Cochlear electrode with drug delivery channel and method of making same

An implantable flexible cochlear electrode array comprising:

• an elongate flexible carrier insertable into the scala tympani of a human cochlea;
• a multiplicity of electrode contacts exposed on a surface of the flexible carrier, wherein each electrode contact comprises a flat platinum electrode exposed only on a front surface of the flexible carrier, the front surface comprising that surface of the flexible carrier that is placed closest to a modiolar wall of the scala tympani when the electrode array is inserted into the scala tympani;
• a multiplicity of wires embedded within the flexible carrier, each wire having a distal end connected to a respective electrode contact and a proximal end connectable to a tissue stimulation device;
• and
• a drug delivery channel passing longitudinally through the flexible carrier.

A method of making an implantable electrode array having a drug delivery channel passing therethrough, the method comprising:

• (a) attaching electrode contacts made from a precious, biocompatible material to a foil sheet made from a non-toxic but chemically-active metal;
• (b) connecting a wiring system to the metal contacts;
• (c) positioning a flexible tube over the wiring system, the flexible tube having a lumen passing therethrough;
• (d) molding a flexible polymer carrier around the electrode contacts, wiring system and flexible tube while such are held in place by the foil sheet;
• and
• (e) etching away the foil sheet, leaving the electrode contacts exposed at a surface of the molded polymer carrier;
• whereby a flexible implantable electrode array is made, and wherein the lumen of the flexible tube comprises a channel through which drugs or other liquids may be delivered to a distal tip of the electrode array.

A method of inserting a short cochlear electrode array through the round window membrane into the scala tympani of a human cochlea, the cochlear electrode array comprising an elongate flexible carrier having a retention collar having an engaging diameter “D” thereon, at least one electrode contact exposed on a surface of the carrier and located distally from the retention collar, at least one wire embedded within the flexible carrier having a distal end connected to the at least one electrode contact and a proximal end connectable to a tissue stimulation device, the method comprising the steps of:

• (a) forming a hole having a diameter “D” in the round window membrane;
• (b) attaching a proximal end of the short cochlear electrode array to an insertion tool;
• (c) inserting a distal end of the short cochlear electrode array through the opening in the round window membrane until the retention collar engages the round window membrane;
• and
• (d) removing the insertion tool from the proximal end of the short cochlear electrode array.

An implantable flexible cochlear electrode array comprising:

• an elongate flexible carrier insertable into the scala tympani of a human cochlea;
• at least one electrode contact exposed on a surface of the flexible carrier;
• at least one wire embedded within the flexible carrier, said at least one wire having a distal end connected to the at least one electrode contact and a proximal end connectable to a tissue stimulation device;
• a drug delivery channel passing longitudinally through the flexible carrier;
• and
• a retention collar formed proximally on the flexible carrier so that the at least one electrode contact lies distally therefrom, the retention collar having a shoulder adapted to engage an opening created in the round window membrane at the entrance of the scala tympani, whereby the retention shoulder anchors the electrode array within the scala tympani.