SIMULTANEOUS COMPARISON BETWEEN TRANSTYMPANIC AND EXTRATYMPANIC ELECTROCOCHLEOGRAPHY

Electrocochleography (ECoG) has become a mainstay in the diagnostic ar mamentarium used by otolaryngologists and audiologists in the evaluati on of patients suffering auditory and vestibular symptoms. Controversy exists, however, regarding the relative accuracy of ECoG when recorde d with a non-invasive external auditory canal (EAC) electrode as compa red to that recorded using a transtympanic electrode. In an effort to resolve this controversy, 19 healthy volunteers (37 ears) with no hist ory of otologic disease or symptoms and a normal screening pure-tone a udiogram were studied. For each volunteer, a transtympanic electrode w as placed on the cochlear promontory bilaterally under iontophoretic a nesthesia followed by the immediate placement of an EAC TIPtrode (Etym otic Research Laboratory, Elk Grove Village, Illinois). Signals from b oth the transtympanic electrode and the TIPtrode were recorded simulta neously following click stimulus using the Nicolet CA 1000. Preliminar y analysis of these recordings identify no significant difference in s ummating potential/action potential ratios between EAC and transtympan ic electrodes in this normal subject population.