Overview

Hemifacial spasm is a nervous system disorder in which the muscles on one side of your face twitch involuntarily. Hemifacial spasm is most often caused by a blood vessel touching a facial nerve, but it may be caused by a facial nerve injury or a tumor, or it may not have a cause.

Diagnosis

To diagnose your condition, your doctor will conduct a physical examination and check for signs of hemifacial spasm. To determine the cause of your condition and develop the most appropriate treatment for your condition, imaging tests may be necessary.

Magnetic resonance imaging (MRI) uses powerful magnets and radio waves to create detailed images of your head and determine the cause of your hemifacial spasm. Your doctor may inject a contrast dye into a blood vessel (magnetic resonance angiogram) to look for any abnormal blood vessel that may be irritating the facial nerve.

Source: http://www.mayoclinic.com