Blepharospasm and hemifacial spasm are terms which describe uncontrolled, forceful blinking and/or facial movements. They are caused by abnormal nerve impulses to these muscles. In the case of blepharospasm, the nerve impulses may originate in a part of the brain called the basal ganglia, but the cause is unknown. In the case of hemifacial spasm, the cause is thought to be an irritation of the seventh cranial nerve, sometimes from a nearby blood vessel, which causes the nerve on one side to fire repetitively.
What are the symptoms?
The movement disorder may produce blinking, winking, or squinting. Movements can range in severity. They may be mild and go unnoticed. On the other hand, severe uncontrolled eye closure can interfere significantly with activities of daily living, like driving and reading. Some patients notice that certain activities trigger blepharospasm more than others. Light sensitivity is common. In the case of hemifacial spasm, that side of the face may be weak compared to the other.
What is the treatment?
The most common and effective therapy for both blepharospasm and hemifacial spasm are intramuscular injections of botulinum toxin (brand name Botox, Xeomin, or Dysport). Botulinum toxin weakens the muscles for about 3 months, making the involuntary movements more tolerable. In the case of Blepharospasm, medications are sometimes recommended, but are less consistent in their effectiveness compared with botulinum toxin.
In both conditions surgery has a limited role. In the case of blepharospasm, the orbicularis muscle (the muscle that closes the eye) can be partially removed. In the case of hemifacial spasm, if the seventh nerve irritant (like a blood vessel) can be identified, neurosurgery can be considered to separate the structures.
How does Botulinum Toxin A work and what are the side effects?
Botulinum toxin is what causes a type of food poisoning called botulism. Botulinum toxin weakens muscles. Physicians have reported good results using very small amounts of this toxin (too small to cause botulism) to treat various movement disorders. When small amounts of the toxin are injected into the eyelid or facial muscles, the abnormal movements greatly diminish. The effectiveness of the toxin is temporary, typically wearing off in about 3 months. Therefore, repeat injections are common.
Side effects of Botulinum Toxin may include a droopy lid, double vision, dry eye from incomplete lid closure, and tearing. The side effects occur when the toxin inadvertently affects a nearby muscle, or when the weakening effect on the intended target is too strong. The side effects typically wear off with time, just as the toxin does. The same dose of botulinum toxin can cause different responses in different people. On occasion people will notice that some botulinum treatments work better others.
More information on this condition can be found at the National Eye Institute’s website, the North American Neuro-Ophthalmology Society website, or the Benign Essential Blepharospasm Research Foundation’s website.