates to an implantable device and,
in particular, to an implantable cochlear electrode assembly.
[0004] 2. Related Art
[0005] Hearing loss, which may be due to many different causes, is
generally of two types, conductive and sensorineural. Of these
types, conductive hearing loss occurs where the normal mechanical
pathways for sound to reach the hair cells in the cochlea are
impeded, for example, by damage to the ossicles. Conductive hearing
loss may often be helped by use of conventional hearing aid
systems, which amplify sound so that acoustic information does
reach the cochlea and the hair cells.
[0006] In many people who are profoundly deaf, however, the reason
for deafness is sensorineural hearing loss. This type of hearing
loss is due to the absence of, or destruction of, the hair cells in
the cochlea which transduce acoustic signals into nerve impulses.
These people are thus unable to derive suitable benefit from
conventional hearing aid systems, because there is damage to or
absence of the mechanism for nerve impulses to be generated from
sound in the normal manner.
[0007] It is for this purpose that cochlear implant systems have
been developed. Such systems bypass the hair cells in the cochlea
and directly deliver electrical stimulation to the auditory nerve
fibres, thereby allowing the brain to perceive a hearing sensation
resembling the natural hearing sensation normally delivered to the
auditory nerve. U.S. Pat. No. 4,532,930, the contents of which are
incorporated herein by reference, provides a description of one
type of traditional cochlear implant system.
[0008] Cochlear implant systems have typically consisted of two key
components, namely an external component commonly referred to as a
processor unit, and an implanted internal component commonly
referred to as a stimulator/receiver unit. Traditionally, both of
these components have cooperated together to provide the sound
sensation to an implantee.
[0009] The external component has traditionally consisted of a
microphone for detecting sounds, such as speech and environmental
sounds, a speech processor that converts the detected sounds and
particularly speech into a coded signal, a power source such as a
battery, and an external antenna transmitter coil.
[0010] The coded signal output by the speech processor is
transmitted transcutaneously to the implanted stimulator/receiver
unit situated within a recess of the temporal bone of the
implantee. This transcutaneous transmission occurs through use of
an inductive coupling provided between the external antenna
transmitter coil which is positioned to communicate with an
implanted antenna receiver coil provided with the
stimulator/receiver unit. This communication serves two essential
purposes, firstly to transcutaneously transmit the coded sound
signal and secondly to provide power to the implanted
stimulator/receiver unit. Conventionally, this link has been in the
form of a radio frequency (RF) link, but other such links have been
proposed and implemented with varying degrees of success.
[0011] The implanted stimulator/receiver unit typically includes
the antenna receiver coil that receives the coded signal and power
from the external processor component, and a stimulator that
processes the coded signal and outputs a stimulation signal to an
intracochlea electrode assembly which applies the electrical
stimulation directly to the auditory nerve producing a hearing
sensation corresponding to the original detected sound.
[0012] The external componentry of the cochlear implant has been
traditionally carried on the body of the implantee, such as in a
pocket of the implantee's clothing, a belt pouch or in a harness,
while the microphone has been mounted on a clip mounted behind the
ear or on a clothing lapel of the implantee.
[0013] More recently, due in the main to improvements in
technology, the physical dimensions of the speech processor have
been able to be reduced allowing for the external componentry to be
housed in a small unit capable of being worn behind the ear of the
implantee. This unit has allowed the microphone, power unit and the
speech processor to be housed in a single unit capable of being
discretely worn behind the ear, with the external transmitter coil
still positioned on the side of the user's head to allow for the
transmission of the coded sound signal from the speech processor
and power to the implanted stimulator unit. It is also considered
that with continued improvements in technology, it may become
possible to provide a system whereby all components of the system
are implanted inside the head of the implantee resulting in a
system that is completely invisible and does not require any
external components to operate, at least for a portion of the
time.
[0014] Together with improvements in available technology much
research has been undertaken in the area of understanding the way
sound is naturally processed by the human auditory system. With
such an increased understanding of how the cochlea naturally
processes sounds of varying frequency and magnitude, there is a
need to provide an improved cochlear implant system that delivers
electrical stimulation to the auditory nerve in a way that takes
into account the natural characteristics of the cochlea.
[0015] It is known in the art that the cochlea is tonotopically
mapped. In other words, the cochlea can be partitioned into
regions, with each region being responsive to signals in a
particular frequency range. This property of the cochlea is
exploited by providing the electrode assembly with an array of
electrodes, each electrode being arranged and constructed to
deliver a cochlea stimulating signal within a preselected frequency
range to the appropriate cochlea region. The electrical currents
and electric fields from each electrode stimulate the cilia
disposed on the modiola of the cochlea. Several electrodes may be
active simultaneously.
