Evaluation of patients for cochlear implant by promontory stimulation: Psychophysical responses and electrically evoked brainstem potentials

The protocol for assessing patients for cochlear implantation at University College Hospital and the Royal National Institute for the Deaf, London, includes a session of electrophysiological tests and electrical stimulation of the cochlea. Electrocochleography is performed with the object of excluding non-organic hearing loss and of clarifying the site of deafness. Using the same transtympanic needle, AC and DC electrical stimulation is performed to establish whether patients perceive a sensation of sound, dynamic range and ability to detect frequency shifts. Tinnitus suppression was produced by AC and DC stimulation. It is likely that AC suppression of tinnitus occurs by a masking effect. Electrically evoked auditory brainstem potentials were recorded in one patient.