Hemifacial spasm is a neuromuscular disorder characterized by frequent involuntary contractions (spasms) of the muscles on one side (hemi-) of the face (facial). The disorder occurs in both men and women, although it more frequently affects middle-aged or elderly women. It is much more common in the Asian population. 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. The condition may be caused by a facial nerve injury, or a tumor, or it may have no apparent cause. Rarely, doctors see individuals with spasm on both sides of the face. Most often hemifacial spasm is caused by a blood vessel pressing on the facial nerve at the place where it exits the brainstem.
Surgical treatment in the form of microvascular decompression, which relieves pressure on the facial nerve, will relieve hemifacial spasm in many cases. Botulinium toxin (Abotox®) injections are ineffective in producing control of the spasm and result in varying degrees of facial weakness. These injections, which need to be repeated, may also have a negative impact on subsequent definitive surgical treatment.
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