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Hemifacial Spasm (HFS)

Essential Facts for Patients

Symptoms

Hemifacial spasm (HFS) is a chronic neurological disorder manifested by involuntary twitching or spasms around one eye or one side (hemi-) of the face (facial). It involves the muscles that are innervated by the facial nerve (cranial nerve VII). The disease affects both women and men, being more common in middle-aged women. Though it occurs worldwide, it is more common in Asia.

In the initial stages, there is usually intermittent twitching of the muscles of eyelids which can result in forceful eye closure. Later these twitches involve muscles of the lower face. During each spasm, the angle of the mouth may be pulled outward and there can also be simultaneous spasms of the muscles beneath the jaw bone. In later stages, spasms may be very frequent and sometimes continuous. Often the movements are precipitated by contraction of the facial muscles during speaking, eating or while closing the eyes. Stress or tiredness can precipitate or worsen the movements. The spasms are painless, though there may be discomfort.

Cause

In most instances the cause of HFS remain unknown. HFS is often caused by a blood vessel pressing on the facial nerve at the place where it exits the brainstem. Less frequently, HFS may occur after injury to the facial nerve or by intermittent pressure over the facial nerve caused by a benign tumour.

Diagnosis

The diagnosis of HFS can be easily made by a neurologist based on the typical characteristics of the movement disorder and a detailed neurological examination. The doctor may ask for a brain imaging to look for any structural causes of HFS. However, in most cases brain imaging is normal. 

Treatment

HFS can be treated effectively with regular Botulinum NeuroToxin injections in the overactive (twitching) muscles of the face. Improvement lasts for an average of 3 months but may last longer. There can be side effects after injection, such as swelling, soreness of skin and local bleeding which usually resolve in a few days. Some patients can have drooping of the injected eyelid, watering or dryness of the eye, and sagging of the angle of the mouth on the side of injection. The latter may appear like a facial palsy with mild difficulty in speaking and deviation of the angle of the mouth on the unaffected side when speaking.  These are due to excessive dose of injection and usually disappear in a few weeks. Drug therapy is generally not effective. Carbamazepine, clonazepam and baclofen can reduce intensity and frequency of spasms, but can cause side effects such as drowsiness, nausea, and skin rash. Surgical treatment in the form of microvascular decompression is indicated to those who have an abnormal blood vessel pressing the facial nerve and causing HFS. However there can be significant side effects of the surgical procedure, including facial nerve damage.

Prognosis

The prognosis of HFS depends on the cause, severity, and treatment response. Residual spasms can occur after years of injection therapy and are usually tolerable. Some individuals gradually become free of spasms after injection therapy and just need treatment occasionally. However, some patients, especially those with severe symptoms, have depression and tend to withdraw socially. They will need appropriate therapy and counselling.