Audiological and Vestibular Functions in Patients With Lateral Semicircular Canal Dysplasia and Aplasia

The aim of the present study was to evaluate audiologic and vestibular functions in patients with lateral semicircular canal (LSCC) dysplasia/aplasia.

We conducted a retrospective study of a patients with LSCC dysplasia and aplasia at tertiary referral center. The subjects included 15 patients with LSCC dysplasia or aplasia, with or without combined inner ear anomalies. Medical history, temporal bone computed tomography scans, pure-tone audiograms, and vestibular function test results were analyzed.

LSCC anomaly was identified in 15 patients (20 ears). Nine patients had unilateral LSCC dysplasia only and showed a mean pure-tone average of 45.5±28.7 dB, while three patients (33.3%) among them had normal hearing. Six patients had bilateral LSCC dysplasia/aplasia combined with other inner ear anomalies and profound bilateral hearing loss. Notably, only four out of 15 patients (26.7%) had dizziness symptoms. On caloric test, patients with isolated LSCC dysplasia showed a 51.8%±29.3% level of canal paresis (eight out of nine patients showed anomalies), whereas patients with bilateral LSCC dysplasia/aplasia presented bilateral vestibular loss. One patient with isolated LSCC underwent video-head impulse test; horizontal canal gain decreased to 0.62 (17% asymmetry) and anterior canal gain was 0.45 (52.6% asymmetry), whereas posterior canal gain was normal.

Bilateral LSCC dysplasia/aplasia is comorbid with other inner ear anomalies and presents as profound bilateral hearing loss and vestibulopathy. In contrast, isolated unilateral LSCC dysplasia presents as ipsilateral horizontal canal paresis. Hearing function in isolated LSCC dysplasia is usually, but not always, impaired with varying severity.