Securing an implanted medical device in a patient

An apparatus and method for implanting and securing an implanted medical device in a recipient. The implantable medical device of the generally includes a stimulating lead assembly that comprises an elongate carrier member having at least one stimulating element positioned thereon. The stimulating lead assembly further has an expandable portion thereon configured to be inserted into said reference structure in a first dimension, expand to a second dimension, and interact with a portion of the reference structure to help longitudinally secure the carrier member in the recipient.

BACKGROUND

1. Field of the Invention

The present invention relates to an implantable device and, in particular, to securing an implantable tissue-stimulating device in a recipient.

2. Related Art

Hearing loss, which may be due to many different causes, is generally of two types, conductive and sensorineural. In some cases, a person may have hearing loss of both types. Conductive hearing loss occurs when 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 is often addressed with conventional hearing aids which amplify sound so that acoustic information can reach the cochlea.

In many people who are profoundly deaf, however, the reason for their deafness is sensorineural hearing loss. Sensorineural hearing loss occurs when there is damage to the inner ear or to the nerve pathways from the inner ear to the brain. Those suffering from sensorineural hearing loss are thus unable to derive suitable benefit from conventional hearing aids. As a result, hearing prostheses that deliver electrical stimulation to nerve cells of the recipient's auditory system have been developed to provide persons having sensorineural hearing loss with the ability to perceive sound. Such stimulating hearing prostheses include, for example, auditory brain stimulators and cochlear prostheses (commonly referred to as cochlear prosthetic devices, cochlear implants, cochlear devices, and the like; simply “cochlear implants” herein.) As used herein, the recipient's auditory system includes all sensory system components that may be used to perceive a sound signal, such as hearing sensation receptors, neural pathways, including the auditory nerve and spiral ganglion, and regions of the brain used to sense sounds.

Most sensorineural hearing loss is due to the absence or destruction of the cochlea hair cells which transduce acoustic signals into nerve impulses. It is for this purpose that cochlear implants have been developed. Cochlear implants use direct electrical stimulation of auditory nerve cells to bypass absent or defective hair cells that normally transduce acoustic vibrations into neural activity. Such devices generally use an array of electrode contacts implanted into the scala tympani of the cochlea so that the electrodes may differentially activate auditory neurons that normally encode differential pitches of sound.

Auditory brain stimulators are used to treat a smaller number of recipients with bilateral degeneration of the auditory nerve. For such recipients, the auditory brain stimulator provides stimulation of the cochlear nucleus in the brainstem.

SUMMARY

In one aspect of the present invention, there is provided a stimulating lead assembly for implantation into a recipient through an opening in a reference structure in the recipient, comprising: an carrier member, having a proximal and a distal end and at least one stimulation element disposed along said carrier member; and an expandable portion being expandable from a first dimension to a second dimension, and configured to interact with the reference structure when said carrier member is implanted in the recipient and expanded to said second dimension.

In another aspect of the present invention, there is provided a method of implanting a stimulating medical device, comprising: preparing an appropriately configured opening in a reference structure of a recipient for implantation of an stimulating lead assembly comprising a carrier member and expandable portion; inserting said carrier member through said opening in the recipient; and expanding said expandable portion from a first dimension to a second dimension to interact with a portion of the reference structure to longitudinally secure said carrier member in the recipient.

DETAILED DESCRIPTION

Aspects of the present invention are generally directed to securing an implantable medical device in a recipient (also referred to as a patient). The implantable medical device may be positioned adjacent to a reference structure in the recipient. An expandable portion of the stimulating medical device may be configured to expand during or after implantation to abut the reference structure to help secure the stimulating medical device relative to the reference structure.

Embodiments are described herein primarily in connection with one type of implantable medical device, a hearing prosthesis, and more specifically a cochlea implants. Cochlear implants generally refer to hearing prostheses that deliver electrical stimulation to the cochlear of a recipient. As used herein, cochlear implants may deliver electrical stimulation in combination with other types of stimulation, such as acoustic and/or mechanical stimulation. It would be appreciated that embodiments of the present invention may be implemented in any cochlear implant or other hearing prosthesis now know or later developed, including auditory brain stimulators (also known as auditory brainstem implants (ABIs)), or implantable hearing prostheses that acoustically or mechanically stimulate components of the recipient's middle or inner ear. Furthermore, it should be understood by those of ordinary skill in the art that embodiments may be implemented in implantable medical devices other than cochlear implants such as neurostimulators, cardiac pacemakers/defibrillators, etc. as well as other medical devices which temporarily or permanently implant, deliver or otherwise introduce into a recipient a therapeutic agent, sensor, electrode(s) or other active or passive component now or later developed.

Exemplary embodiments of a cochlear implant utilized in accordance with embodiments include a Contour™, Freedom™, Nucleus™ or Cochlear™ implant sold by Cochlear Limited, Australia. Such devices are described in U.S. Pat. Nos. 4,532,930, 6,537,200, 6,565,503, 6,575,894, and 6,697,674, which are hereby incorporated by reference herein. Similarly, cochlear implants utilizing a short array of electrode contacts are described in commonly owned and co-pending U.S. patent applications Ser. Nos. 11/605,952 and 11/605,951, which are hereby incorporated by reference herein.

FIG. 1is perspective view of a cochlear implant, referred to as cochlear implant100implanted in a recipient having an outer ear101, a middle ear105and an inner ear107. Components of outer ear101, middle ear105and inner ear107are described below, followed by a description of cochlear implant100.

