Hemifacial Spasm
- Involuntary contraction of the facial muscles on one side
- Attributed to pathologic excitability of the facial nerve
- Common causes: idiopathic, compression of the facial nerve from an aberrant superior cerebellar artery or anterior inferior cerebellar artery
- Uncommon cause: cerebellopontine angle or brainstem mass
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Core clinical features
- Facial muscles on one side of the face contract intermittently in unison, drawing up that side of the face
- Contractions prominently involve the upper facial muscles, but lower facial muscles are usually also involved
- Social interactions often trigger or exacerbate these contractions
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Imaging features
- Heavily T2-weighted MRI may show compression of the root of the facial nerve by an aberrant vessel
- MRI or CT may show a mass in the cerebellopontine angle or pons
- Consider ordering brain MRI/MRA to rule out a pontine lesion or a compressive lesion of the facial nerve root
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Tip: if ipsilateral hearing loss or trigeminal hypesthesia is present, you must order brain imaging because an intracranial mass lesion is the likely cause
- If imaging is negative, prescribe botulinum toxin injections into the affected side of the face
- For botulinum-refractory cases, consider sub-occipital surgical decompression with placement of a separator between the facial nerve root and an aberrant intracranial artery, even if imaging fails to show corroborative abnormalities
- Botulinum toxin injections usually relieve symptoms for 3–4 months, can be repeated, and will usually provide long term relief
- In botulinum failures, sub-occipital surgical decompression is usually effective, but includes a risk of stroke and deafness