Hemifacial Spasm
Hemifacial spasm (HFS) is unintended twitching of one side of the face. It typically begins in the upper face or lower eyelid area, and spreads over a period of weeks to years to involve other portions of the face as well. Cosmetically, it looks strange and it is embarrassing to have part of the face twitching. Functionally, eyelid closure interferes with vision, and movement of the mouth interferes with talking and eating - and for a few patients interferes with playing of wind instruments. For some, the movement is seriously disconcerting, interfering with concentration and work.Age of Onset: Typically this comes on in middle to late adult life. It is uncommon in younger adults and very uncommon in teenagers or children. It is especially severe at younger ages, less so if onset is later in life. Prognosis: HFS usually stabilizes in a year or two after onset and does not progress thereafter. It improves in 3% of patients (3/98). HFS is not a sign of brain degeneration or of future paralysis. Four of my patients have another nerve involved with facial pain due to fifth nerve, or HFS of the face on the opposite side, due to bilateral seventh nerve irritation. On rare occasions a tumor or similar serious cause displaces the arteries to cause the spasm. In only one of 98 cases have I seen this occur, and then with other signs or symptoms. So, hemifacial spasm alone does not warrant extensive investigation, and does not mean any serious problem will ensue. Differential Diagnosis: Like many neurologic conditions, the diagnosis is made on the basis of careful clinical history and observation. Facial Tic is a habitual movement of the face. It is a patterned and repetitive movement unlike the irregular jerks of HFS, and is often bilateral. Myokymia is an irregular jerk-like movement of the eyelid. It cannot be differentiated from beginning HFS except by its usual disappearance in a few days or weeks and its lack of progression. It usually disappears permanently after Botox injection. Bell's Palsy (facial nerve paralysis) can lead to anomalous movements, but these are not twitch-like as in HFS. Distinction From Blepharospasm: Besides the brief twitches of movement, there is frequently a tonic contracture of facial muscles which can last up to 30 seconds. In this form, it is possible to confuse HFS with asymmetrical benign essential blepharospasm. Occasionally HFS is bilateral, but the movement is asymmetric and asynchronous, distinguishing it from blepharospasm, where movement is synchronous. What is HFS due to? Nerve fibers near their junction with the brain (the nerve root area) are sensitive to irritation and carry this irritation as a signal to the muscles. The facial nerve root is situated in an area crowded with other nerves and with nearby blood vessels. It is usually such a nearby blood vessel that compresses the nerve, causing the irritation and the spasms which result. Asian persons are predisposed to HFS, probably because of the physical shape of this area. As we age, the blood vessels in the brain get longer and develop a curved path rather than a straight one. This displacement of the vessels moves them to touch the nerve. Other nerves are sometimes similarly affected, causing twitching of eye muscles, throat muscles and sometimes facial pain. Nerve Damage: Weakness of the face muscles is present in about half of cases due to actual damage to nerve fibers. Abnormal sensitivity of the nerve fibers occurs as the sheath or insulation is worn off. Then activity in one nerve fiber, say, to the eyelid muscles, will be picked up by many adjacent fibers, and the whole nerve will be activated and the whole face will move. This "ephaptic conduction" is responsible for most serious and intense cases. It can even involve a small nerve branch to the middle ear muscles, causing a clicking , and a loud sound can sometimes set off the facial movement. Treatment: Mild cases can be left alone if they are not too bothersome. More severe cases respond well to local Botox injections. It is interesting that prolonged good effect up to 6-12 months, well beyond the usual duration of Botox paralysis (2-3 months) occurs in about half of cases. This prolonged effect of Botox is seen in other disorders where the nerve itself is damaged. In older persons, dosage can be very low and it is easy to over-treat. One tailors the injection site and dose to the case. Bilateral Botox to gain symmetry is helpful in unilateral HFS treatment, especially around the mouth. Decompression surgery is recommended for severe movement and for all cases age 50 or less.
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