[0016] It has been found that in order for these electrodes to be
effective, the magnitude of the currents flowing from these
electrodes and the intensity of the corresponding electric fields,
are a function of the distance between the electrodes and the
modiola. If this distance is relatively great, the threshold
current magnitude must be larger than if the distance is relatively
small. Moreover, the current from each electrode may flow in all
directions, and the electrical fields corresponding to adjacent
electrodes may overlap, thereby causing cross-electrode
interference. In order to reduce the threshold stimulation
amplitude and to eliminate cross-electrode interference, it is
advisable to keep the distance between the electrode array and the
modiola as small as possible. This is best accomplished by
providing the electrode array in the shape which generally follows
the shape of the modiola. Also, this way the delivery of the
electrical stimulation to the auditory nerve is most effective as
the electrode contacts are as close to the auditory nerves that are
particularly responsive to selected pitches of sound waves.
[0017] In order to achieve this electrode array position close to
the inside wall of the cochlea, the electrode needs to be designed
in such a way that it assumes this position upon or immediately
following insertion into the cochlea. This is a challenge as the
array needs to be shaped such that it assumes a curved shape to
conform with the shape of the modiola and must also be shaped such
that the insertion process causes minimal trauma to the sensitive
structures of the cochlea. In this sense it has been found to be
desirable for the electrode array be generally straight during the
insertion procedure.
[0018] Several procedures have been adopted to provide an electrode
assembly that is relatively straightforward to insert while
adopting a curved configuration following insertion in the cochlea.
In one case, a platinum wire stylet is used to hold a pre-curved
electrode array in a generally straight configuration up until
insertion. Following insertion, the platinum stylet is withdrawn
allowing the array to return to its pre-curved configuration.
[0019] In developing electrode array designs, it is of great
importance that the design be constructed to minimise potential
damage to sensitive structures in the cochlea upon insertion and
placement of the array. While electrode arrays are preferably
designed to minimise such damage, the cochlea does suffer a degree
of trauma due to the insertion process.
[0020] Any discussion of documents, acts, materials, devices,
articles or the like which has been included in the present
specification is solely for the purpose of providing a context for
the present invention. It is not to be taken as an admission that
any or all of these matters form part of the prior art base or were
common general knowledge in the field relevant to the present
invention as it existed in Australia before the priority date of
each claim of this application.
SUMMARY
[0021] Throughout this specification the word "comprise", or
variations such as "comprises" or "comprising", will be understood
to imply the inclusion of a stated element, integer or step, or
group of elements, integers or steps, but not the exclusion of any
other element, integer or step, or group of elements, integers or
steps.
[0022] It is a preferred feature of the present invention to
provide an electrode assembly that is adapted to assist the cochlea
in its recovery from trauma following the insertion of an electrode
assembly therein. The present invention is equally applicable to
conventional electrode assemblies and electrode assemblies which
are designed to conform with the inner wall of the cochlea.
[0023] According to a first aspect, the present invention is an
implantable tissue-stimulating device comprising: a resiliently
flexible elongate member having a plurality of electrodes mounted
thereon; and a bio-active substance delivery means adapted to
deliver at least one bio-active substance to the implantee
following implantation of the device.
[0024] In a preferred embodiment of this invention, the device is a
cochlear implant electrode assembly.
[0025] In one embodiment, the substance delivery means can comprise
at least a portion of the elongate member that has been impregnated
with a bio-active substance that can leach therefrom following
implantation.
[0026] In a further embodiment, the elongate member preferably has
a first end that is firstly inserted into the implantee.
[0027] In another embodiment, the substance delivery means can
include a lumen extending through the elongate member for at least
a portion of its length. The lumen can be cylindrical or have any
other suitable cross-sectional shape. In one embodiment, the lumen
extends through the elongate member for a substantial portion of
its length. In a further embodiment, the lumen extends from an
opening distal the first end to a position that is at or adjacent
the first end. The distal opening of the lumen preferably can be
closed by a closure means adapted to seal the opening of the
lumen.
[0028] The closure means can comprise a plug adapted to be inserted
into the lumen and to form a seal therewith. The plug can have a
frusto-conical outer wall adapted to seal with the wall of the
lumen on insertion. The plug in this embodiment can be formed from
a resiliently flexible material such as silicone or polyurethane.
