Acoustic neuroma in patients with completely resolved sudden hearing loss

Approximately 30% of patients with sudden hearing loss show complete recovery. Researchers have long questioned whether extensive evaluation is necessary in these cases. Recently, however, with the increasing widespread application of magnetic resonance imaging, a higher rate than expected of acoustic neuromas has been detected in patients with sudden hearing loss. Two studies have suggested that affected patients may even partially regain hearing. The aim of the present clinical study was to determine whether acoustic neuroma-induced hearing loss may be associated with full recovery. The files of 67 patients evaluated for sudden hearing loss at Rabin Medical Center from 1989 to 2000 were reviewed. All patients underwent pure tone audiometry, acoustic reflex tests, and auditory brain stem evoked response tests. Hearing evaluation was followed by magnetic resonance imaging scan and, 1 month later, a second hearing test. Findings were compared between patients with and without evidence of tumor on imaging, and between patients with tumor with and without full recovery. Twenty-four patients (36%) had a diagnosis of acoustic tumor, of whom 4 (16.7%) recovered hearing after 1 month. All 4 tumors were intracanalicular. Two of these patients had low-tone hearing loss, and 2 had flat curves; 3 had a pathological auditory brain stem evoked response. Of the 43 patients without tumors, 26 (60%) showed complete resolution of the hearing loss. We conclude that complete recovery of hearing loss does not exclude acoustic tumor, and these patients therefore require full evaluation. The reason for the recovery remains unclear.