Hearing Outcome Following Microvascular Decompression for Hemifacial Spasm: Series of 1434 Cases

Although hearing impairment after microvasuclar decompression (MVD) for hemifacial spasm (HFS) is not common, its occurrence could detrimentally affect the patient's surgical outcome. The object of this study is to address the optimal approaches for reducing postoperative hearing problems after MVD for HFS. We retrospectively analyzed the medical records of patients with HFS who underwent MVD with the same surgeon at our institute from March 2003 to October 2016, and reviewed the pertinent literature. Patients who were followed up for more than 6 months were selected, resulting in the analysis of 1434 total patients. Postoperative hearing complications were evaluated audiometrically and subjectively (patient-reported symptoms). Clinical factors such as the intraoperative findings were reviewed to identify their correlation with auditory function. Symptoms in 1333/1434 patients (93.0%) resolved more than 90% from their preoperative state. Among them, 16 patients (1.1%) complained of hearing impairment after surgery. Most impairment was transient, although 6/1333 patients (0.4%) required additional interventions for persistent hearing deficits (one surgical intervention and five hearing aids). A >50% decrease in the amplitude of brainstem auditory evoked potentials during the operation was significantly associated with postoperative hearing deficits. Few auditory complications, mostly transient, result from MVD. Although MVD is a commonplace surgical technique, to reduce complications it is important to emphasize the need for clean exposure of the lower cranial nerves (except for cranial nerve VIII) to obtain enough working space, sharp arachnoid dissection, minimal cerebellar retraction, and proper responses to changes identified during intraoperative monitoring.