Intraoperative Lateral Spread Response Research Articles

Predicting long-term outcomes after microvascular decompression for hemifacial spasm according to lateral spread response and immediate postoperative outcomes: a cohort study.

Microvascular decompression (MVD) is a well-established and highly effective treatment option for hemifacial spasm (HFS). Lateral spread response (LSR) has been used as an intraoperative indicator of HFS resolution, with controversial reliability. The purpose of this study was to determine long-term outcomes of MVD for HFS and the role of LSR and other preoperative predictors. The authors conducted a cohort study of all patients treated with MVD for HFS at a single institution from January 1, 1998, to December 31, 2019. In addition to a retrospective chart review, all patients were contacted at the time of the study to provide informed consent and responded to a telephone survey to ascertain their current disease and medication status. Patients with at least 12 months of postoperative follow-up were included. Statistical testing included a Student t-test, Fisher's exact test, logistic regression, and Cox proportional hazards analysis. One hundred nineteen patients met study criteria; 41 (34%) had at least 10 years of clinical follow-up. HFS fully resolved in 93 (78%), symptoms subjectively improved in 11 (9%) and were unchanged in 15 (13%). Immediate postoperative HFS status did not correlate with long-term outcome (p = 0.13). Changes in LSR were not associated with outcome. Patients receiving neuromodulating agents had significantly longer preoperative duration of symptoms and were more likely to show persistent LSR intraoperatively. HFS recurrence was associated with younger age at the time of surgery but not with intraoperative LSR resolution. This study demonstrated that MVD for HFS is highly effective for most patients. Neither intraoperative LSR change nor immediate postoperative status was predictive of long-term outcomes.

Prognostic Value of Lateral Spread Response Recorded 1 Month After Microvascular Decompression for the Treatment of Hemifacial Spasm.

The predictive value of intraoperative disappearance of the lateral spread response (LSR) during microvascular decompression surgery for hemifacial spasm treatment is unclear. Studies evaluating the clinical implications of the LSR recorded during the postoperative period are also limited. To analyze the LSR 1 month postoperatively and to evaluate its prognostic value until 1 year postsurgery. In total, 883 patients who underwent microvascular decompression between 2016 and 2018 were included. LSR was recorded preoperatively, intraoperatively before decompression, intraoperatively after decompression, and 1 month postoperatively. The outcomes were evaluated at 1 week, 1 month, and 1 year postoperatively. The presence of preoperative and intraoperative LSR after decompression did not predict the postoperative outcome at 1 year. In 246 patients (27.9%), the postoperative LSR at 1 month was not identical to that recorded intraoperatively after decompression. Postoperative LSR at 1 month was associated with a worse outcome at 1 month (P < .0001) and 1 year (P = .0002) postoperatively. Patients with residual symptoms and a LSR 1 month postoperatively were more likely to show residual symptoms 1 year postoperatively, with a positive predictive value of 50.7%. Unlike the intraoperative LSR, the LSR at 1 month postoperatively showed prognostic value in predicting 1-year postoperative outcomes and was useful for identifying patients with a high risk of unfavorable outcomes. Thus, confirming the presence of postoperative LSR is necessary.

The novel prognostic value of postoperative follow-up lateral spread response after microvascular decompression for hemifacial spasm.

The lateral spread response (LSR) is an aberrant electrophysiological response in which a stimulus on one branch of the facial nerve spills over to other branches of the nerve, which can be captured by electrodes near each branch. The authors performed this study to evaluate the prognostic value of the follow-up LSR with a sufficient time interval from intraoperative LSR (IO-LSR) after microvascular decompression (MVD) for hemifacial spasm (HFS), excluding the interference of various intraoperative situations. A total of 247 patients treated with MVD for HFS between June 2011 and March 2019 were enrolled in this study. The IO-LSR was routinely evaluated in all patients. The LSR was checked again on postoperative day (POD) 2 after surgery (POD2-LSR). A total of 228 patients (92.3%) were considered cured at the last clinical follow-up. The IO-LSR disappeared in 189 patients (76.5%), and among them, 181 patients (95.8%) were cured 1 year after surgery. The POD2-LSR disappeared in 193 patients (78.1%), and 185 patients (95.9%) among them were cured. Among the 189 patients in which the IO-LSR disappeared, the POD2-LSR reappeared in 26 patients (13.8%). In contrast, the POD2-LSR disappeared in 30 (51.7%) of 58 patients for whom the IO-LSR continued at the end of surgery. When classified into groups according to the status of the IO-LSR and POD2-LSR, in the group of patients in whom both LSRs disappeared, the cure rate was 98.2%, which was significantly higher than that of the other 3 groups (p < 0.05, Cochran-Armitage trend test). The use of both LSRs was found to be significantly associated with better predictability (p < 0.05, McNemar's test). Postoperative follow-up LSR examination may be beneficial in predicting clinical outcomes after MVD for HFS, especially when considered together with IO-LSR.

