Hemifacial spasm (HFS) is a rare neuromuscular disease which is characterized by involuntary and irregular muscle contraction or spasms generally on one side of the face. Facial muscles are commonly controlled by the facial nerve which is called the seventh cranial nerve; the facial nerve originates at the brainstem and exits out of the skull right below the ear.
Although not commonly seen, this is a tremendously critical disease that if untreated or properly managed can be severely permanent.
This unpleasant disease commonly takes two forms: typical and atypical. The typical form generates twitching which can usually start in the lower eye lid in the oculi muscle. When time progresses, it will spread to the entire lid, the muscles around the lips and cheekbone area.
There is a revers process regarding the twitching and this occurs in an atypical Hemifacial spasm. Twitching will start in the muscles around the lips, the muscle in the cheekbone area (lower face), then will progress up to the eyelid as time goes by. Typical form is the most common diagnoses, with the atypical form being seen in about 3% of patients suffering from Hemifacial spasms.
Hemifacial spasms generally occur more frequently in middle-aged or elderly women, but can be seen in both men and women. This disease may be caused by a facial nerve injury, no apparent cause, or a tumor. For more information about Hemifacial spasms, treatment and surgery check out this site.