In a fully functional ear, outer ear101comprises an auricle110and an ear canal102. An acoustic pressure or sound waves103is collected by auricle110and channeled into and through ear canal102. Disposed across the distal end of ear cannel102is a tympanic membrane104which vibrates in response to sound waves103. This vibration is coupled to oval window or fenestra ovalis112through three bones of middle ear105, collectively referred to as the ossicles106and comprising the malleus108, the incus109and the stapes111. Bones108,109and111of middle ear105serve to filter and amplify sound waves103, causing oval window112to articulate, or vibrate in response to vibration of tympanic membrane104. This vibration sets up waves of fluid motion of the perilymph within cochlea140. Such fluid motion, in turn, activates tiny hair cells (not shown) inside of cochlea140. Activation of the hair cells causes appropriate nerve impulses to be generated and transferred through the spiral ganglion cells (not shown) and auditory nerve114to the brain (also not shown) where they are perceived as sound.

Cochlear implant100comprises an external component142which is directly or indirectly attached to the body of the recipient, and an internal component144which is temporarily or permanently implanted in the recipient. External component142typically comprises one or more sound input elements, such as microphone124for detecting sound, a sound processing unit126, a power source (not shown), and an external transmitter unit128. External transmitter unit128comprises an external coil130and, preferably, a magnet (not shown) secured directly or indirectly to external coil130. Sound processing unit126processes the output of microphone124that is positioned, in the depicted embodiment, by auricle110of the recipient. Sound processing unit126generates encoded signals, sometimes referred to herein as encoded data signals, which are provided to external transmitter unit128via a cable (not shown).

Internal component144comprises an internal receiver unit132, a stimulator unit120, and a stimulating lead assembly118. Internal receiver unit132comprises an internal coil136, and preferably, a magnet (also not shown) fixed relative to internal coil136. Internal receiver unit132and stimulator unit120are hermetically sealed within a biocompatible housing, sometimes collectively referred to as a stimulator/receiver unit. Internal coil136receives power and stimulation data from external coil130, as noted above.

Stimulating lead assembly118has a proximal end connected to stimulator unit120, and a distal end implanted in cochlea140. Stimulating lead assembly118extends from stimulator unit120to cochlea140through temporal bone119. In some embodiments stimulating lead assembly118may be implanted at least in basal region116, and sometimes further into cochlea140. For example, stimulating lead assembly118may extend towards apex134of cochlear140. In certain circumstances, stimulating lead assembly118may be inserted into cochlea140via a cochleostomy122. In other circumstances, a cochleostomy may be formed through round window121, oval window112, the promontory123or through an apical turn147of cochlea140. As used herein the term “stimulating lead assembly,” refers to any device capable of providing stimulation to a recipient, such as, for example, electrical or optical stimulation. A such, it should be understood that stimulating lead assembly118merely provides one embodiment of an exemplary stimulating lead assembly, and other types of stimulating lead assemblies may be used in other embodiments.

Stimulating lead assembly118comprises a longitudinally aligned and distally extending array146of electrode contacts148, sometimes referred to as array of electrode contacts146herein, disposed along a length thereof. In most practical applications, array of electrode contacts146is integrated into stimulating lead assembly118. As such, array of electrode contacts146is referred to herein as being disposed in stimulating lead assembly118.

Stimulator unit120generates stimulation signals which are applied by electrode contacts148to cochlea140, thereby stimulating auditory nerve114. Stimulating lead assembly118preferably is positioned in cochlea140upon or immediately following implantation into cochlea140. It is also desirable that stimulating lead assembly118be configured such that the insertion process causes minimal trauma to the sensitive structures of cochlea140. Typically, stimulating lead assembly118is pre-curved, held in a substantially straight configuration at least during the initial stages of the implantation procedure, and then permitted to conform to the natural shape of the cochlea during and subsequent to implantation.

In cochlear implant100, external coil130transmits electrical signals (i.e., power and stimulation data) to internal coil136via a radio frequency (RF) link. Internal coil136is typically a wire antenna coil comprised of multiple turns of electrically insulated single-strand or multi-strand platinum or gold wire. The electrical insulation of internal coil136is provided by a flexible silicone molding (not shown). In use, implantable receiver unit132may be positioned in a recess of the temporal bone adjacent auricle110of the recipient.

The below discussed embodiments help minimize the risk of damage to the delicate structure of the cochlea on and following implantation of stimulating lead assembly118by helping secure stimulating lead assembly118upon insertion of stimulating lead assembly118into cochlea140.

FIGS. 2A-Care side views of an embodiment of electrode assembly118comprising an expandable portion240, prior to expansion. As will be discussed below, expandable portion240may help secure stimulating lead assembly118after implantation in the recipient.FIG. 2Aillustrates stimulating lead assembly118prior to insertion into cochlea140.FIG. 2Billustrates a view of stimulating lead assembly118following insertion, but prior to expansion of expandable portion240.FIG. 2Cillustrates a magnified view of the expandable portion240after insertion, but prior to expansion.

As illustrated, stimulating lead assembly118comprises a carrier member202that includes an expandable portion240, a distal end210, and a proximal end208. Distal end210terminates in tip211, and is adapted to be implanted furthest into cochlea140. A plurality of spaced-apart stimulation elements148, such as electrode contacts, are mounted or disposed on or in carrier member202between expandable portion240and tip211. It should be appreciated that as used herein, particular combinations of the terms mounted/disposed, in/on, etc., are not to be interpreted to refer to any particular manufacturing technique or structural relationship. Extending from proximal end208of carrier member202is a lead214. As used herein, the term stimulation element refers to any component, item, part, or device capable of providing stimulation, such as electrical or optical stimulation. Carrier member202may be manufactured from a silicone material, such as Silastic MDX 4-4210. Lead214physically and electrically connects stimulating lead assembly118with stimulator unit120(FIG. 1).

