It is a disorder of the nervous system, in which the muscles on one side of the face move involuntarily, usually caused by a blood vessel that touches a facial nerve but can also be due to a nerve injury or a tumor, or it may have no cause.

Treatment: a) Botox injections into the affected muscles, which temporarily paralyzes those muscles. b) Other medications: anticonvulsants can relieve hemifacial spasm in some people. c) Microvascular decompression surgery, a hole is made in the skull and the dura mater is opened, to expose the facial nerve when it exits the brain stem. The blood vessel that presses on or irritates the facial nerve is located and a spongy material is placed between the nerve and the blood vessel to remove pressure on the nerve.