Alternatively, the plug could be of any suitable shape and could
also be formed from a stiff plastic, such as
polytetrafluoroethylene (PTFE), or a metal, such as platinum or
stainless steel.
[0029] In another embodiment, the closure means can comprise a cap
adapted to seal the distal opening of the lumen. In one embodiment,
the cap can have a top adapted to seal the opening and a skirt
depending therefrom. The skirt can have an engagement means formed
on an outer surface thereof adapted to engage with the inner
surface of the lumen on mounting of the cap to the lumen. In this
embodiment, the inner surface of the lumen can have an engagement
means complementary to that on the outer surface of the skirt of
the cap. The engagement means on the skirt can comprise a screw
thread adapted to engage with a corresponding screw thread on the
inner cylindrical surface of the lumen.
[0030] The lumen in the elongate member can act as a reservoir for
a bio-active substance within the elongate member. In one
embodiment, the bio-active substance in the reservoir can leach
from the lumen into the outer surface of the member that is
preferably close to the desired site of action for the bio-active
substance. In another embodiment, the elongate member can have one
or more substance egress means whereby the substance can move out
of the lumen and the elongate member to a position that is
preferably close to the desired site of action for the bio-active
substance.
[0031] Where the bio-active substance is carried in or comprises a
fluid, each substance egress means preferably comprises a fluid
egress means.
[0032] Each fluid egress means preferably has a valve means that
allows fluid to exit the lumen but prevents, or at least
substantially prevents, fluid flow from external the elongate
member back into the lumen within the elongate member.
[0033] In a further embodiment, the distal opening of the lumen can
be in fluid communication with an additional reservoir for the
bio-active substance that is external to the elongate member. A
pumping means, such as an osmotic pump, can transfer the bio-active
substance from the additional reservoir into the lumen of the
elongate member for subsequent delivery to the appropriate site of
action.
[0034] It is also envisaged that the bio-active substance can be
captured in the form of a solid pellet 55. In one embodiment shown
in FIG. 5, the solid pellet 55 can be formed by impregnating the
bio-active substance in a ceramic or a polymer pellet that has a
predetermined rate of release of the bioactive substance. This
solid pellet 55 can then be stored in the lumen reservoir or in an
external reservoir connectable to the lumen.
[0035] In one embodiment, the bioactive substance can comprise a
steroid. In another embodiment, the bioactive substance can perform
a function of reducing the resting neuron potential of neurons
within the cochlea. The use of such substances can result in less
energy being required to excite the neurons and cause
stimulation.
[0036] In a further embodiment, the elongate member can have a
first configuration selected to allow said member to be inserted
into an implantee's body, such as the cochlea, and a second
configuration wherein said elongate member is adapted to apply a
preselected tissue stimulation with the electrodes. In a further
embodiment, the elongate member can have at least one intermediate
configuration between said first and second configurations.
[0037] In a still further embodiment shown in FIG. 5, at least a
portion of the outer surface can have a coating of lubricious
material 57. In a further embodiment, a substantial portion of the
outer surface can have a coating of the lubricious material 57. In
a still further embodiment, the entire outer surface of the
elongate member can have a coating of the lubricious material
57.
[0038] The lubricious material 57 preferably becomes lubricious on
being brought into contact with a fluid, such as a saline solution.
Still further, the coating 57 preferably becomes lubricious on
being brought into contact with a body fluid, such as cochlear
fluid.
[0039] In one embodiment, the lubricious material 57 is selected
from the group comprising polyacrylic acid (PAA), polyvinyl alcohol
(PVA), polylactic acid (PLA) and polyglycolic acid (PGA). It is
envisaged that other similar materials could also be used. It is
envisaged that the lubricious material 57 can also be impregnated
with the bio-active substance allowing the coating to perform a
dual role. The rate of delivery of the bio-active substance can be
programmed by design of the coating structure.
[0040] In yet another embodiment, the device can include a
stiffening element made of a second material relatively stiffer
than the resiliently flexible material of the elongate member. The
stiffening element can be adapted to bias the elongate member into
the first configuration.
[0041] In a still further embodiment, the device can include a
stiffening sheath that envelops said elongate member and which is
made of a material that is relatively stiffer than the resiliently
flexible material of the elongate member. The stiffening sheath can
be adapted to bias the elongate member into the first
configuration. In one embodiment, the stiffening sheath can be
overlaid by the coating of lubricious material.
