The term hemifacial spasm (HFS) refers to involuntary muscle contraction (spasm) on one side (hemi) of the face. HFS is also known as tic convulsif.
One common cause of HFS is a malfunction in the seventh cranial nerve, which is the facial nerve controlling movement of facial muscles. This malfunction can result from an injury or tumor, or Bell's palsy.
Most often, a blood vessel is pressing on the facial nerve. The nerve misfires, and the muscles in the face experience spasm. In many other cases, the source of the disorder is unknown.
Women are more often affected by HFS than men, at middle-age or older.
The most common first symptom will be the twitching of an eyelid, possibly resulting in that eye being permanently closed. Twitching may traverse into the muscles in the cheek, the jaw and neck.
In a small number of cases, symptoms may begin near the chin and work their way upward. These contractions can cause the jaw to open, lips to be distorted, or the tongue to stick out.
In severe cases, all muscles on that side of the face spasm constantly. The individual experiences tonus phenomena, which might be described as a charlie horse of the face. The side of the face seizes up, with the eye closed, cheek contracting, and the jaw clenched.
It is uncommon to have the spasm spread to both sides of the face.
This is not a painful condition. But having one's face twisted into a mask, and being unable to move eyes or lips, causes a myriad of problems. And having one eye refuse to open leads to numerous visual disturbances.
Since these symptoms can occur without warning at any time, this disorder is severely limiting.
Possible treatments are medication, ablative therapy, and surgery.
Medication like muscle relaxants and sedatives have proven to have limited success.
Ablative therapy is injection of botulinum toxin (botox) into the muscles. This weakens facial muscles, and may relieve spasm. Injections may need to be repeated after a few months.
Possible side effects are too much weakness in facial muscles, irritation of the eye and a drooping lid.