Myoclonic spasms Hemifacial spasm 2010-07-10T04:15:33Z Hemifacial spasm presents in the fifth or sixth decade of life, and is almost always unilateral. An attack usually begins with brief clonic movements of the orbicularis oculi and spreads over years to other facial muscles. Hemifacial spasm is often the result of chronic irritation of the facial nerve or nucleus. SNOMEDCT_US:13753008 HP:0010828 Spasms on one side of the face UMLS:C0278152 Intermittent clonic or tonic contraction of muscles supplied by facial nerve. Muscles are relaxed in between contractions. Hemifacial spasms