Cerebellopontine angle tumors causing hemifacial spasm: types, incidence, and mechanism in nine reported cases and literature review.

OBJECTIVE: Although hemifacial spasm is usually caused by vascular compression around the root exit zone of the facial nerve, it is sometimes brought on by a cerebellopontine angle tumor. We reviewed and analyzed data from past experience with hemifacial spasm induced by cerebellopontine angle tumors.
METHODS: Nine patients of a total 2,050, who had presented with hemifacial spasms associated with cerebellopontine angle tumors between 1986 and 2009, were reviewed.
RESULTS: Two vestibular schwannomas, five meningiomas, and two epidermoid tumors were included in this study. Hemifacial spasm occurred on the same side of the lesion in eight patients whereas it occurred on the opposite side of the lesion in one patient. With respect to the pathogenesis of hemifacial spasms, offending vessels were found in six patients, tumor encasement of the facial nerve in one patient, hypervascular tumor compression of the facial nerve without offending vessels in one patient, and a huge tumor compressing the brain stem and, thus, contralateral facial nerve compression in one patient. Hemifacial spasm was resolved in seven patients, whereas in two patients with a vestibular schwannoma and an epidermoid tumor, it improved transiently and then recurred in a month.
CONCLUSIONS: Each type of tumor had different characteristics with respect to the induction of hemifacial spasm; therefore, it is suggested that neurosurgeons, who are planning surgeries both for the purposes of relieving hemifacial spasm and removal of cerebellopontine angle tumor, should thoroughly prepare appropriate approaches and specific dissecting strategies according to each causative lesion.