Acoustic neuromas. Progression of hearing impairment and function of the eighth cranial nerve

The results obtained by conventional otologic evaluation are reported for fifty-nine patients with acoustic neuromas, sixty-one patients primarily suspected of an acoustic neuroma but in whom Pantopaque cisternography had invalidated the diagnosis, and in seventy-one patients with Meniere's disease. The audiologic tests were confined to the following: pure-tone audiometry, speech audiometry, recruitment examination by ABLB and Metz recruitment tests, and examination for reflex decay a.m. Anderson. Nineteen patients had an audiogram taken at their initial visit with the otologist, and already at this examination--4.2 years before the diagnosis was made--a high-tone hearing impairment was present. Fourteen patients had anacusis in the tumor ear and one patient had an impairment of 90 dB. The audiologic evaluations are based only on patients with hearing equal to or better than 80 dB. There was no connection between preoperative hearing impairment and the age at operation, and anacusis was found in all age groups. Four patients had recruitment by the ABLB test and six patients by the Metz recruitment test. When these two tests were combined, two patients had recruitment by both tests. Twenty percent had pathologic stapedial reflex decay. Only one patient had a normal differential caloric test. It is concluded that the typical patient with an acoustic neuroma has a gradually increasing unilateral hearing impairment of eight years' duration. A pronounced high-tone impairment with PTA of 55 dB and a poor discrimination score are to be expected. The patient is uncertain at pure-tone threshold determination and displays a lack of recruitment at both ABLB and Metz recruitment tests. The patient has a decreased or nonexistent differential caloric reaction in the ear in question. A normal differential caloric test does in all probability exclude an acoustic neuroma; however, all possible audiometric and anamnestic configurations may be encountered, and deviation from the "typical" picture should not lure the investigator into excluding the presence of a neuroma.