Hemifacial spasm is a condition that involves involuntary muscle contractions that take place on only one side of the face. It often begins with occasional twitching in an eyelid that may progress to a complete closure of the affected eye. The muscle spasms usually spread down to the lower portion of that side of the face, and may produce contortions such as a sideways pulling of the mouth. Every muscle on the affected side of the face may start to experience increasingly frequent spasms over time.
Causes of Hemifacial Spasm
The most common cause of hemifacial spasm is excessive pressure on a facial nerve where it exits the brainstem. In other cases, the disorder may be due to a tumor in the region. Sometimes, no obvious cause may be found.
Many patients with hemifacial spasm are successfully treated with botulinum toxin injections. Used medically to block nerve signals, these injections are administered directly into the affected muscles to prevent them from contracting. If the botulinum toxin injections are not effective, the patient may require a surgical procedure known as microvascular decompression, which is performed to alleviate the pressure on the facial nerve.