Stimulating lead assembly118may have a diameter of 0.8 mm (excluding expandable portion240) in the region intended to be positioned adjacent to the boney wall of cochlear240. Prior to expansion, expandable portion240may have a diameter slightly larger than that of stimulating lead assembly118immediately surrounding expandable portion240(e.g., a diameter of 0.9 mm). Or, for example, expandable portion240may also have a diameter equal to or less than that of the neighboring portions of stimulating lead assembly118(i.e., 0.8 mm). It should be noted that these diameters are exemplary only and in other embodiments, other sizes may be used. For example, in another embodiment, stimulating lead assembly118including expandable portion240, prior to expansion, may have a constant diameter of 0.6 mm. Further, although stimulating lead assembly118is illustrated as having a cylindrical cross-sectional shape that tapes towards tip211, it should be understood that stimulating lead assembly118may have other shapes, such as rectangular or square cross-sectional shape, a non-tapering shape, etc.

As shown inFIG. 2B, stimulating lead assembly118may be implanted into cochlea140through an opening204in temporal bone119and through an aperture in cochlea140. The aperture may be, for example, oval window112, round window121or a cochleostomy122, as described above with reference toFIG. 1. In this description, reference will be made to cochleostomy122(FIG. 1); it should be appreciated, however, that other embodiments may be configured to be implanted in oval window112, round window121, or other natural or man-made aperture in cochlea140.

As shown, expandable portion240may be only a small portion of stimulating lead assembly118. For example, the longitudinal length of expandable portion240may be only slightly larger than the width of the boney wall through which cochleostomy122passes. In one such embodiment, expandable portion240may have a length approximately 2 mm wider than the width of the boney wall of cochlea140, which typically has a width on the order of 1 mm. Then, expandable portion240may be positioned such that no more than 1 mm of expandable portion240(after expansion) extends into cochlea140and approximately 1 mm is located outside cochlea140. In one embodiment, expandable portion240may be marked by, for example, a physical or colored marker to aid the surgeon in placing expandable portion240inside cochleostomy122.

Restricting expandable portion240to the area close to cochleostomy122may help prevent the risk of expandable portion240expanding too far into cochlea140and potentially causing trauma to the delicate cochlear structures such as the osseous and spiral laminar. As will be discussed in further detail below, expandable portion240may have different shapes and lengths in different embodiments, and in certain embodiments may have a length greater or less than the width of the cochlea wall.

When implanted, the surface of carrier member202that faces the interior of cochlea140is referred to herein as the medial surface216of carrier member202. The opposing side of carrier member202, referred to herein as lateral surface218, faces the external wall and bony capsule (not shown) of cochlea140. It should be understood that the terms medial surface, medial direction, and the like, are generally used herein to refer to the surfaces, features and directions toward the center of cochlea140, while the terms lateral surface, lateral direction, and the like, are generally used herein to refer to surfaces, features and directions toward the exterior of cochlea140.

As would be appreciated by those of ordinary skill in the art, electrode contacts148may be disposed in a linear or non-linear array on or in carrier member202, and are typically positioned on or in carrier member202so as to align with predetermined regions of tonotopically mapped cochlea140when implanted in cochlea140. In alternative embodiments, electrode contacts148are implemented as described in U.S. patent application Ser. Nos. 11/605,951 (filed Nov. 30, 2006), 12/065,209 (filed Oct. 14, 2008), or 11/650,960 (filed Nov. 30, 2006), each of which are hereby incorporated by reference herein.

In an embodiment, electrode contacts148are half-band electrodes disposed in or on medial surface216of carrier member202. It should be appreciated, however, that any electrodes now or later developed suitable for a particular application may be used in alternative embodiments. For example, in one alternative embodiment, electrode contacts148are banded electrodes extending substantially around the circumference of carrier member202. In another embodiment, electrodes212do not laterally extend to or around the edges of carrier member202. Typically, each electrode contact148is arranged such that its exposed surface is substantially parallel to a longitudinal axis224of carrier member202. It should be appreciated, however, that other locations and orientations may be implemented in alterative embodiments. It should further be appreciated that the quantity of electrode contacts148may vary from as few as one or two to as many as twenty-four or more.

In certain embodiments, at least one electrode contact148has a surface that is at least adjacent medial surface216of carrier member202. In other embodiments, however, the surfaces of electrode contacts148may be raised above or recessed into medial surface216of carrier member202. It should be appreciated, however, that any embodiment of electrode contacts148may be implemented. Electrode contacts148may be manufactured from a biocompatible conductive material such as platinum, although other materials or combinations of materials may be used. In certain alternative embodiments electrode contacts148are coated with a biocompatible covering that does not interfere with the transfer of stimulation signals to cochlea140.

A variety of surgical methods may be used to implant a stimulating lead assembly118in a recipient, including a mastoidectomy and facial recess approach, a transcanal approach, or a combination thereof, depending upon the particular recipient anatomy, recipient needs and surgeon's discretion. For ease of description, embodiments of the present invention will be described with reference to implantation using a facial recess approach.

FIGS. 3A-3Billustrate stimulating lead assembly118after expansion of expandable portion240, in accordance with an embodiment.FIG. 3Aillustrates a view of stimulating lead assembly118extending through mastoid bone119and cochleostomy122; and,FIG. 3Billustrates a magnified view of expandable portion240after expansion. As illustrated, expandable portion240may expand so that it contacts the bone of cochlea140surrounding cochleostomy122. This may serve to effectively seal and stabilize (i.e., secure) stimulating lead assembly118in cochlea140.