The Utility of Intraoperative Lateral Spread Recording in Microvascular Decompression for Hemifacial Spasm: A Systematic Review and Meta-Analysis.

Microvascular decompression (MVD) is the surgical treatment of choice for hemifacial spasm (HFS). During MVD, monitoring of the abnormal lateral spread response (LSR), an evoked response to facial nerve stimulation, has been traditionally used to monitor adequacy of cranial nerve (CN) VII decompression. To assess the utility of LSR monitoring in predicting spasm-free status after MVD postoperatively. We searched PubMed, Web of Science, and Embase for relevant publications. We included studies reporting on intraoperative LSR monitoring during MVD for HFS and spasm-free status following the procedure. Sensitivity of LSR, specificity, diagnostic odds ratio, and positive predictive value were calculated. From 148 studies, 26 studies with 7479 patients were ultimately included in this meta-analysis. The final intraoperative LSR status predicted the clinical outcome of MVD with the following specificities and sensitivities: 89% (0.83- 0.93) and 40% (0.30- 0.51) at discharge, 90% (0.84-0.94) and 41% (0.29-0.53) at 3 mo, 89% (0.83-0.93) and 40% (0.30-0.51) at 1 yr. When LSR persisted after MVD, the probability (95% CI) for HFS persistence was 47.8% (0.33-0.63) at discharge, 40.8% (0.23-0.61) at 3 mo, and 24.4% (0.13-0.41) at 1 yr. However, when LSR resolved, the probability for HFS persistence was 7.3% at discharge, 4.2% at 3 mo, and 4.0% at 1 yr. Intraoperative LSR monitoring has high specificity but modest sensitivity in predicting the spasm-free status following MVD. Persistence of LSR carries high risk for immediate and long-term facial spasm persistence. Therefore, adequacy of decompression should be thoroughly investigated before closing in cases where intraoperative LSR persists.

Flat-shaped posterior cranial fossa was associated with poor outcomes of microvascular decompression for primary hemifacial spasm

Numerous factors have been investigated on affecting the outcomes of primary hemifacial spasm (HFS) after microvascular decompression (MVD). It is well established that anatomical differences of the posterior cranial fossa (PCF) plays an important role in the occurrence of HFS. However, it is still not clear whether morphological characteristics of PCF affect the surgical outcomes of HFS after MVD. Our study aims to investigate the prognostic factors for surgical outcomes of MVD for primary HFS, with a particular focus on the morphological characteristics of PCF. Between January 2014 and November 2017, a total of 152 HFS patients who underwent MVD treatment in our department were included in this study. The clinical data were retrospectively reviewed. The outcomes of MVD were classified into success and failure groups according to the short- and long-term postoperative responses. Particularly, we established an ellipsoid model for PCF. The related length (Y), width (X) and height (Z) of the PCF were measured and the volume of PCF was calculated employing a formula of [Formula: see text]XYZ. The relationship between PCF volume and surgical outcomes was statistically analysed. The severity of neurovascular compression (NVC) (p = 0.010), type of NVC (p = 0.001) and lateral spread response (LSR) (p < 0.0001) significantly influenced the long-term surgical outcomes of MVD for primary HFS. In particular, for the first time, we demonstrated that a flat-shaped PCF was associated with poor long-term outcome and postoperative recurrence. Our current study suggests that mild NVC, small vessel compression, intraoperative LSR persistence and flat-shaped PCF are independent factors predicting poor prognosis of MVD for primary HFS.

