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Thursday, February 17, 2011

CLONAL FACIAL (HEMIFACIAL) SPASM

This disorder presents mostly after middle age.

Clinical features
Symptoms usually start with intermittent twitching around the aye. Over the course of months or years, clonic twitches increase in frequency and severity so that the eye may close for a few seconds at a time, and gradually the movements begin to affect the lower face.
 The spasms are intermittent, sometimes being more prominent during talking and eating or when the patient is under stress. Occasionally sufferers report transient dulling hearing on the affected side during a facial spasm- presumably due to stapedius contraction. Examination reveals, in addition to the spasms, mild weakness of the affected musculature.

Investigation
Facial nerve conduction studies are usually normal or show only minor defects of distal conduction and the blink reflex. EMG recording shows bursts of rapid motor unit firing during the spasms, with periods of silence interposed. The pathophysiology is now believed to be due to an aberrant loop of artery irritating the facial nerve as it emerges from the pons-similar the mechanism postulated for trigeminal neuralgia.

Management
Treatment with carbamazepine or phenytoin as for trigeminal neuralgia may help reduce the frequency and severity of the spasms, but is often disappointing. If the disorder is severe and disfiguring, posterior fossa exploration and micro vascular decompression may be justifiable, but the risk of this in an elderly patient must be balanced against the benign nature of the condition. Injections of botinulinum toxin in to the affected muscles may control symptoms for several months, and is becoming an established treatment.

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