Inserting unexpanded expandable portion240into cochleostomy122so that it is adjacent to the boney wall of cochlea140and allowing it to expand to abut the boney wall of cochlea140may help secure stimulating lead assembly118in cochlea140. Securing stimulating lead assembly118helps reduce the risk that stimulating lead assembly118may withdraw from or otherwise migrate in or from cochlea140, which could potentially result in damage to the sensitive cochlea structures and/or reduced effectiveness of the applied stimulation. Further, the electrode lead or other electrical conductors used in cochlear implants are typically robust to help cope with the body environment, these electrode leads have the potential to impart a slight force on the cochlear implant when implanted that could result in undesirable movement of the cochlear implant relative to the cochlea. Use of an expandable portion, such as the above discussed expandable portion240, may help counteract this force and maintain the cochlear implant in its desired position relative to the cochlea.

Sealing stimulating lead assembly118in cochlea140may help prevent cochlear fluid, such as perilymph, from leaking out of cochlea. Additionally, because expandable portion240may expand over a short duration of time, expandable portion240may more quickly seal cochlea140than prior techniques for sealing a cochea, such as using fibrous tissue, which may take a significant amount to integrate with the surrounding tissue.

In an embodiment, in which expandable portion240has a diameter of 0.8 mm prior to expansion, expandable portion240may have a diameter of approximately 1 to 1.2 mm after expansion. Or, for example, in an embodiment in which the expandable portion has a diameter of 0.6 mm prior to expansion, expandable portion240may have a diameter of approximately 0.8 to 1.0 mm after expansion. It should be noted that these diameters are exemplary only and that other diameters may be used.

In certain embodiments, expandable portion240comprises, for example, a portion of carrier member202with a layer of expandable material applied to the exterior surface of carrier member202. The properties of this material may be such that the material expands (e.g., swells) upon exposure to bodily fluid and/or saline solution. The layer of expandable material deposited on the surface of carrier member202may be thin relative to the dimensions of stimulating lead assembly118. The layer may be applied, for example with an applicator or sprayed onto carrier member202. Or, for example, an appropriate portion of carrier member202may be dipped in the expandable material. In an alternative embodiment, carrier member202may have a recess formed therein to receive the layer of expandable material. While depicted inFIG. 2with a diameter slightly greater than carrier member202, the recess, if utilized, may have a depth such that the diameter of expandable portion240is no greater or even less than the diameter of stimulating lead assembly118adjacent expandable portion240.

However, in other embodiments, rather than expandable portion240being a portion of carrier member202with a layer of expandable material, expandable portion240may be a separate member that is connected (either removably or non-removably) to carrier member202. That is, stimulating lead assembly118may be formed using three pieces (a proximal carrier member piece, an expandable member, and a distal carrier member piece) with a proximal carrier member piece located proximal to the expandable member (i.e., expandable portion240), a distal carrier member piece located distal to the expandable member, and the expandable member connecting the proximal and distal carrier member pieces. In such an example, the expandable member may comprise a lumen passing through the member through which the electrode leads (not shown) or other electrode conductors may pass. Further, in certain such embodiments, expandable portion240may have a cross-sectional shape that is similar to or matches the cross-sectional shapes of the distal and proximal carrier member pieces.

Or, in yet another embodiment, expandable portion240may be a collar that may be moved longitudinally along stimulating lead assembly118. This collar may be positioned on carrier member202during manufacture, or, for example, by a surgeon during implantation of stimulating lead assembly118. For example, expandable portion may be a separate collar or ring that may be slid over carrier member202by a surgeon prior to surgery. Then during surgery, the surgeon may position the collar or ring in cochleostomy122.

As noted above, expandable portion240may comprise a material that expands on exposure to moisture, such as bodily fluids, sterile saline or other solutions. The material may be a biocompatible hygroscopic material such as soft hygroscopic polymeric or hydrogel material. As an example, the biocompatible material can be a natural polymer such as a glycosaminoglycan, for example, hyaluronic acid, chondroitin sulfate, and cellulose or a synthetic polymer, such as a hydrogel, poly(vinyl alcohol), poly(2-hydroxyethylmethylacrylate), and polyethylene oxide. Other possible materials include collagen, chitosan, alginate, a poly(acrylonitrile)-based hydrogel, poly(ethylene glycol)/poly(acrylic acid) (PEG/PAA) interpenetrating polymer network (IPN) hydrogel, polyethylene oxide-polybutylene terephthalate (PEO-PBT), a hyaluronic acid based hydrogel, high-molecular-weight polyacrylic acid (PAA) as a filler in a Silastic™ matrix, PVA/chitosan blends, poly(hydroxy ethylmethacrylate), poly(ethylene glycol) (PEG) hydrogels, tetraethylene glycol diacrylate, polyethylene glycol methacrylate (PEGMA), cross-linkable (2-hydroxyethyl methacrylate) (HEMA), and poly(methyl acrylate-co-hydroxyethyl acrylate) hydrogel. Use of a soft polymeric material, which may stretch and thin, may be beneficial should stimulating lead assembly118need to be extracted out of cochleostomy122.

Or, for example, expandable portion240may comprise a shape memory material, such as Nitinol™, that swells or changes shape on exposure to body temperature. Or, in yet another embodiment, expandable portion240may comprise a material that expands on exposure to applied heat, a suitable source of electromagnetic radiation (e.g., UV light), an electric field, or other catalyst.

The degree to which expandable portion240expands may be chosen so that the when expanded, expandable portion240does not create excessive force or pressure on the surrounding boney wall of cochlea140, which may result in bone resorption/necrosis or result in disruption to intracochlear structures located just inside cochleostomy122. Further, the material selected for expandable portion240may be selected to have particular properties to control, for example, the onset and rate of expansion. For example, the material may be selected to have a particular rate of uptake of moisture and speed of expansion on exposure to a particular fluid, such as, body fluids and/or saline solution. The defined rate of moisture uptake may serve to define the rate of expansion of expandable portion240. In yet another embodiment, a beneficial compound may be impregnated within or otherwise releasable from the expandable portion240on expansion. For example, an antibacterial drug can be impregnated in the material comprising the expandable portion240that may be released (e.g., by dissolving in the presence of a fluid) upon expansion of expandable portion240. By helping secure the stimulating lead assembly118using a material that expands to its expanded dimensions in a relatively short amount of time, the surgeon may be able to complete the surgical implantation process in a shorter period of time, which may minimize the amount of time the cochlea is open during surgery and thus decrease the risk of damage to the cochlea's sensitive structures. This may be further beneficial in recipients that still have some residual hearing (e.g., particular frequencies).

