VESTIBULAR FUNCTION IN BILATERAL PROGRESSIVE SENSORINEURAL HEARING-LOSS

To investigate the vestibular function in patients with bilateral prog ressive sensorineural hearing loss, we examined 5 cases using electron ystagmography. Cases 1, 2 and 3 were adult type, and Cases 4 and 5 juv enile type. All patients had dizzy spells in the early stage of the di sease, and showed spontaneous nystagmus. Bilateral reduction of calori c response and very low vestibule-ocular reflex (VOR) gain on rotation testing were observed in Cases 1, 2 and 3. Case 4 showed right canal paresis upon the caloric test and left directional preponderance upon the rotation test. Case 5 showed good responses to both tests. Optokin etic afternystagmus (OKAN) in Cases 2, 3 and 5 was not brisk, and Case s I and 2 showed directional preponderence of OKAN. OKAN was useful fo r detecting directional preponderance. We believe there are two types of this disease which correlate with vestibular function. One type is associated with high grade vestibular dysfunction while, in the other, vestibular function is reasonably good.