[Acute hearing loss in the contralateral ear after acoustic tumor removal]

Two patients suffered from acute hearing loss of the contralateral side after acoustic tumor surgery were reported. The first patient was a 42-year-old-male. He had had a right progressive hearing loss over two years and CT scan revealed a mass of 20mm in diameter in the right cerebellopontine angle. The patient noticed the contralateral hearing loss on next morning after the total removal of tumor by translabyrinthine approach. However he had no complaint of vertigo or facial palsy. An audiogram of the contralateral side just after the onset showed flat type audiogram of sensorineural hearing loss with positive recruitment. With steroid therapy for two weeks, hearing and ABR findings improved and returned to nearly normal. The second case was a 47-year-old male. The patient had chronic renal failure treated by hemodialysis. His hearing loss in the right ear had gradually decreased over two years and an acoustic tumor of 2.5cm in diameter was demonstrated by CT scan. The tumor was removed by translabyrinthine approach. Nine day after the operation, he noted total deafness in contralateral ear and vertigo. He was given steroid hormone and his hearing improved up to 68 dB. Four cases have been reported in the literature. The mechanisms of acute sensorineural hearing loss observed in these cases were discussed. The cause remained unknown, however there were some hypothesis such as the compression to the opposite brainstem, peripheral nerve or feeding vessels by tumor or brain edema after operation, and local vasospasms might be also the cause of hearing impairment.(ABSTRACT TRUNCATED AT 250 WORDS)