Blepharospasm should be differentiated from hemifacial spasm (HFS). HFS is characterized by intermittent synchronous gross contractures of the entire side of the face and is rarely bilateral (Video 12-8). HFS often begins in the periocular region and then progresses to involve the entire half of the face. Unlike BEB, HFS persists during sleep.
HFS is often associated with ipsilateral facial nerve weakness. In most cases, HFS is the result of a vascular compression of the facial nerve root exit zone at the brain stem. Magnetic resonance imaging (MRI) often reveals the ectatic vessel. MRI can also help rule out other cerebellopontine angle lesions that may be the cause in less than 1% of cases. Neurosurgical decompression of the facial nerve may be curative in HFS, but it exposes the patient to the relative risk of neurosurgical intervention. Periodic injection of botulinum toxin is a commonly used, effective treatment option for HFS (see Fig 12-25). Oral medications, including drugs with membrane-stabilizing properties such as carbamazepine and clonazepam, are used less frequently because of their low efficacy.
Hemifacial spasm. Courtesy of Pete Setabutr, MD.
Aberrant regeneration after facial nerve palsy may also present with hemifacial contracture and synkinetic facial movements. The history (eg, previous Bell palsy, trauma) and clinical examination are distinctive. Functionally troublesome synkinetic facial movements often respond well to botulinum toxin injection.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.