In embodiments in which expandable portion240comprises a material that expands on exposure to fluids, the surgeon may keep the material dry prior to insertion, then after insertion and positioning of expandable portion240inside cochleostomy122, the surgeon may permit expandable portion240to come into contact with body fluids and/or apply a solution (e.g., saline solution) to cause expandable portion240to begin expanding.

In another embodiment, expandable portion240may comprise multiple materials. For example, in an embodiment, expandable portion240may comprise an outer layer and an inner layer. The inner layer may comprise an expandable material, such as noted above, and the outer layer may comprise a material that serves to prevent or delay exposure of the inner layer to moisture. In one such embodiment, the outer layer may be a polymeric material that may dissolve on exposure to fluid or solution at a rate that provides sufficient time for the surgeon to position stimulating lead assembly118within the recipient. Such an outer layer may serve to prevent exposure of the expandable inner layer to fluid or solution following stimulating lead assembly118placement for a period of, for example, between 30 seconds and 5 minutes, preferably between 1 and 2 minutes. Then, on being exposed to the fluid or solution, the expandable inner layer may expand to its second dimension in a time of, for example, between 10 and 40 seconds, more preferably about 20 seconds.

In another embodiment, the outer layer may comprise a relatively moisture impervious membrane, such as a biocompatible elastomeric material (e.g., a suitable polyurethane) that seals the expandable inner layer and prevents moisture ingress until the membrane is breached. In such an embodiment, the surgeon or another person may breach the membrane with a suitable tool or, for example, the membrane could be provided with frangible seals that can be cut or ripped once the carrier membrane is in the desired position. In another such embodiment, the membrane may have one or more ports through which an appropriate solution, such as sterile saline solution, can be injected when desired. The injection of such a solution may cause expandable portion240to expand thus breaching the membrane. Use of such a relatively moisture impervious membrane may provide the surgeon with the ability to control the timing of the onset of expansion thus enabling the surgeon to properly position stimulating lead assembly118prior to initiating the expansion of expandable portion240.

Referring again toFIG. 1, in an implantation procedure utilizing the facial recess approach, stimulating lead assembly118is inserted during an operation that usually takes between 2-3 hours, depending on the device to be implanted. An incision is made behind outer ear101to expose temporal bone119. Temporal bone119consists of several segments (not shown) known as the squamous, the mastoid, the tympanic, the zygomatic and the petrous segment. Typically, traditional cochlear implants require the opening of the mastoid segment of temporal bone119which leads to middle ear105.

Following the opening of the incision behind outer ear101, a shallow recess is created in the mastoid to hold internal receiver unit132and stimulator unit120. Next, additional amounts of the mastoid are removed. By removing this additional portion of the mastoid, the surgeon opens an area known as the facial recess. The facial recess is a concave portion of the inner side of the mastoid bone that opens to middle ear105, and inner ear107. As the facial recess is opened, the surgeon is able to access middle ear105and inner ear107.

The surgeon then prepares cochleostomy122in cochlea140to allow implantation of stimulating lead assembly118into cochlea140. As noted above, the opening may be formed through round window112, oval window121, the promontory or through the apical turn of cochlea140. Stimulating lead assembly118is then gently threaded into the shell-like structure of cochlea140. Depending in the type of implant used, the opening may either remain open to heal with scar tissue, or may be closed by the surgeon. The procedure is completed by closing the incision behind outer ear101.

Cochleostomy122may be drilled so that it provides an opening into cochlea140that is slightly larger than the diameter of stimulating lead assembly118. Thus, only a slight amount of expansion by expandable portion240may effectively seal and secure stimulating lead assembly118in cochlea140without producing an excessively high and undesirable amount of pressure on the bone surrounding cochleostomy122.

FIG. 4illustrates a perspective view of the right side of a recipient showing the location of implantation of certain embodiments of the stimulating lead assembly in accordance with the facial recess approach. It should be appreciated, however, that embodiments of the present invention are equally applicable to other implantation methods. Directional arrows430,432,434and436illustrate general directions in relation to the recipient. Directional arrow430illustrates the inferior direction, and refers to a direction that is towards the feet of the recipient. Directional arrow432illustrates the posterior direction, and refers to a direction that is towards the back of the recipient's head. Directional arrow434illustrates the superior direction, and refers to a direction that is towards the top of the recipient's head. Directional arrow436illustrates the anterior direction, and refers to a direction that is towards the front of the recipient's head.

As illustrated inFIG. 4, facial recess462is positioned between the facial nerve410and the cord-tympani nerve412. Facial recess462may be opening204(FIG. 2). Facial nerve410is positioned posterior to facial recess462, and cord-tympani nerve412is positioned anterior to facial recess462. Visible behind facial recess462is round window121of cochlea140. In some embodiments of the present invention, stimulating lead assembly118is configured to be implanted through facial recess462and into round window121.

