Hemifacial spasm

Hemifacial spasm (HFS) is a neuromuscular movement disorder characterized by involuntary, irregular, tonic or clonic contractions of the muscles innervated by the facial nerve (cranial nerve VII) on one side of the face. The condition typically begins with intermittent twitching of the orbicularis oculi muscle around the eye and may progressively spread to involve other ipsilateral facial muscles, including those of the cheek, mouth, and platysma in the neck. In rare cases, bilateral involvement can occur. The spasms may persist during sleep and can be exacerbated by stress, fatigue, or voluntary facial movements. The most common cause of hemifacial spasm is neurovascular compression of the facial nerve at its root exit zone from the brainstem, most frequently by an aberrant or ectopic blood vessel such as the anterior inferior cerebellar artery or posterior inferior cerebellar artery. Less common causes include tumors, demyelinating lesions, or other structural abnormalities in the posterior fossa. The condition predominantly affects adults, with onset typically occurring in the fourth to sixth decades of life, and has a slight female predominance. Treatment options include botulinum toxin injections, which are considered the first-line therapy and provide temporary relief by weakening the affected muscles. Injections typically need to be repeated every three to six months. Microvascular decompression (MVD) surgery is the only potentially curative treatment, involving the placement of a cushioning material between the offending blood vessel and the facial nerve. MVD has high success rates but carries surgical risks including hearing loss and facial weakness. Oral medications such as carbamazepine, baclofen, and clonazepam may provide modest symptomatic relief but are generally less effective than botulinum toxin or surgery.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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