[Incidence of normal hearing in acoustic neuroma]

Unilateral or asymetrical sensorineural hearing loss, tinnitus and instability classically represent the main symptoms for the suspected diagnosis of acoustic neurinoma. In literature there are very few studies which refer about acoustic neurinoma in patients with normal hearing. In this article we report the results of a retrospective analysis of 155 acoustic neurinoma cases with normal hearing managed in our center in the last 7 years. These patients are classified in two groups: 1) with normal hearing at the time of diagnosis and 2) with at least a mild sensorineural hearing loss. Of this 155 cases, 21 (13.5%) had normal pure tone audiogram. An important characteristic of these patients, in comparison with the group with normal hearing, is the younger age. Tinnitus, instability, sudden hearing loss with complete recovery and vertigo are the most common symptoms. The mean pure tone threshold is 14.7 dB, speech audiometry is positive in very few cases, while a large number of cases show false negative. ABR are positive in 90.5% of cases, and demonstrate its high sensitivity for retrococlear pathology. The mean tumor size shows significant differences between the group with normal hearing and this with hearing loss. We believe that the presence of this symptoms in a young patient should necessitate complete neurotologic examination and in the patients with normal hearing a high level of suspicion represents the first step for early diagnosis of small tumors; the next step is the through evaluation of patient with pure tone audiogram, ABR, and imaging studies, preferably MRI with gadolinium, as this permits the diagnosis of small intracanalicular tumor. Thus, in cases of small tumors with good hearing we feel that will be possible to adopt hearing conservation surgical approach like FCM and retrosigmoid approach in more cases.