[0042] Where both the stiffening element and stiffening sheath are
present in the device, the element and sheath can be adapted in
combination to bias said elongate member into said first
configuration. In this embodiment, if either the stiffening element
or the stiffening sheath is removed or deactivated, the elongate
member can adopt said at least one intermediate configuration. In
this embodiment, the stiffening sheath can be formed of the same
material or a different material to that of the stiffening element.
In either case, the stiffening sheath can be relatively more
stiffer or relatively less stiffer than the stiffening element.
[0043] In a preferred embodiment, the second configuration of the
elongate configuration when in the second configuration.
[0044] The elongate member is preferably preformed from a plastics
material with memory and is preformed to the second
configuration.
[0045] In a preferred embodiment, the first configuration is
preferably substantially straight. More preferably, the first
configuration is straight.
[0046] In a preferred embodiment, the elongate member is formed
from a suitable biocompatible material. In one embodiment, the
material can be a silicone, such as Silastic MDX 4-4210. In another
embodiment, the elongate member can be formed from a polyurethane
or similar material.
[0047] In one embodiment, the stiffening element is formed of a
bioresorbable material which softens or dissolves on exposure to a
fluid. The stiffening element can soften or dissolve on exposure to
a saline solution or a body fluid of the implantee, such as
cochlear fluid.
[0048] In a further embodiment, the bioresorbable material of the
stiffening element is selected from the group comprising
polyacrylic acid (PAA), polyvinyl alcohol (PVA), polylactic acid
(PLA) and polyglycolic acid (PGA). It is envisaged that other
similar materials could also be used. It is envisaged that the
bioresorbable material of the stiffening element can also be
impregnated with one or more of the bio-active substances allowing
the stiffening element to perform a dual role. The rate of delivery
of the bioactive substance can be determined by the structural
design of, or the materials used in, the stiffening element
structure.
[0049] In another embodiment, the stiffening element can be formed
from a non-bioresorbable material. In this embodiment, the
stiffening element can comprise a metallic stylet, or a stylet-like
element formed from any other suitable stiffening material,
extending through a lumen in the elongate member. In one
embodiment, the wire can be formed from a biocompatible metal, a
biocompatible metallic alloy or a biocompatible relatively stiff
plastic. In a preferred embodiment, a metal stylet can be formed
from platinum.
[0050] In a still further embodiment, the stiffening element can be
formed from a shape memory or heat sensitive material. For example,
the stiffening element can be formed from a bimetallic element
(such as nickel/titanium) and shaped to take a straight or
substantially straight configuration at room temperature but bend
into another shape on exposure to body temperature (eg. about
37.degree. C.).
[0051] The lumen for the stylet can be the same lumen as utilised
in one embodiment of the substance delivery means defined above. In
another embodiment, the lumen can be a different lumen to that
utilised as part of the substance delivery means defined above. The
lumen for the stylet can be cylindrical and also can have an
opening formed therein. In the case of a metal stylet, the stylet
can extend out of the opening allowing the stylet to be manipulated
and removed from the lumen during or following insertion of the
device. In the case of a bioresorbable stiffening element, the
opening can act as a fluid ingress means allowing body fluids to
enter the lumen on insertion of the device into an implantee.
[0052] The stiffening sheath, if present, can be formed of a
bioresorbable material which dissolves or softens on exposure to a
fluid. The stiffening sheath can dissolve or soften on exposure to
a saline solution or a body fluid of the implantee, such as
cochlear fluid and in doing so also release one or more bio-active
substances impregnated therein.
[0053] In a further embodiment, the bioresorbable material of the
stiffening sheath is selected from the group comprising polyacrylic
acid (PAA), polyvinyl alcohol (PVA), polylactic acid (PLA) and
polyglycolic acid (PGA). It is envisaged that other suitable
materials could also be used. It is envisaged that the
bioresorbable element of the stiffening sheath can also be
impregnated with one or more bio-active substances allowing the
stiffening sheath to perform a dual role. The rate of delivery of
the bio-active substance can be set by the structural design of, or
the materials used in, the sheath structure.
[0054] The device can include an additional layer surrounding the
stiffening sheath. The additional layer can have a first rate of
fluid ingress therethrough and have at least one fluid ingress
means formed therein, the rate of fluid ingress through the fluid
ingress means being greater than the first rate of fluid ingress
through the additional layer. In this embodiment, the coating of
lubricious material can be coated on the outside of the additional
layer.
