Overview of Hemifacial Spasm (HFS)
Hemifacial spasm (HFS) is a syndrome of one-sided facial twitching that cannot be controlled by the patient. In affected patients, this usually begins in middle age and comes and goes, but over time can become nearly constant. The movement of the face is controlled by the facial nerve on the same side. The facial nerve arises from the brain stem in the posterior compartment of the brain (posterior fossa) in a region called the
cerebellopontine angle (CPA).
Symptoms of Hemifacial Spasm (HFS)
HFS is characterized by intermittent uncontrollable twitching of facial muscles on one side that usually begins around the eye. Initially there can be isolated periods of twitching that over time become more frequent and can progress to almost continual facial spasms. The twitching occurs during sleep and can increase during times of stress or fatigue. Between spasms the face functions normally and, aside from the twitching, there are no other symptoms except an occasional complaint of an aching sensation in advanced cases.
Causes of Hemifacial Spasm (HFS)
Almost all cases of HFS are associated with the finding of a blood vessel compressing the facial nerve where it arises from the brain stem (root entry zone) at the junction of the medulla (bottom part of the brain stem) and pons (middle part of the brain stem). Either an artery or vein or both can be found compressing the nerve but arteries are most common. In extremely rare cases no blood vessel is found and the cause of the HFS is not known.
Diagnosis of Hemifacial Spasm (HFS)
The diagnosis of hemifacial spasm is primarily based on a careful analysis of the patient’s symptoms and examination of the patient to confirm the location of the facial twitching. MR imaging with special techniques to visualize blood vessels are routinely performed to rule out the rare presence of a tumor that can contribute to the syndrome. While a blood vessel can often be seen in the vicinity of the facial nerve that corresponds to the side of the spasms, this is not helpful to make the diagnosis or guide decisions regarding surgery because often the vessel is not clearly seen. Despite the availability of modern imaging studies, HFS is most accurately diagnosed based on the patient’s symptoms, history and examination. Rarely, a test of muscle activity called an electromyogram (EMG) can be performed for cases where the diagnosis cannot be made with certainty.
Complications of Hemifacial Spasm (HFS)
HFS presents no long-term medical or neurologic complications for the patient but the psychological impact of the disorder can have major effects on the patient’s quality of life. In addition, the spasms, when severe and frequent, can complicate some normal activities such as driving due to the constant involuntary closure of the eye.