Delayed facial weakness after microvascular decompression of cranial nerve VII.

BACKGROUND: Retromastoid craniectomy and microvascular decompression of cranial nerve VII for hemifacial spasm is a well accepted and effective treatment. Risks of the operation relate to the surgical approach in general and to the seventh nerve in particular. Delayed facial weakness is an unusual and little-described complication of the procedure. The purpose of this review is to describe this complication and the characteristics of the patients so affected.
METHODS: Between 1972 and 1996, 985 patients have undergone microvascular decompression for hemifacial spasm. During this time, 28 patients (2.8%) undergoing decompression of the facial nerve and 1 patient undergoing decompression of the cochlear nerve for tinnitus developed delayed facial palsy.
RESULTS: The weakness was at least a House Grade III or worse and was complete in 11 of the patients. The time to occurrence averaged 12 days, with a tight range of 7 to 16 days. There were no factors such as duration of symptoms, intraoperative findings, or preoperative botulinum injections that were predictive of this postoperative weakness. In all patients there was almost complete recovery (House Grade I or II).
CONCLUSIONS: Delayed facial weakness after MVD of CN VII can occur in up to 3% of cases. The onset of weakness after operation is consistent in its timing, occurring on average 12 days after the procedure. Although the etiology of this complication is uncertain, the palsy spontaneously resolves with a good or excellent outcome.