Efficacy of the Disappearance of Lateral Spread Response before and after Microvascular Decompression for Predicting the Long-Term Results of Hemifacial Spasm Over Two Years

OBJECTIVE: The purpose of this large prospective study is to assess the association between the disappearance of the lateral spread response (LSR) before and after microvascular decompression (MVD) and clinical long term results over two years following hemifacial spasm (HFS) treatment. METHODS: Continuous intra-operative monitoring during MVD was performed in 244 consecutive patients with HFS. Patients with persistent LSR after decompression (n=22, 9.0%), without LSR from the start of the surgery (n=4, 1.7%), and with re-operation (n=15, 6.1%) and follow-up loss (n=4, 1.7%) were excluded. For the statistical analysis, patients were categorized into two groups according to the disappearance of their LSR before or after MVD. RESULTS: Intra-operatively, the LSR was checked during facial electromyogram monitoring in 199 (81.5%) of the 244 patients. The mean follow-up duration was 40.9+/-6.9 months (range 25-51 months) in all the patients. Among them, the LSR disappeared after the decompression (Group A) in 128 (64.3%) patients; but in the remaining 71 (35.6%) patients, the LSR disappeared before the decompression (Group B). In the post-operative follow-up visits over more than one year, there were significant differences between the clinical outcomes of the two groups (p<0.05). CONCLUSION: It was observed that the long-term clinical outcomes of the intra-operative LSR disappearance before and after MVD were correlated. Thus, this factor may be considered a prognostic factor of HFS after MVD.

Efficacy of Intraoperative Facial Electromyographic Monitoring in Patients with Hemifacial Spasm

OBJECTIVE: Hemifacial spasm has characteristic and specific electrophysiological finding, lateral spread response(LSR). We study the correlation between change of lateral spread response during microvascular decompression(MVD) and clinical outcome after MVD. METHODS: Sixty two patients with hemifacial spasm who were treated with microvascular decompression from March 2000 to February 2003 were included in this study. The monitoring of intraoperative facial electromyography(EMG) and brain stem auditory evoked potential were performed. RESULTS: In 28 (44.7%) patients, there was persistence of lateral spread response after vascular decompression in root exit zone of facial nerve. Among these 28 patients, 9 had mild hemifacial spasm at discharge. Three out of 34 patients who had intraoperative disappearance of lateral spread response after MVD had mild hemifacial spasm. But Both groups, disappearance of LSR (Group I), and persistence (Group II) had only 2 patients with mild hemifacial spasm, and 5 patients at 3 months, respectively. CONCLUSION: Although intraoperative EMG monitoring is very useful in assessing the efficacy of MVD, the clinical outcome of MVD in patient with hemifacial spasm does not always correlate with EMG finding. The prognostic value of intraoperative LSR monitoring in the long-term results is questionable.

Electrophysiologic Study for Estimating the Clinical Severity of Hemifacial Spasm

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.