Acoustic neuromas with normal pure tone hearing levels

Area of Science:

• Neurology
• Otolaryngology
• Audiology

Background:

• Acoustic neuroma (vestibular schwannoma) is a benign tumor arising from the Schwann cells of the vestibulocochlear nerve.
• While hearing loss is a hallmark symptom, some patients present with normal pure-tone hearing thresholds.

Observation:

• This study reviewed 408 primary acoustic neuroma resections between 1966 and 1983.
• Twenty-one patients (5%) exhibited preoperative pure-tone hearing levels within normal limits (≤25 dB HL at 500, 1000, 2000 Hz).
• Common symptoms included dysequilibrium (67%) and subjective hearing impairment (62%), with nystagmus as a frequent physical finding.

Findings:

• Five patients (23%) demonstrated completely symmetric hearing across all tested frequencies.
• The average speech discrimination score was 90%, and mean tumor size was 2.4 cm.
• Brainstem evoked response audiometry (BSER) proved most valuable in evaluating these patients with normal hearing.

Implications:

• Acoustic neuromas should be considered even in patients with normal pure-tone audiometry.
• A comprehensive clinical evaluation, including detailed history, physical examination, and targeted audiological testing, is crucial for diagnosing acoustic neuromas in this subgroup.
• Early diagnosis can lead to timely intervention and potentially better management of neurological and auditory symptoms.