AB-Intra- and Post-Operative Measures of Auditory Function

Background and Objectives of the Study

Cochlear Implantation A cochlear implant (CI) is a prosthetic device for the inner ear that bypasses damaged inner ear hair cells and directly stimulates the auditory nerve, thereby providing audible sensations to patients with sensorineural hearing loss (SNHL). The implanted part consists of a hermetically sealed electronics package, a receiver coil which communicates with external components, and a magnet to help align the internal and external receiver coils. Attached to the implant package is the lead assembly that includes an array of electrode contacts that is inserted into the cochlea and interacts with its stimulable elements, the spiral ganglion cells and the cochlear hair cells. Today's CI models have between 12 and 22 intra-cochlear electrode contacts, each of which can be independently stimulated. In the healthy cochlea, different pitches are perceived at distinct locations along the length of the cochlea. This tono-topic organization is utilized when stimulating the cochlea electrically, as individual contacts can preferentially address neural populations associated with discrete regions of the cochlea. For example, when a low-pitched sound is captured by the microphone of the external sound processor, stimulation is routed to more apical electrodes, while for high-pitched sounds more basal electrode contacts are engaged.

Performance and Candidacy

Cochlear implants are currently the standard-of-care for patients with significant SNHL and poor speech understanding. Preservation of the delicate anatomy within the cochlea is well-known to correlate with hearing and speech understanding outcomes. During electrode insertion, it is common for the surgeon to make subtle adjustments to insertion parameters such as the angle of insertion or speed of insertion; such modifications are part of the standard-of-care of conventional CI surgery. The current state of conventional CI electrode insertion provides the surgeon with no feedback as to whether and when the delicate structures of the cochlea are damaged. Such a tool by which the surgeon can obtain real-time measurements of the electrophysiological function of the cochlea could help improve the current surgical procedure.

Electrocochleography