[Caloric test in low-tone sensorineural hearing loss]

Acute low-tone sensorineural hearing loss (ALHL) is generally has a relatively good prognosis. We have often found in long-term following-up, however, that ALHL relapses, recurs or develops into Meniere's disease. Diagnostic criteria of the Acute Altitude Deafness Research Group of the Ministry of Health, Labor, and Welfare of Japan, define ALHL as low-tone-disorder sensorineural hearing loss without vertigo in which cochlear symptoms -ear fullness, tinnitus, and deafness- develop suddenly. Over the last five years, we have treated 31 cases of ALHL, in about half of which neurotological examination showed potential peripheral vestibular dysfunction on testing positional nystagmus (a) with closed eyes and (b) in a dark room with open eyes, and by finding laterality in the peripheral labyrinth system on caloric test. These cases show high canal paresis -a maximum slow- phase eye velocity of caloric nystagmus exceeding 60%. These results, taken together, suggest that derangement extends to the peripheral labyrinth system in patients with ALHL.