What Causes

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     There are twelve pairs of cranial nerves. The seventh (VII) or facial nerve, controls all facial movements. The nerve originates from the facial nerve nucleus in the brain stem, and branches of the nerve extend to all parts of the face, including the forehead, eye, cheek, mouth, and neck. HFS is caused by hyperactivity of the facial nerve system.

The facial nerve is the seventh of twelve pairs of cranial nerves located on either side of the head.

     HFS is typically caused by a blood vessel that is pulsating against the facial nerve root, as it leaves the brain stem. This irritation causes abnormal signals to travel back to the facial nerve nucleus within the brain stem. These abnormal signals cause the nucleus to become hyperactive. The hyperactive facial nerve nucleus then sends signals to the face causing the abnormal facial movements of HFS.

     In technical terms, HFS is typically caused by neurovascular compression of the facial nerve root entry zone (peripheral pathology), and a resultant hyperactivity of the facial nerve nucleus (central pathophysiology).

In people without HFS, there is no vascular compression upon the facial nerve root exit zone.


In people with HFS, a vessel is usually found to be pulsating against the facial nerve root exit zone.

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Prepared by A. M. Kaufmann, T. Lye & M. Patel
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