[0055] The fluid ingress means can comprise one or more openings in
the additional layer. The openings can be closable. The openings
can comprise slits in the additional layer. The slits can be formed
to allow substantially the same or the same rate of ingress of
fluid through the additional layer. In another embodiment, at least
one slit can allow a different rate of progress of fluid through
the additional layer compared to the other slits. In one
embodiment, the slits can be sealable with a bioresorbable
material. The bioresorbable material preferably softens and/or
dissolves on exposure to a fluid, such as cochlear fluid, to allow
ingress of the fluid into the elongate member. In this embodiment,
the slits can be sealed with the same or a different quantity
and/or the same or different thicknesses of bioresorbable material.
Variations in thickness and/or quantity of the bioresorbable
material provide a means of varying the rate of ultimate
dissolution of the stiffening element of the device, if present,
and/or the rate of elution of said at least one bioactive
substance.
[0056] In another embodiment, the slits can be designed so that
when the electrode array is in a straight configuration the slits
are closed, preventing the ingress of fluid therethrough. The
closure of the slits can be formed by the material of the outer
wall, such as silicone, being under compression. When the electrode
array is inserted into the cochlea and begins to assume a curved
configuration, the slits become open allowing the ingress of fluid
therethrough, due in the main to the silicone in the outer wall
being released from the state of compression. Such a design allows
greater control of the rate of fluid ingress and subsequent
dissolution of the stiffening element of the device and/or the
elution of said at least one bioactive substance.
[0057] The stiffening sheath, if present, can be formed from a
shape memory or heat sensitive material. For example, the
stiffening sheath can be formed from a bimetallic or alloy filament
(such as nickel/titanium) and shaped to take and maintain the
straight or substantially straight configuration of the elongate
member at room temperature but bend it into another shape once it
is exposed to body temperature.
[0058] In one embodiment, while both the stiffening element and the
stiffening sheath are in position within the device, it will retain
the first configuration, which as discussed is preferably straight.
If the stiffening sheath is removed or softened, whether it is by
dissolution or otherwise, the remaining stiffening element can have
insufficient strength to retain the elongate member in its first
configuration. It is preferred that the elongate member, on removal
or softening of the stiffening sheath, will adopt an intermediate
configuration in which the elongate member has at least some
curvature.
[0059] The present invention provides a surgeon with a cochlear
implant electrode array that can assist with the delivery of one or
more bio-active substances to the implantation site following its
implantation. The substances that can be delivered by the present
device include substances that are adapted to promote healing,
substances that prevent bleeding or at least excessive bleeding,
and also substances that prevent the growth of tissue, including
scar tissue, in the cochlea following implantation. Pharmaceutical
compounds such as anti-inflammatories and antibiotics can also be
delivered by the present device.
[0060] It is also envisaged that substances that assist in reducing
the resting potential of the surrounding neurons can also be
delivered by the present invention. It should be appreciated that
during neural stimulation the neurons propagate an action potential
through the response of transmembrane ion channels to local
electrical fields. By delivering a substance that elicits a change
in the transmembrane potential, the resting neural membrane
potential can be moved towards the activation potential resulting
in a lowering of the energy required to be delivered to activate
the neuron. This also has the potential to reduce the power
required by the stimulation device as well as increase the
specificity of the electrical stimulation and restore the
stochastic response of the neurons.
[0061] In one embodiment, and where the elongate member is
impregnated with a bio-active substance, the device can be formed
by a method that includes a step of impregnating the elongate
member with the bio-active substance prior to implantation.
Impregnation may be achieved by soaling the elongate member in a
solution that constitutes or includes the bio-active substance for
a period of time. The degree of impregnation can be controlled by
the period of time of soaking of the elongate member. It is
anticipated that the degree of impregnation will impact on the rate
of substance delivery by the device following implantation.
[0062] In another embodiment, and where the elongate member
includes a lumen acting as a reservoir for a bio-active substance,
the lumen can be filled with the bio-active substance prior to
implantation. In one embodiment, the lumen can be filled during
manufacture and/or packaging of the elongate member. In another
embodiment, the lumen can be filled, such as by the surgeon, just
prior to implantation. The substance egress means preferably does
not allow the bio-active substance to pass from the lumen until the
device is ready for implantation or after implantation. In one
embodiment, the substance egress means could be activated by the
surgeon just prior to its insertion into the implantee. In another
embodiment, the substance egress means may be coated with a layer
of bioresorbable material that softens and/or dissolves on exposure
to a fluid, such as cochlear fluid. Following its dissolution, the
bio-active substance is free to pass through the substance egress
means.
