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Hemifacial Spasm

Hemifacial spasm, or tic convulsif, is a neuromuscular disorder characterized by frequent involuntary contractions of the muscles on one side of the face. These tics are usually not painful (although there is a sensory component to the facial nerve that can produce pain behind the ear, hearing changes are also noted by some patients) and initially affect only one side of the face. The disorder occurs in both men and women, although it more frequently affects middle-aged or elderly women.

Causes

The condition may be caused by a facial nerve injury or a tumor, or it may have no apparent cause. Most commonly, hemifacial spasm is caused by irritation of the seventh cranial nerve (the facial nerve). A small vessel (usually an artery but occassionally a vein) is often found to be compressing the root entry zone of the facial nerve at the brainstem.

Symptoms

The first symptom is usually an intermittent twitching of the eyelid muscle that can lead to forced closure of the eye. The spasm may then gradually spread to involve the muscles of the lower face, which may cause the mouth to be pulled to one side. Eventually the spasms involve all of the muscles on one side of the face almost continuously.

Diagnosis

In the majority of cases, imaging of the brain does not reveal a cause of the nerve irritation. In such cases, a small vessel (usually an artery but occassionally a vein) is often found to be compressing the root entry zone of the seventh cranial nerve at the brainstem. This vessel is usually too small to be demonstrated by imaging studies such as magnetic resonance imaging (MRI), computed tomography (CAT scan), or even angiography (arteriography).

Treatment

Treatment of hemifacial spasm frequently consists of injecting botulinum toxin (commonly called Botox) into the affected muscles to produce a temporary partial paralysis. This procedure needs to be repeated approximately every six months.

Patients with the most severe symptoms often choose microvascular decompression, an effective microsurgery procedure to reposition the artery that irritates the nerve as it comes out of the brainstem. Microvascular decompression consists of making an incision behind the ear and then a small opening (about one inch) in the skull. This allows the surgeon to see where the blood vessel is pressing on the nerve. Once the area of compression is seen, the blood vessel(s) is separated from the nerve and a small pad is placed on the nerve to prevent further contact. Recovery from this procedure is brief - most patients can be discharged from the hospital one or two days after surgery.

The majority of patients who have this procedure performed by a qualified neurosurgeon have no further facial tics and require no further medications.

While serious complications are rare, microvascular decompression has the highest risks of all hemifacial spasm treatments and should only be conducted in a major medical center with highly skilled neurosurgeons and neurologists. Despite the good outcome from surgery, it is an operation that has serious potential risks, and a decision to undergo the procedure should be made with an understanding of its risks as well as the benefits. The most frequent complication is loss of hearing on the same side, but this occurs in less than 10% of patients and is usually slight.

Post-operative relief of the spasm is usually immediate, but in some cases it sputters for a matter of weeks before stopping permanently. Rarely, a delayed facial weakness occurs, but invariably it is temporary and transient. Late recurrence of the spasm is extremely rare. The occasional early recurrence reflects some technical error or an incorrect diagnosis.

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