[A case of juvenile hemifacial spasm, successfully treated by microvascular decompression].

A 16-year-old girl had an episode of intermittent involuntary spasm of the right inferior orbicularis oculi muscle at the age of 12. In the following years the right orbicularis oris muscle and platysma were unilaterally and progressively involved in the spasms and with increasing frequency. Medical treatment with minor transquilizer was not effective. She was referred to our department at the age of 16. CT and MRI revealed no abnormality. Angiographical study revealed that the right PICA (posterior inferior cerebellar artery) was tourtously coming off from a relatively high portion of the right vertebral artery. The trunk of the right AICA (anterior inferior cerebellar artery) was not able to be identified. Although the onset of this condition was unusually early, the clinical course and symptoms of hemifacial spasm were so clearly typical that she underwent microvascular decompression surgery on July 26, 1988, at the age of 16. During the operation an upward looping PICA was found crossing and tightly compressing the exit zone of the right facial nerve. The offending artery seemed to be elastic without significant atherosclerotic change. The arterial loop was carefully dissected and replaced with two pieces of sponge prosthesis between the artery and the surface of brain stem. Her hemifacial spasm completely disappeared post-operatively. No recurrence has been noted for over one year in the follow-up observation. Hemifacial spasm is subacutely or chronically a progressive disorder of facial involuntary movement. The arterial compression in the exit zone of the facial nerve is said to be the cause of the disorder and microvascular decompression has been indicated for it since a little before the beginning of this decade.(ABSTRACT TRUNCATED AT 250 WORDS)