[Clinical study of time-shift evoked potentials]

Quick change of the interaural time difference (ITD) generates moving sound stimuli. Specific biphasic event-related potentials called "time-shift evoked potentials (TSEPs)" can be recorded when this moving sound is given. The results of TSEPs in various types of hearing loss were analyzed in comparison with auditory brainstem response (ABR) and slow vertical response (SVR) in order to evaluate clinial applicability of TSEPs. Firstly, the detection threshold of TSEPs was established in groups of patients with low tone sensorineural hearing loss and with steep high tone sensorineural hearing loss. The usefulness of TSEPs was then evaluated in patients with retrocochlear hearing loss and with functional deafness. The patients with retrocochlear hearing loss were divided into 2 subgroups, one with auditory nerve disorder and the other with cortical disorder. It was found that TSEPs participate in the transference of auditory time-factors. They reflect the function of not only the auditory nerve and brainstem which form major components of ABR, but also the central nervous system superior to the inferior colliculus. TSEPs could be recorded in most patients with functional deafness and are more useful for its diagnosis than using the conventional directional hearing test. It is concluded that TSEPs is useful as a clinical test for detection of cortical disorder and functional deafness.