A hemifacial spasm is where the muscles on one side of the face twitch involuntarily. Also referred to as 'tic convulsif', hemifacial spasm is caused by damage to - or pressure on - the facial nerve (the 'seventh cranial nerve' or 'CNVII'), which controls facial muscles and transmits taste from the tongue and mouth to the brain.
Hemifacial spasm may indicate an underlying condition. Similar to trigeminal neuralgia, pressure on the facial nerve may be as a result of a blood vessel (the anterior inferior cerebellar artery) or a tumour pressing on the nerve.
Facial twitches may start as almost imperceptible movement of the eyelid, mouth or cheek, however over time they can begin to affect other parts of the face. Hemifacial spasm is more common in women than in men, tends to affect people after the age of 40. Hemifacial spasm can be very disabling, and patients often notice fatigue in the facial muscles, avoiding social interactions because of the embarrassment associated with these involuntary movements.
Tests / Diagnosis
The diagnosis of hemifacial spasm involves a review of symptoms and medical history, and the diagnosis is based mainly on history and examination. If episodes are infrequent, patients may record footage of their hemifacial spasm for documentation. Tests are often used to exclude other diagnoses, and may include an initial CT (computed tomography) and/or MRI (magnetic resonance imaging) scan of the brain. Blood tests may also be recommended to review any risk factors as outlined above. Sometimes, facial EMG and vestibular tests may be performed to confirm the diagnosis.
First-line treatment for hemifacial spasm usually involves Botox injections into the affected facial muscles. These are usually performed by neurologists with special interests in Botox. When the effects of Botox wear off and if episodes between Botox treatments shorten, microvascular decompression can be performed. This involves an operation behind the ear and separating a blood vessel, usually the anterior inferior cerebellar artery from pressing on the facial nerve.