FIGS. 5A and 5Bare side views of an embodiment of stimulating lead assembly comprising a stop member, in accordance with an embodiment. InFIGS. 5A-Bstimulating lead assembly118is referred to as stimulating lead assembly500. InFIG. 5A, the stimulating lead assembly is illustrated prior to insertion in a recipient's cochlea;FIG. 5B, following insertion. Stimulating lead assembly500comprises a carrier member202having a proximal end208and a distal end210. Distal end210terminates in tip211, and is adapted to be implanted furthest into cochlea140. A plurality of spaced-apart electrode contacts148are disposed in carrier member202along medial surface216of carrier member202between expandable portion540and tip211. The opposing side of carrier member202is referred to herein as lateral surface218. Lead214extends from proximal end208.

Attached to or integral with carrier member202are a stop member504and an expandable portion540. Expandable portion540is positioned between stop member504and all, and, in embodiments in which not all electrodes212are to be inserted into cochlea115, some of electrode contacts148. Stop member504is positioned on carrier member202between proximal end208and expandable portion540, and as illustrated, stop member404may be adjacent to expandable portion540. Expandable portion540may comprise an expandable material, such as discussed above. Stop member504may be manufactured from a non-expandable material, such as silicone, and in embodiments may be a contiguous portion of carrier member202. Further, stop member504may have a diameter greater than that of the adjacent portion of carrier member202and expandable portion540, prior to expansion. Or, in other embodiments, stop member540may be manufactured from an expandable material, such as discussed above, that may be expanded during or after implantation of stimulating lead assembly118similar to the above-discussed expandable portion240.

Stimulating lead assembly500may be surgically inserted using a similar mechanism as discussed above with reference toFIGS. 2-4. In this example, however, stop member550may be located along carrier member202in a position such that stimulating lead assembly500is properly positioned in cochlea140when stop member540abuts the boney wall of cochlea140surrounding cochleostomy122. Thus, during implantation of stimulating lead assembly500, the surgeon may insert carrier member202into cochlea140until stop member504contacts the exterior surface of cochlea140surrounding cochleostomy122, thus indicating that stimulating lead assembly118is properly positioned. The surgeon may then allow expandable portion540to expand in order to seal and/or secure stimulating lead assembly500. Stop member504may be, for example, a stop member such as described in U.S. patent application Ser. No. 12/052,193 filed Mar. 20, 2008, which is hereby incorporated by reference.

FIG. 6is a side view of one embodiment of stimulating lead assembly118, referred to herein as stimulating lead assembly600, comprising a fixation structure, in accordance with an embodiment. Fixation structure650may help reduce the ability of stimulating lead assembly600to exit or rotate within cochlea140following implantation. InFIG. 6, stimulating lead assembly600is shown in an implanted position, and is viewed from an anterior direction of the recipient. Stimulating lead assembly600comprises a carrier member202, having proximal end208and distal end210, terminating in tip211. A plurality of spaced-apart electrode contacts148are disposed in carrier member202along medial surface216of carrier member202. The opposing side of carrier member202is referred to herein as lateral surface218. Lead214extends from proximal end208.

Attached to or integral with carrier member202are expandable portion540and stop member504as described above with reference toFIGS. 5A and 5B. Fixation structure650is positioned at or near proximal end208of carrier member202to substantially interact with at least a portion of the bone surrounding facial recess204. In the specific embodiment shown inFIG. 6, fixation structure650comprises a series of circumferentially-extending projections670. If circumferentially-extending projections670are viewed along a plane that extends longitudinally through fixation structure650, each projection may have, for example, a substantially triangular cross-sectional shape.

Fixation structure650may comprise a material that expands in the presence of fluids (e.g., body fluids and/or saline solution), such as the above-discussed expandable materials (e.g., hygroscopic materials, multiple layers, etc.). In such an embodiment, a surgeon may insert stimulating lead assembly118into cochlea140with fixation structure650and expandable portion540in their unexpanded states. The surgeon may insert stimulating lead assembly118until stop504contacts the bone surrounding cochleostomy122, such as was discussed above with reference toFIG. 5. Then, the surgeon may allow fixation structure650, stop member504, and/or expandable portion540to expand. Any of the above, techniques discussed with reference toFIG. 2may be used in permitting fixation structure650and expandable portion540to expand, such as, for example, using an expandable portion comprising inner and outer layers, etc.

InFIG. 6, circumferentially-extending projections670are dimensioned to extend from carrier member202to bone119surrounding facial recess204. The above-noted tendency of stimulating lead assembly600to exit cochlea140places pressure on fixation structure650to exit the recipient. However, the pressure from carrier member202causes circumferentially-extending projections670to further interact with bone119. This interaction produces a longitudinal anchor force that substantially prevents longitudinal movement (that is, movement in a direction approximately parallel to the longitudinal axis of the device) of fixation structure650out of the recipient. This resulting longitudinal anchor force is a force along the longitudinal axis of stimulating lead assembly600in the direction of cochlea140. The longitudinal anchor force maintains fixation structure650in bone119thereby retaining carrier member202in a desired position in cochlea140. In other words, the longitudinal anchor force prevents substantial longitudinal movement of carrier member202out of cochlea140.

As noted, embodiments of stimulating lead assembly600may include half-band electrodes. For optimal stimulation, a stimulating lead assembly utilizing half-band electrodes is preferably maintained in a desired position and orientation within cochlea140. However, due to certain aspects of the implantation procedure, a rotational force may be created on stimulating lead assembly600that causes stimulating lead assembly600to twist within cochlea140. If stimulating lead assembly600twists within cochlea140, the half band electrodes will no longer be in a desired orientation for optimal stimulation. In such embodiments, fixation structure650may be configured to produce an additional anchor force that prevents rotation of stimulating lead assembly600within cochlea140. This additional anchor force is referred to herein as a rotational anchor force. As stimulating lead assembly600attempts to twist within cochlea140, the torque causes circumferentially-extending projections670to further interact with bone119. This additional interaction produces a rotational anchor force that substantially prevents rotational movement of fixation structure650. As a result of this rotational anchor force rotational movement substantial of carrier member202is also prevented.

