Acoustic Neuromas with Normal Pure Tone Hearing Levels

From 1966 through 1983, 408 patients underwent primary removal of an acoustic neuroma at the Mayo Clinic. Of these, 21 had preoperative pure tone hearing levels of 25 dB hearing loss or better at 500, 1000, and 2000 Hz, which for this study was defined as normal pure tone hearing. Fourteen patients (67%) had dysequilibrium and 13 (62%) had subjective hearing impairment. Nystagmus was the most common physical finding. Five patients (23%) had completely symmetric pure tone hearing levels through all frequencies tested. The mean speech discrimination score was 90%. Mean tumor size was 2.4 cm. Brain stem evoked response audiometry was the most helpful of the special tests in the evaluation of these patients with normal pure tone hearing levels. Our results suggest that 5% of patients with acoustic neuromas have normal pure tone hearing levels. A careful history, a thorough physical examination, and an appropriate selection of tests will identify these patients.