Surgery for hemifacial spasm

Hemifacial spasm (HFS), a syndrome of unilateral facial nerve hyperactive dysfunction, is a severe and disabling condition that causes impairments in the quality of life [1]. The spasms are characterized by slight intermittent twitching of a single facial muscle that gradually becomes more intense and occurs with greater frequency, later spreading to involve the other muscles of facial expression. Ultimately, the patient may develop prolonged contractions of all the involved muscles causing severe, disfiguring grimacing with partial closure of the eye and drawing up of the corner of the mouth, the so-called tonus phenomenon [2]. Typical and atypical variations of the disorder exist. In typical HFS, spasms begin insidiously in the orbicularis oculi muscle and spread over time to the muscles of the face with variable involvement of the frontalis and platysma muscles. Conversely, in atypical HFS, spasms begin insidiously in the muscles of the lower face and spread to the orbicularis oculi muscles over time. Typical HFS occurs much more frequently than atypical HFS [3]. The best available data suggest that the prevalence rate of HFS is 10 patients per 100,000 in the population of the United States and Norway [4, 5].