[Vestibular function in bilateral idiopathic progressive sensorineural hearing loss].

To investigate vestibular function in patients with bilateral progressive sensorineural hearing loss (BPSHL), we examined 5 cases using electronystagmography. Cases 1, 2 and 3 were adult type, cases 4 and 5 were 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 VOR (vestibulo-ocular reflex) gain on rotation testing were observed in cases 1, 2 and 3. Case 4 showed right canal paresis on the caloric test and left directional preponderance on 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 4 showed directional preponderance of OKAN. Although OKAN is useful for detecting directional preponderance, it does not always reflect peripheral vestibular function. We suggest the existence of two types of BPSHL which correlate with vestibular function. One type is associated with high grade vestibular dysfunction while, in the other, vestibular function is fair.