Implantable neuro-stimulation electrode with fluid reservoir

Abstract

An implantable electrode with a fluid reservoir is described. An implantable electrode carrier has an outer surface including electrode contacts for electrically stimulating nearby neural tissue. A fluid reservoir within the electrode carrier stores a volume of therapeutic fluid. At least one fluid delivery port connects the fluid reservoir to the outer surface of the electrode carrier for delivering the therapeutic fluid from the fluid reservoir to the outer surface. A delivery septum port is in fluid communication with the fluid reservoir for delivering the therapeutic fluid to the fluid reservoir.

Description

[0001] The present application is a continuation-in-part of U.S. application Ser. No. 11 / 374,505, file Mar. 13, 2006, which is a divisional application of U.S. application Ser. No. 10 / 281,066, filed Oct. 24, 2002, and issued as U.S. Pat. No. 7,044,942, which in turn claimed priority from U.S. Provisional Application Ser. No. 60 / 336,452, filed Oct. 24, 2001; U.S. Provisional Application Ser. No. 60 / 394,427, filed Jul. 8, 2002; U.S. Provisional Application Ser. No. 60 / 394,602, filed Jul. 9, 2002; and U.S. Provisional Application Ser. No. 60 / 417,704, filed Oct. 10, 2002. The present application also claims priority from U.S. Provisional Application Ser. No. 60 / 780,667, filed Mar. 9, 2006; all of which are incorporated herein by reference.FIELD OF THE INVENTION [0002] The invention relates to a drug eluting cochlear implant electrode for the transient elution of a pharmacological agent into the inner ear. BACKGROUND ART [0003] Electrical stimulation of the inner ear has been very succes...

AI Technical Summary

Benefits of technology

[0014] The at least one fluid delivery port is at least one slit or channel in the material of the electrode carrier, or a semi-porous membrane that connects the fluid reservoir to the outer surface

Problems solved by technology

But the insertion of the electrode causes a variable amount of connective tissue growth and trauma.

The amount of trauma is very difficult to predict and depends on the cochlea anatomy, the electrode design, and the insertion technique.

Tissue growth and trauma may limit the performance of the implant.

And trauma to spiral ganglion cells is cumulative and cannot be undone in the present state of technology.

Unfortunately, most cochlear implant electrodes on the market today require significant force to be inserted, even for distances which are much less than the full length of the scala tympani.

Damage and trauma cause bleeding, inflammation, perforation of soft tissue, tears and holes in membranes, and fracture of thin osseous structures.

The resulting damage may cause loss of surviving hair cells, retrograde degeneration of the dendrite which inervates the organ of Corti, and in the worst case, spiral ganglion cell death in the Rosenthal's canal.

Cell death means that quantitatively less neural tissue is available for stimulation, and qualitatively that fewer frequency-tuned fibers are available to represent frequency information.

Further loss of hair cells and loss of dendrites without loss of spiral ganglion cells means that acoustic stimulation is no longer possible, and that no synergetic effects between acoustic and electric stimulation is available.

Another inconvenience with cochlear implants is the rise in measured electrode impedance post-surgery.

This rise is thought to be caused by encapsulation of the electrode by a tight membrane which reduces the efficiency of electric stimulation by creating a zone with ionic depletion around the contacts.

But as the electrode is introduced in the fluid of the scala tympani, the medical solution quickly dissolves and may not reach a location where it would be most beneficial.

One problem with round window drug delivery is that the membrane permeability to molecular substances changes over the course of a day, and that large molecules cannot pass through the tight membrane.

There is no easy existing way to deliver medicine into the inner ear after cochlear implantation.

The middle ear is not easily accessed and the inner ear is a sealed system that does not allow direct deposition or injection of medicines except at the time of cochlear implant surgery.

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