Hemifacial spasm is a form of BEB in which spastic contractions of muscles involve an entire half of the face.  HFS often progresses to show some weakness of the face muscles on the same side, despite frequent spasms.  The spasms often are so severe that the patient completely closes one eye. It is most often due to irritation of the 7th Cranial Nerve (facial nerve) near the brainstem most often because of vascular (blood vessel) compression of the nerve, and in some cases may also be associated with decreased hearing on the affected side. Very rarely, it may occur bilaterally (on both sides of the face), but when it does, the two sides will spasm asynchronously (not together). The hallmark of this disorder is the development of spasms BEFORE any weakness is apparent.

Microvascular decompression (MVD) was a surgery originally described by Dr. Peter Jannetta. This operation is directed to the cause of the problem, vascular compression, and is usually performed in the hospital, and usually requires a 2 – 3 day stay in the hospital. The goal of surgery is to move the blood vessel (artery or vein) away from the vulnerable site on the nerve and provide a pad to prevent future compression. Complications can include infection, brain fluid leak, facial weakness, hearing loss, and stroke. Successful spasm relief ranges from 79% to 95%. The difference in the groups relates in part to patients in the former group who had undergone a previous procedure. Recovery from the procedure usually takes six weeks. Patients are usually out of the hospital on the second or third postoperative day. They are fatigued, however. The spasm can persist in 44% of patients, taking up to 18 months for complete resolution. 90% of patients are spasm free by 12 weeks after surgery.