Predictive value of intraoperative blink reflex monitoring for surgical outcome during microvascular decompression for hemifacial spasm

ObjectiveTo investigate the prognostic and predictive value of intraoperative blink reflex (BR) monitoring during microvascular decompression (MVD) for hemifacial spasm (HFS). MethodsWe retrospectively reviewed 41 patients with HFS undergoing MVD with intraoperative BR and lateral spread response (LSR) monitoring. Facial spasm was evaluated for six months postoperatively. ResultsThe BR resolved in 38 patients and persisted in three after MVD. For patients who exhibited BR resolution, 1-day, 1-month, and 6-month follow-ups revealed that 35 (92.1%), 35 (92.1%), and 38 (100%) patients had spasm resolution, respectively. However, of the three patients with persistent BR, one (33.3%), one (33.3%), and zero (0%) patients exhibited spasm resolution at the three corresponding follow-ups. We found a statistically significant difference in spasm resolution between the persistent and resolved BR groups at six months postoperatively. A comparison between intraoperative BR and LSR monitoring revealed that BR was a better predictor of clinical outcomes. ConclusionsIntraoperative BR monitoring is a potentially useful tool to help facilitate an adequate decompression and is a reliable prognostic predictor of surgical outcome. SignificanceThis study is the first to document the relationship between intraoperative BR monitoring and surgical outcome in patients with HFS.

Prognostic value of lateral spread response during microvascular decompression for hemifacial spasm.

ObjectiveThis study aimed to investigate the prognostic value of the lateral spread response (LSR) for predicting surgical outcomes following microvascular decompression (MVD) in patients with hemifacial spasm.MethodsSeventy-three patients with hemifacial spasm underwent MVD with intraoperative LSR monitoring. Surgical outcomes were evaluated 1 week and 1 year after MVD and correlations between LSR characteristics and surgical outcomes were analyzed.ResultsThe LSR disappeared completely in 61 patients during surgery (Group A; prior to insertion of Teflon felt pledgets in 11, after insertion of pledgets in 50), disappeared partially in nine patients (Group B), and remained unchanged in three patients (Group C). Fifty-five patients showed short-term and 61 patients showed long-term clinical cures during the follow-up period. The short-term and long-term cure rates were significantly higher in Group A than in Group C. There was no correlation between the time of complete LSR disappearance and surgical outcomes.ConclusionsDisappearance of the LSR during MVD is correlated with the surgical outcomes. Intraoperative LSR monitoring is a reliable approach for predicting the prognosis of hemifacial spasm following MVD, but the time at which LSR disappears is not a prognostic indicator.

Platform Session – Evoked potentials & NIOM: Prognostic value of intra- and extra-operative lateral spread responses in microvascular decompression surgeries of hemifacial spasm

Introduction Lateral spread response is observed in patients with hemifacial spasm (HFS) by eletrically stimulating one branch of the facial nerve activates facial muscles innervated by other branches of the facial nerve by electromyography. Nowadays, LSR has been used to confirm adequacy of microvascular decompression (MVD). The aim of this study was to evaluate the prognostic value of intra- and extra-operative lateral spread response (LSR) in microvascular decompression (MVD) surgeries of hemifacial spasm (HFS). Methods A retrospective review was made of consecutive 25 patients who underwent continuous intraoperative monitoring during MVD. LSR and continuous electromyography were monitored in the frontalis, orbicularis oculi, and mentalis muscles. Extra-operative LSRs were done pre- and postoperatively. The neurological status of each patient was evaluated before and immediately after surgery, on discharge, and at 3 months after surgery. Results Intraoperative neurophysiologic monitorings were successful in all patients. On admission and discharge, extra-operative LSR recordings were done in 23 patients. Twenty-one patients completed a follow- up evaluation. In 17, the intraoperative LSRs disappeared during surgery. In 5, the intraoperative LSRs were absent before incision and remained the same until the end of surgery. In one, the intraoperative LSR were present before incision and persisted despite MVD. For extra-operative LSRs, they disappeared after surgery in 10. LSRs were absent before and after surgery in 7. In 6, LSRs were present before surgery and persisted after MVD. For 5, intraoperative LSRs disappeared during surgery but extra-operative LSRs were persisted despite adequate MVD. In one, intraoperative LSRs were absent before incision and remained during the surgery. But extra-operative LSRs were present before surgery and disappeared after adequate MVD. Statistically, the extra-operative disappearance of LSR was correlated with the HFS relief in 4 days after surgery and the 3-month follow up period. (P = 0.049 and 0.044). However, the intaroperative disapearance of LSR was not. Conclusion In our study, extra-operative LSR monitoring may be more predictive of the surgical outcome compared with intraoperative LSR during the 3-month follow up.

