Is the cochleovestibular nerve function affected in patients with hemifacial spasm?

Hemifacial spasm (HFS) is a motor disorder caused by the vascular compression of the facial nerve in the posterior fossa. The cochleovestibular nerve is close to the facial nerve and shares the same entry to the periphery, also has disorders caused by vascular compression. We evaluated the cochleovestibular nerve function in patients with HFS based on the hypothesis that vascular compression, which causes HFS, can also affect the nearby cochleovestibular nerve function. The medical charts of 49 patients with surgically confirmed HFS were reviewed retrospectively. The results of the pure-tone threshold, auditory brainstem response (ABR), video head impulse test (vHIT), and magnetic resonance imaging were analyzed. In each patient, the HFS side and the unaffected side were compared in the paired manner. The anterior inferior cerebellar artery was the major offending vessel (69.4%). There were no significant differences in the pure-tone threshold, properties of ABR waves, and vHIT gain. There was no evidence of cochleovestibular nerve compression syndrome in all patients. The angulation of the nerve by the offending vessel was more frequently identified in the HFS side than in the unaffected side (p = 0.040). The effect of HFS on cochleovestibular nerve function is limited.