[0063] The device can be adapted to only provide delivery of a
bio-active substance to the implantation site for a particular
period following implantation. This period may comprise any period
of time from a few hours or days to a few weeks or even months. In
another embodiment, the device can be used as a means of delivery
of bio-active substances to the implantee well beyond the time of
implantation. For example, the additional reservoir can be
periodically filled with a bio-active substance to ensure continued
supply of the bio-active substance to the implantation site. The
additional reservoir, in this case, may be positioned beneath but
adjacent the surface of the skin of the implantee thereby allowing
the reservoir to be filled by a syringe and needle assembly that
injects the bio-active substance into the additional reservoir.
[0064] Once implanted, the electrodes can receive stimulation
signals from a stimulator means. The stimulator means is preferably
electrically connected to the elongate member by way of an
electrical lead. The lead can include the one or more wires
extending from each electrode of the array mounted on the elongate
member.
[0065] In one embodiment, the lead can extend from the elongate
member to a stimulator means or at least the housing thereof. In
one embodiment, the lead is continuous with no electrical
connectors, at least external the housing of the stimulator means,
required to connect the wires extending from the electrodes to the
stimulator means. One advantage of this arrangement is that there
is no requirement for the surgeon implanting the device to make the
necessary electrical connection between the wires extending from
the electrodes and the stimulator means.
[0066] The stimulator means is preferably positioned within a
housing that is implantable within the implantee. The housing for
the stimulator means is preferably implantable within the bony well
in the bone behind the ear posterior to the mastoid.
[0067] When implantable, the housing preferably contains, in
addition to the stimulator means, a receiver means. The receiver
means is preferably adapted to receive signals from a controller
means. The controller means is, in use, preferably mounted external
to the body of the implantee such that the signals are transmitted
transcutaneously through the implantee.
[0068] Signals can preferably travel from the controller means to
the receiver means and vice versa. The receiver means can include a
receiver coil adapted to receive radio frequency (RF) signals from
a corresponding transmitter coil worn externally of the body. The
radio frequency signals can comprise frequency modulated (FM)
signals. While described as a receiver coil, the receiver coil can
preferably transmit signals to the transmitter coil which receives
the signals.
[0069] The transmitter coil is preferably held in position adjacent
the implanted location of the receiver coil by way of respective
attractive magnets mounted centrally in, or at some other position
relative to, the coils.
[0070] The external controller can comprise a speech processor
adapted to receive signals output by a microphone. During use, the
microphone is preferably worn on the pinna of the implantee,
however, other suitable locations can be envisaged, such as a lapel
of the implantee's clothing. The speech processor encodes the sound
detected by the microphone into a sequence of electrical stimuli
following given algorithms, such as algorithms already developed
for cochlear implant systems. The encoded sequence is transferred
to the implanted stimulator/receiver means using the transmitter
and receiver coils. The implanted stimulator/receiver means
demodulates the FM signals and allocates the electrical pulses to
the appropriate attached electrode by an algorithm which is
consistent with the chosen speech coding strategy.
[0071] The external controller further comprises a power supply.
The power supply can comprise one or more rechargeable batteries.
The transmitter and receiver coils are used to provide power via
transcutaneous induction to the implanted stimulator/receiver means
and the electrode array.
[0072] While the implant system can rely on external componentry,
in another embodiment, the controller means, including the
microphone, speech processor and power supply can also be
implantable. In this embodiment, the controller means can be
contained within a hermetically sealed housing or the housing used
for the stimulator means.
BRIEF DESCRIPTION OF THE DRAWINGS
[0073] By way of example only, a preferred embodiment of the
invention is now described with reference to the accompanying
drawings, in which:
[0074] FIG. 1 is a pictorial representation of a prior art cochlear
implant system;
[0075] FIG. 2 is a simplified cross-sectional view of one
embodiment of an electrode assembly according to the present
invention ready for insertion into a cochlea; and
[0076] FIG. 3 is a simplified part-sectional, part side elevational
view of the electrode assembly depicted following insertion in the
cochlea;
[0077] FIG. 4 is a simplified cross-sectional view of an electrode
assembly in accordance with another embodiment of the present
invention;
[0078] FIG. 5 is a simplified cross-sectional view of an electrode
assembly in accordance with a still further embodiment of the
present invention; and
[0079] FIGS. 6A and 6B are simplified cross-sectional views of an
electrode assembly in accordance with other embodiments of the
present invention.
DETAILED DESCRIPTION
[0080] Before describing the features of the present invention, it
is appropriate to briefly describe the construction of one type of
known cochlear implant system with reference to FIG. 1.