In other embodiments, fixation structure605may be manufactured from a material that does not expand in the presence of fluids. For example, in one such embodiment, fixation structure650comprises a flexible material having a diameter that is larger than facial recess204. In such embodiments, during implantation, flexible fixation structure650is forced in to facial recess204and is compressed therein. As fixation structure650attempts to exit cochlea140, the compression of fixation structure650by bone119creates the longitudinal anchor force that prevents movement of fixation structure650out of cochlea140. In such embodiments, fixation structure650may comprise a flexible component such as silicone, polyurethane, PTFE, etc.

In other embodiments, the longitudinal anchor force created by the interaction of fixation structure650and bone119may be the result of friction. As stimulating lead assembly600attempts to exit cochlea140, the friction between fixation structure650and bone119produces the longitudinal anchor force that prevents movement of stimulating lead assembly600. In certain embodiments, fixation structure650may have a rough or uneven surface that increases friction with bone119.

As would be understood to those of ordinary skill in the art, the bone surrounding facial recess204is typically not a smooth surface, and likely has burrs and marks resulting from its interaction with surgical tools, as well due to the structural features of bone119. For example, bone119naturally includes aerated sections that form openings in the bone. Such attributes of bone119tend to increase the friction between fixation structure650and bone119. In further embodiments, the surface of bone119may be purposefully scored to further increase the friction with fixation structure650.

In yet an alternative embodiment, fixation structure650may comprise a malleable material such as a metal or a hard plastic or a shape-memory material that changes shape upon heating to body temperature or other catalyst such has IR or UV light, to anchor itself into the recess in bone119. In such embodiments fixation structure650may comprise materials such as titanium, platinum, stainless steel, chromium, nitinol, etc. In one particular embodiment, the shape-memory material comprises a shape-memory polymer. A further description of exemplary fixation structures is provided in the above-incorporated U.S. patent application Ser. No. 12/052,193 filed Mar. 20, 2008.

FIG. 7is a side view of an embodiment of stimulating lead assembly118, referred to herein as stimulating lead assembly700, configured to reduce the ability of stimulating lead assembly700to exit cochlea140following implantation. InFIG. 7, stimulating lead assembly700is shown in an implanted position, and is viewed from an anterior direction of the recipient. Stimulating lead assembly700comprises a carrier member202, having proximal end208and distal end210terminating in tip211. A plurality of spaced-apart electrode contacts148are disposed in carrier member202along medial surface216of carrier member202. The opposing side of carrier member202is referred to herein as lateral surface218. Lead214extends from proximal end208. As in the embodiment ofFIG. 7, embodiments of stimulating lead assembly700may include half-band electrodes.

Attached to or integral with carrier member202are expandable portion540and stop member504as described above with reference toFIGS. 5A and 5B, and fixation structure750. Fixation structure750is positioned at or near proximal end208of carrier member202to substantially interact with at least a portion of the bone surrounding facial recess762.

In the specific embodiment illustrated inFIG. 7, facial recess762may be shaped by the surgeon such that facial recess762has an outer portion763that is narrower than an inner portion764of facial recess762. Fixation structure750may comprise a material that expands in the presence of fluids (e.g., body fluids and/or saline solution), such as the above-discussed expandable materials. In such an embodiment, a surgeon may insert stimulating lead assembly118into cochlea140with fixation structure750and expandable portion540in their unexpanded states. The surgeon may insert stimulating lead assembly118until stop504contacts the bone surrounding cochleostomy122, such as was discussed above with reference toFIG. 5. Then, the surgeon may allow fixation structure750and expandable portion540to expand from their unexpanded state (i.e., a first dimension) to their expanded state (i.e., a second dimension). Any of the above, techniques discussed with reference toFIG. 2may be used in permitting fixation structure750and expandable portion540to expand, such as, for example, using an expandable portion comprising inner and outer layers, an expandable portion that is a collar than can slide over carrier member202, etc. . . .

In the specific embodiment shown inFIG. 7, fixation structure750in its expanded state circumferentially extends from carrier member202such that fixation structure750abuts the interior surface of outer portion763and the diameter of fixation structure750is greater than that of the outer portion763of facial portion762. Fixation structure750has a diameter less than that of inner portion764and when inserted fits within inner portion764. In this example, fixation structure750expands after insertion such that the fixation structure abuts and pushes on the inner surface of outer portion763to exert a longitudinal force that pushes stimulating lead assembly118toward cochleostomy122thus creating a compression and help prevent longitudinal movement of stimulating lead assembly118(that is, movement in a direction approximately parallel to longitudinal axis of stimulating lead assembly118).

In other embodiments, fixation structure705may be manufactured from a material that does not expand in the presence of fluids. For example, in one such embodiment, fixation structure750comprises a flexible material having a diameter that is larger than the outer portion763of facial recess762. In such embodiments, during implantation, flexible fixation structure750is forced through outer portion763and into inner portion764. As fixation structure750attempts to exit cochlea140, the compression of fixation structure750by the inner surface of bone119surrounding outer portion763creates the longitudinal anchor force that prevents movement of fixation structure750out of cochlea140. In such embodiments, fixation structure750may comprise a flexible component such as silicone, polyurethane, PTFE, etc.

In yet other embodiments fixation structure750may comprise a flexible component or a malleable material such as a metal or a hard plastic or a shape-memory material that changes shape upon heating to body temperature or other catalyst such has IR or UV light, to anchor itself into the recess in bone119, such as discussed above with reference toFIG. 6.

