Although several studies have previously reported on patients presenting with 'normal' audiologic parameters in acoustic neuroma, the present study is, to our knowledge, the first to exclusively examine in detail cases involving exceptionally stringent objective audiometric features. Of 369 patients with acoustic neuroma who were operated on between April 1980 and April 1997 by our group, 10 had strictly normal hearing, defined as follows: (1) puretone average < 20 dB; (2) speech discrimination score > 90%; and (3) interaural differences ≤ 10 dB at every hertz level. A high level of audiologic functioning was found to significantly lower the sensitivity of auditory brainstem response in the detection of acoustic neuroma. Magnetic resonance imaging was the only preoperative test exhibiting 100% sensitivity in this setting. Thus, a high level of clinical suspicion appears warranted in any case involving unexplained unilateral audiovestibular symptoms - including those instances in which strictly normal hearing parameters exist and are associated with negative auditory brainstem response findings.
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