[0081] Known cochlear implants typically consist of two main
components, an external component including a speech processor 9,
and an internal component including an implanted receiver and
stimulator unit 2. The external component includes a microphone 7.
The speech processor 9 is, in this illustration, constructed and
arranged so that it can fit behind the outer ear 1. Alternative
versions may be worn on the body. Attached to the speech processor
9 is a transmitter coil 4 which transmits electrical signals to the
implanted unit 2 via a radio frequency (RF) link.
[0082] The implanted component includes a receiver coil 3 for
receiving power and data from the transmitter coil 4. A cable 41
extends from the implanted receiver and stimulator unit 2 to the
cochlea 30 and terminates in an electrode array 20. The signals
thus received are applied by the array 20 to the basilar membrane 8
and the nerve cells within the cochlea 30 thereby stimulating an
auditory nerve 5. The operation of such a device is described, for
example, in U.S. Pat. No. 4,532,930.
[0083] One embodiment of a cochlear implant electrode assembly
according to the present invention is depicted generally as 10 in
FIGS. 2 and 3.
[0084] The depicted electrode assembly 10 has an electrical lead
extending back to a stimulator/receiver housing, such as the
stimulator unit 2 depicted in FIG. 1. In considering this
invention, it is to be understood that each electrode 12 may have
one or more wires (not depicted) electrically connected thereto and
extending from each respective electrode 19 back through the lead
to the stimulator/receiver.
[0085] The assembly 10 comprises an elongate electrode carrier
member 11 having a plurality of electrodes 12 mounted thereon. For
the purposes of clarity, the electrodes 12 depicted in FIG. 1 are
not necessarily shown to scale. A larger number of electrodes than
that depicted in FIG. 2 can also be envisaged. The electrodes 12
are not depicted in FIG. 3 for reasons of clarity.
[0086] The depicted elongate member 11 is preformed from a
resiliently flexible silicone with memory and is preformed to a
curved configuration suitable for insertion in the scala tympani 31
of a human cochlea 30. While an assembly that normally adopts a
curved configuration when in a relaxed condition is depicted in the
drawings, it will be appreciated that the present invention also
could be utilised with respect to assemblies that are normally
straight when in a relaxed condition.
[0087] The elongate member 11 has a first end 13 that is firstly
inserted into the cochlea 30 upon insertion of the assembly 10.
[0088] As depicted in FIG. 2, there is disposed within a lumen 14,
prior to insertion of the assembly 10 into the cochlea 30, a
substantially straight platinum stylet 15. In the depicted
embodiment, the stylet 15 has a stiffness that is sufficient to
retain the silicone elongate member 11 in a straight configuration.
The stylet could be constructed so as to have a stiffness that was
insufficient alone to retain the elongate member 11 in a straight
configuration. In this case, the elongate member could have a
stiffening sheath 18 that at lest partially envelops the elongate
member 11. The stiffening sheath 18 could be formed of a
bioresorbable material which prior to implantation assists the
platinum stylet in maintaining the elongate member 11 in the
straight configuration.
[0089] While a platinum stylet is depicted, a bioresorbable
stylet-like member formed from a bioresorbable material, such as
polyacrylic acid (PAA), that is also impregnated with a bio-active
substance and which is adapted to dissolve or soften on exposure to
cochlear fluids, could be utilised with appropriate modification to
the elongate carrier member 11. A stiffening polymer stylet could
also be utilised which could be impregnated with a bio-active
substance. Such a stylet would soften quickly, but not dissolve
quickly, with its very slow dissolution rate allowing the drug to
effectively elute to the body. Equally, whilst a substantially
cylindrical lumen is depicted, the lumen 14 could indeed be any
shape necessary to perform the function. Again, the PAA stylet-like
member in this invention can have a stiffness that is either
sufficient or insufficient to retain the silicone elongate member
11 in a straight configuration as depicted in FIG. 2. It will be
appreciated that a bioresorbable stylet-like member could be formed
from other suitable bioresorbable materials. A stylet-like member
made from a shape memory or heat sensitive material could also be
utilised instead of stylet 15.
[0090] In the depicted embodiment, the elongate member 11 is
adapted to also act as a system for delivery of one or more
pharmaceutical or bioactive substances to the cochlea 30. In the
depicted embodiment, this system is provided by an additional lumen
21 that acts as a reservoir for a fluid 23 constituting or
including the one or more pharmaceutical or bioactive substances.