Although the embodiments ofFIGS. 2, and4-7illustrate an expandable portion that is cylindrical in shape, in other embodiments the expandable portion may have alternative configurations. The below discussedFIGS. 8-12provide exemplary alternative configurations for the expandable portion. Each of these alternative configurations may be used in any of the above-discussed embodiments of FIGS.2and4-7.

FIG. 8is a side view of an exemplary configuration for the expandable portion that has a variable thickness, in accordance with an embodiment. As illustrated, expandable portion800, in its expanded state, has a thickness that varies longitudinally along the length of carrier member202. Expandable portion800may formed using techniques such as discussed above with reference toFIG. 2. In the illustrated example ofFIG. 8, expandable portion800is formed by applying a layer of expandable material802to carrier member202. This layer of expandable material802may surround carrier member202and have a thickness that is thicker in its longitudinal middle than at its edges. Although, illustrated, as a layer of expandable material applied to carrier member202, in other embodiments, expandable portion800may be formed using other techniques, such as, for example, expandable portion800may be a separate member connecting an distal and proximal section of carrier member202, a collar or ring, may comprise separate layers, etc.

FIG. 9is a side view of an exemplary configuration for the expandable portion that has a variable thickness, in accordance with an embodiment. Expandable portion900may be used, for example, as expandable portion240(FIG. 2).

As illustrated, expandable portion900, in its expanded state, comprises three humps902A,902B, and902C that extend radially from carrier member202. In the illustrated example ofFIG. 9, expandable portion900is formed by applying a layer of expandable material with a variable thickness to carrier member202. Although illustrated as a layer of expandable material applied to carrier member202, in other embodiments, expandable portion900may be formed using other techniques, such as, for example, those discussed above with reference toFIG. 2(e.g., expandable portion900may be a separate member connecting an inner and outer section of carrier member202, a collar or ring, may comprise separate layers, etc).

Use of an expandable portion with a variable thickness such as discussed above with reference toFIGS. 8-9may be beneficial in helping avoid sharply swelling structures from migrating into the cochlea and potentially damaging the delicate structures inside the cochlea. They also may offer an improved seal and fixation in recipient's with an unevenly cut cochleostomy.

FIG. 10Aillustrates a cross-sectional view of an exemplary configuration for expandable portion that may expand from only a portion(s) of the circumference of a carrier member, in accordance with an embodiment. Expandable portion1000may be used, for example, as expandable portion240(FIG. 2).

As illustrated in its expanded state, expandable portion1000comprises two opposing layers of expandable material1002A and1002B that extend radially from opposite sides the circumference of carrier member202. Thus, prior to expansion, the cross-section of expandable portion1000may have a circular shaped, and then after expansion, the cross-section of expandable portion1000may have an oval shape. In an embodiment, expandable portion1000may be used with a cochleostomy122cut with a slot shape.FIG. 10Billustrates a cross-section of a slot shaped cochleostomy1022, in accordance with an embodiment. During implantation of stimulating lead assembly118, expandable portion1000may be positioned in cochleostomy1022so that when expanded, expandable portion1000will match the shape of cochleostomy1022(i.e., so that expandable portion1000expands along the long axis of the oval shaped cohcleostomy).

Use of an expandable portion and shaped cochleostomy, such as expandable portion1000and cochleostomy1022, may help provide rotational orientation and stability of stimulating lead assembly118. For example, as noted above, in an embodiment, electrode contacts148may be located on medial surface216of carrier member202, which preferably should face the interior surface of cochlear140(FIG. 3A). Use of an expandable portion and shaped cochleostomy, such as expandable portion1000and cochleostomy1022, may help maintain such a rotational orientation.

It should noted that expandable portion1000and shaped cochleostomy1022are but one example of an expandable portion with expandable material only a portion of the circumference of carrier member202and a matching shaped cochleostomy. For example, in other embodiments, the shaped cochleostomy may have other shapes, such as, an oval shape that is longer in the vertical axis, a rectangular shape, etc. Or, for example, expandable portion1022may have only single portion along its circumference with a layer of expandable material, multiple portions, etc.

In other embodiments, expandable portion240(FIG. 2) may be formed by applying a number of straight strips, spiral strips, spots, rings, or other patterns of expandable material along or around carrier member202. Using such patterns may or may not form a full seal, but may help stabilize the location and orientation of stimulating lead assembly118in cochlea140.

FIG. 11illustrates a cross-section and side view of an exemplary configuration for the expandable portion that comprises strips of expandable material, in accordance with an embodiment. As illustrated, expandable portion1100comprises a plurality strip of expandable material1102A,1102B,1102C, and1102D applied longitudinally along carrier member202. Expandable portion1100may be used, for example, as expandable portion240(FIG. 2). Although illustrated as a layer of expandable material applied to carrier member202, in other embodiments, expandable portion1100may be formed using other techniques, such as, for example, those discussed above with reference toFIG. 2(e.g., expandable portion1100may be a separate member connecting an inner and outer section of carrier member202, a collar or ring, may comprise separate layers, etc).

FIG. 12illustrates a side view of an exemplary configuration for the expandable portion that comprises a plurality of rings, in accordance with an embodiment. Expandable portion1200may be used, for example, as expandable portion240(FIG. 2). As illustrated, expandable portion1200comprises three rings1202A,1202B, and1202C that extend radially from and circumferentially around carrier member202. Each of these rings1202A-C may be formed by, for example, sliding a ring of expandable material over carrier member202, by applying a layer of expandable material to carrier member202, or by, for example, any of the other techniques discussed above (e.g., multiple layers of material, etc.). Further, the portions of expandable portion1200not covered by rings1202A-C may or may not comprise expandable material. If entire expandable portion1200comprises expandable material, when exposed to fluid, the entire expandable portion may expand, as illustrated. Or, alternatively, only rings1202A-C may comprise expandable material.

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.