Hemifacial spasm is characterized by unilateral twitching of the muscles of the face around the eye and or mouth. The twitching is usually intermittent and occurs many times a day. Women are affected slightly more than men. It causes significant social embarrassment. The etiology of this condition is unknown. The twitching is involuntary and usually involves the muscles supplied by facial nerve or  7^th cranial nerve. Most of the cases are idiopathic whereas some cases may result due to compression of the facial nerve by an aberrant blood vessel in the brainstem area. Most of the cases are sporadic. The twitching of the muscles becomes worse with stress, fatigue, anxiety and is relieved in sleep.

 DIAGNOSIS: Hemifacial spasm may be confused with blepharospasm. Hemifacial spasm is usually unilateral where as blepharospasm is mostly bilateral. Other conditions which can be confused with hemifacial spasms are facial tics, facial myokymia, hemimasticatory spasm. If the neurological examination is otherwise normal, then no further tests are done. However, if patients have focal abnormalities on neurological examination, then MRI is useful. MRI should be obtained with special attention to the brain stem structures.

TREATMENT: The treatment of choices for hemifacial spasm is  Botulinum toxin(BOTOX) injected intramuscularly. The effect of BOTOX usually lasts  for 3-4 months. The dosage required is very low as compare to cervical dystonia. Once the effect  of BOTOX wears off, the injections have to be repeated again. If the excessive dose of BOTOX is injected, patients may develop drooping of eyelids or face but this usually recovers in a few weeks.

 Surgical treatment is used very rarely. Medications such as carbamazepine may be effective in some cases.