Vestibular function in bilateral progressive sensorineural hearing loss.

To investigate the vestibular function in patients with bilateral progressive sensorineural hearing loss, we examined 5 cases using electronystagmography. Cases 1, 2 and 3 were adult type, and Cases 4 and 5 juvenile type. All patients had dizzy spells in the early stage of the disease, and showed spontaneous nystagmus. Bilateral reduction of caloric response and very low vestibulo-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. Optokinetic afternystagmus (OKAN) in Cases 2, 3 and 5 was not brisk, and Cases 1 and 2 showed directional preponderance of OKAN. OKAN was useful for 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.