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What is hemifacial spasm?
What causes hemifacial spasm?
How is hemifacial spasm diagnosed?
How is hemifacial spasm treated?
Hemifacial spasm is a neuromuscular disorder characterized by frequent involuntary contractions of the muscles on one side of the face. The disorder occurs in both men and women, although it more frequently affects middle-aged or elderly women. The first symptom is usually an intermittent twitching of the eyelid muscle that can lead to forced closure of the eye. The spasm may then gradually spread to involve the muscles of the lower face, which may cause the mouth to be pulled to one side. Eventually the spasms involve all of the muscles on one side of the face almost continuously.
Hemifacial spasms is usually caused by compression of the facial nerve which is the nerve that supplies strength to the muscle of the face. The source of compression in most cases is a small normal artery or vein located very close to the nerve. Over time, the pulsatile flow of blood within the artery will cause it to bump against the nerve which leads to damage to the covering around the nerve, causing it to fire abnormally which leads to contraction of the muscles that are supplies by the nerve; and this is experienced as facial spasms. Although very rare, sometimes a small tumor in the vicinity of the nerve can also lead to symptoms due to nerve compression, while other patients may experience this type of facial spasm as a result of underlying inflammation of the facial nerve, which may occur for a variety of reasons.
How is hemifacial spasm diagnosed?
The diagnosis is usually made by obtaining a thorough history and performing a complete neurological examination, which will exclude most, if not all, other possible conditions. Once the diagnosis of hemifacial spasm is made, a magnetic resonance imaging (MRI) scan of the brain should be performed in order to rule out a tumor as the cause of the spasms. While the offending blood vessel may be seen in the vicinity of the facial nerve on the MRI, this is often not the case.
How is hemifacial spasm treated?
There is a variety of treatments available for the management of hemifacial spasm which includes medical and surgical options
Anticonvulsant medications, such as carbamazepine, are the first line of treatment for hemifacial spasm. This drug can provide complete or satisfactory relief of pain in a large percentage of patients. Side effects of this medication include drowsiness, dizziness, decreased white blood cell count, and toxicity to the liver toxicity. When oral medication fails to control the spasm, several surgical and non-operative methods may be pursued, which are listed below.
Botox injection is a procedure where botulinum toxin (an muscle-paralyzing agent) is injected into the muscles of the face to temporarily paralyze them and stop the spasms. Relief of symptoms usually occurs between 3-5 days after the injection and typically lasts approximately 6 months, at which point the injections can be repeated. The effects of Botox can become increasingly less over time, and some patients complain that they continue to feel the sensation of spasms, although the spasms can not be seen. In addition, facial asymmetry and weakness can occur which are usually are transient. Overall, most patients report a highly satisfactory response.
Microvascular decompression is a surgical procedure where, under general anesthesia, a small window of bone is removed from behind the ear to gain access to the portion of the brainstem where the facial nerve is located. Then, under the microscope, the blood vessel that is pressing on the nerve is identified and moved away from the nerve, after which a soft cushion is placed between the nerve and the blood vessel in order to keep them apart. Initial relief of symptoms is seen in a large portion of patients who undergo surgery; however, recurrence rates as high as 30% have been seen. Rare complications of this procedure include facial numbness, deafness, face weakness, and cerebrospinal leak.