The lumen 21 is pre-filled with the pharmaceutical or bioactive
substances during manufacture and then sealed by the plug closure
22.
[0091] Provided at the first end 13 of the member 11 is a fluid
egress means comprising a valve 24 in the form of a slit formed in
the structure of the elongate member 11. Other embodiments with
more than one slit 24 can be envisaged. The slit 24 is adapted to
allow fluid 23 within the lumen 21 to exit the lumen 21 but
prevents fluid flow from external the member 11 back into the lumen
21. To prevent flow of fluid through the slit 24 prior to
implantation, the slit is covered with a layer 25 of bioresorbable
PAA. Other suitable bioresorbable materials could be envisaged and
the material could also be impregnated with the pharmaceutical
substance. While only depicted as covering the slit 24, the layer
25 could coat a greater portion or the entire surface of the
elongate member 11.
[0092] On insertion of the elongate member 11 into the scala
tympani 31, the cochlear fluid commences to soften and dissolve the
layer 25 of PAA. In addition to lubricating the first end 13, the
dissolution of the layer 25 allows the fluid 23 to commence to flow
from the lumen 21 into the scala tympani 31.
[0093] It is also possible that the pharmaceutical or bioactive
substance 23 could be released from the lumen 21 by way of a
mechanical means. Such a means may include pushing the stylet 15
through the slit 24 at the end of the assembly 10 to break the seal
just prior to insertion. As shown in FIGS. 6A and 6B, another
method of releasing the pharmaceutical substance would be to
include a suture 26 down the lumen 21 and through the seal 25. The
suture 26 could then be pulled in an action similar to a "rip-cord"
to open the end of the assembly 10.
[0094] In the embodiments shown in FIG. 4, lumen 21 is in fluid
communication with an additional reservoir 45 for fluid 23.
Additional reservoir 45 can be placed under the skin of the
implantee and be Tillable by a needle and syringe assembly when
required. A pump 47, such as an osmotic pump, can be used to
transfer fluid from additional reservoir 45 to lumen 21.
[0095] While depicted with a lumen 21, it can also be envisaged
that the elongate member 11 could be impregnated with a
pharmaceutical agent or other bioactive substance prior to
implantation. The pharmaceutical agent or bioactive substance would
then be free to leach from the elongate member 11 following
insertion. In this embodiment, it can be envisaged that a layer of
bioresorbable PAA material may coat the entire impregnated portion
of the elongate member 11 so ensuring that the pharmaceutical agent
or bioactive substance does not leach from the elongate member 11
prior to implantation.
[0096] While the elongate member 11 is manufactured with a
preformed curved configuration, the depicted assembly 10 is
typically delivered to a surgeon in a sterile package with the
stylet 15 and pharmaceutical fluid 23 in place (as depicted in FIG.
2).
[0097] On removal from the package and insertion into the scala
tympani 31 of the cochlea 30, the cochlear fluids commence to
dissolve and soften the layer 25.
[0098] As the elongate member 11 is inserted into the scala tympani
31 of the cochlea 30, the surgeon can commence to withdraw the
stylet 15 from the lumen 14 through opening 17. On withdrawal of
the stylet 15, the elongate member 11 is free to adopt the spiral
configuration depicted in FIG. 3 with the electrodes 12 facing the
modiola within the cochlea 30 so that they are positioned as close
as possible to the spiral ganglia thereof.
[0099] The provision of a system for delivering a pharmaceutical
substance that promotes healing and/or more efficient neural
stimulation while preventing the formation of substantial scar
tissue in the cochlea, enhances the likelihood of successful
long-term placement of the assembly 10 in the cochlea and
subsequent successful use of the cochlear implant by the
implantee.
[0100] While the preferred embodiment of the invention has been
described in conjunction with a cochlear implant, it is to be
understood that the present invention has wider application to
other implantable electrodes, such as electrodes used with
pacemakers.
[0101] It will be appreciated by persons skilled in the art that
numerous variations and/or modifications may be made to the
invention as shown in the specific embodiments without departing
from the spirit or scope of the invention as broadly described. The
present embodiments are, therefore, to be considered in all
respects as illustrative and not restrictive.
[0102] All documents, patents, journal articles and other materials
cited in the present application are hereby incorporated by
reference.
[0103] It is to be understood that the detailed description and
specific examples, while indicating embodiments of the present
invention, are given by way of illustration and not limitation.
Many changes and modifications within the scope of the present
invention may be made without departing from the spirit thereof,
and the invention includes all such modifications.
* * * * *