ACUTE HEARING-LOSS FOLLOWING FRACTIONATED STEREOTACTIC RADIOSURGERY FOR ACOUSTIC NEUROMA - REPORT OF 2 CASES

Two cases of acute hearing loss are reported following fractionated st ereotactic radiosurgery for acoustic neuroma. Both patients had neurof ibromatosis type 2 and were treated with a peripheral tumor dose of 21 Gy delivered in three fractions (7 Gy each) with a minimum interfract ion interval of 10 hours. One patient who had previously undergone sur gical resection of the treated tumor presented with only rudimentary h earing in the treated ear secondary to an abrupt decrease in hearing p rior to treatment. That patient reported total loss of hearing before complete delivery of the third fraction. The second patient had modera tely impaired hearing prior to treatment; however, within 10 hours aft er delivery of the final fraction, he lust all hearing. Both patients showed no improvement in response to glucocorticoid therapy. Possible explanations for this phenomenon are presented.