Auditory findings after stereotactic radiosurgery in acoustic neurinoma.

Auditory function after gamma knife stereotactic radiosurgery (GK) was evaluated in 22 patients with newly diagnosed unilateral acoustic neurinoma who had had some measurable hearing preoperatively. No tumor growth was observed in any patients. The preservation rates for useful hearing (n = 13) and any measurable hearing (n = 22) were 62% and 86%, respectively, at 2 years after GK. Postoperative hearing dysfunction was attributed to progressive cochlear impairment in 13 patients and to progressive injury in the retrocochlear auditory pathway in 5 patients. Hearing tended to be well preserved when caloric response was unchanged postoperatively. Preservation of hearing was not associated with the initial tumor volume, decrease of tumor size, maximum tumor dose, or peripheral tumor dose.