PROMONTORY TESTING IN NEUROTOLOGIC DIAGNOSIS

The ability of promontory testing (PT) to differentiate a retrocochlea r from a cochlear lesion in a group of 88 patients having unilateral s ensorineural hearing loss was assessed. Promontory stimulation was per formed, using the Nucleus Promontory Stimulator (model Z10012, Cochlea r Corporation, Melbourne, Australia), by placing a needle electrode tr anstympanically on the basal turn of the cochlea. Patients with measur able hearing gave inconsistent results. Patients who had undergone eig hth nerve section or translabyrinthine removal of acoustic neuroma wer e used as controls. They had no perception of sound in response to ele ctrical stimulation, and were unable to perform any part of the PT, Of nine patients with anacusis secondary to an acoustic neuroma, six wer e unable to perceive sound in response to electrical stimulation or pe rform any aspect of the PT. Of the three patients able to perceive sou nd, only one could perform the temporal difference limen (TDL) and gap detection (CAP) test. In patients with total deafness from other caus es, 80 percent (24\30) were able to perceive sound with electrical sti mulation, 46 percent (14\30) performed TDL, and 70 percent (21\30) per formed the GAP tests. In patients with unilateral total deafness, prom ontory testing may aid in differentiating retrocochlear from cochlear lesions and help identify patients at risk for acoustic neuroma.