Hearing threshold difference between ears and risk of acoustic tumor.

This study addresses the question, what difference in hearing between ears puts a patient at sufficient risk of acoustic tumor to warrant further diagnostic tests? The subjects were 210 patients with surgically confirmed unilateral acoustic tumors and a control group comprised of 112 patients referred for audiometry. Hearing thresholds were determined at octave intervals from 250 Hz to 8 kHz. The threshold in the nonsuspect ear was subtracted from the threshold in the suspect ear. The rank order in effectiveness for threshold difference was: 2 kHz, 4 kHz, 1 kHz, 8 kHz, 500 Hz, and 250 Hz. We found that the most effective diagnostic strategy was to refer patients for magnetic resonance imaging if their average threshold difference at 1 to 8 kHz was 20 dB or greater and refer patients for auditory brainstem response testing if their average threshold was 5 to 20 dB.