Electrophysiologic Study for Estimating the Clinical Severity of Hemifacial Spasm

ABSTRACT

BACKGROUND AND PURPOSE: Hemifacial spasm(HFS) is a chronic and often progressive disorder characterized by unilateral irregular clonic and tonic contractions of one or more muscles of facial expression. Many previous electrophysiologic studies showed characteristic features of HFS differentiating from other involuntary movements of the face. However, there has been no electrophysiologic study for estimating the clinical severity of HFS. This study was prospectively designed to evaluate the relationships between electrophysiologic findings and clinical severity of HFS. METHODS: The authors performed direct facial nerve stimulation, blink reflex, and lateral spread response in 62 patients with HFS, and compared the results of affected side with those of unaffected each other. Clinical severity was graded into seven groups (0-6) by questionnaire and confirmed by a neurologist. RESULTS: The results were as following. 1) The total number of subjects were 62, the number of patients in group 2 was 3 (4.8%), group 3 was 12 (19.3%), group 4 was 25 (40.3%), group 5 was 21 (33.9%), and group 6 was 1(1.6%). 2) The mean age was 54.5+/-9.1years old, the mean duration of the illness was 6.4+/-4.9years, male was 11(17.7%) and female was 51(82.3%), and involved sites were right in 26(41.9%) and left in 36(58.1%) patients. 3) Direct stimulation of facial nerve showed no differences between affected and unaffected sides in HFS. 4) The results of blink reflex showed more increased latencies and larger amplitudes of R1 & R2 responses in affected sides than in unaffected sides of HFS, but no differences among the groups. 5) The lateral spread responses were found in 45 of 62 (72.6%) patients by stimulation of zygomatic branch and recording in mentalis muscle, 26 of 62 (41.9%) patients by stimulation of mandibular branch and recording in orbicularis oculi muscle on affected side. 6) There was a linear correlation between the presence of lateral spread response with zygomatic or mandibular stimulation and the grade of clinical severity. CONCLUSION: We suspected that the lateral spread response was a significant electrophysiological test for estimating the clinical severity of HFS.