COMPARATIVE PSYCHOPHYSICAL EVALUATION IN COCHLEAR IMPLANTATION - ELECTRICAL AND MAGNETIC STIMULATION

Transtympanic electrical stimulation, either in the form of round wind ow or promontory placement of electrode prior to cochlear implantation is an accepted and commonly used psychophysical tool. Certain respons e parameters have been identified as predictors of outcome. This study compared the subjective auditory responses generated by promontory el ectrical stimulation (PES) with those from two noninvasive modalities, namely peritympanic electrical stimulation (PTES) and transcranial ma gnetic stimulation (TMS). Ten postlingually deafened adult cochlear im plant candidates were studied. Standard psychophysical parameters were obtained from patients undergoing PES and PTES. A more subjective for m of evaluation was conducted for TMS. Subsequently, nine patients rec eived the multichannel Nucleus (Cochlear Corp., Denver, CO, U.S.A.) im plant and one patient a Clarion (Advanced Bionics, Sylmar, CA, U.S.A.) implant. Compared with PES, PTES elicited increased threshold respons es with similar dynamic ranges between 50 and 400 Hz of stimulation. T he differences were, by and large, insignificant. PTES appeared to be a useful alternative in selected individuals owing to its noninvasiven ess. TMS, on the other hand, was incapable of clearly inducing auditor y percepts. It also produced concomitant facial and trigeminal stimula tion, limiting its potential use as a prognostic tool.