Microvascular decompression for hemifacial spasm: can intraoperative lateral spread response monitoring improve surgical efficacy?

OBJECTIVE The purpose of this study was to evaluate whether intraoperative monitoring of lateral spread response (LSR) improves the efficacy of microvascular decompression (MVD) for hemifacial spasm (HFS). METHODS In this prospective study, patients undergoing MVD for HFS were assigned to one of 2 groups, Group A (MVD with intraoperative LSR monitoring) or Group B (MVD without LSR monitoring). Clinical outcome at 12 months after surgery was assessed through telephone survey. Data analysis was performed to investigate the effect of intraoperative LSR monitoring on efficacy of MVD. RESULTS A total of 283 patients were enrolled in the study, 145 in Group A and 138 in Group B. There was no statistically significant difference between the 2 groups with respect to the percentage of patients who had spasm relief at either 1 week (Group A 87.59% vs Group B 83.33%; p = 0.317) or 1 year (93.1% vs 94.2%; p = 0.809) after surgery. A clear-cut elimination of LSR during surgery was observed in 131 (90.34%) of 145 patients; LSR persisted in 14 patients (9.66%) at the end of the surgical procedure. Disappearance of LSR correlated with spasm-free status at 1 week postoperatively (p = 0.017) but not at 1 year postoperatively (p = 0.249). CONCLUSIONS Intraoperative LSR monitoring does not appear to provide significant benefit with respect to the outcome of MVD for HFS in skilled hands. Persistence of LSR does not always correlate with poor outcome, and LSR elimination should not be pursued in all patients after verification of complete decompression.

Persistent hemifacial spasm after microvascular decompression: a risk assessment model

Objective: Microvascular decompression (MVD) for hemifacial spasm (HFS) provides resolution of disabling symptoms such as eyelid twitching and muscle contractions of the entire hemiface. The primary aim of this study was to evaluate the predictive value of patient demographics and spasm characteristics on long-term outcomes, with or without intraoperative lateral spread response (LSR) as an additional variable in a risk assessment model.Methods: A retrospective study was undertaken to evaluate the associations of pre-operative patient characteristics, as well as intraoperative LSR and need for a staged procedure on the presence of persistent or recurrent HFS at the time of hospital discharge and at follow-up. A risk assessment model was constructed with the inclusion of six clinically or statistically significant variables from the univariate analyses. A receiving operator characteristic curve was generated, and area under the curve was calculated to determine the strength of the predictive model.Results: A risk assessment model was first created consisting of significant pre-operative variables (Model 1) (age >50, female gender, history of botulinum toxin use, platysma muscle involvement). This model demonstrated borderline predictive value for persistent spasm at discharge (AUC .60; p=.045) and fair predictive value at follow-up (AUC .75; p=.001). Intraoperative variables (e.g. LSR persistence) demonstrated little additive value (Model 2) (AUC .67). Patients with a higher risk score (three or greater) demonstrated greater odds of persistent HFS at the time of discharge (OR 1.5 [95%CI 1.16–1.97]; p=.035), as well as greater odds of persistent or recurrent spasm at the time of follow-up (OR 3.0 [95%CI 1.52–5.95]; p=.002)Conclusions: A risk assessment model consisting of pre-operative clinical characteristics is useful in prognosticating HFS persistence at follow-up.

Good Surgical Outcomes of Hemifacial Spasm Patients with Obvious Facial Nerve Indentation and Color Change

Hemifacial spasm results from vascular compression of the facial nerve. It remains controversial whether severe compression and subsequent nerve indentation predict a good or a poor surgical outcome. Here, to illustrate the relationship between the degree of neurovascular compression and surgical outcome, we conducted a retrospective case-cohort study focused on patients whose facial nerve was seriously compressed. This study included 2 groups. The nerve-indentation group included 48 patients with hemifacial spasm whose facial nerves had obvious indentation and color change at the site of neurovascular conflict. The control group included 48 randomly selected patients with hemifacial spasm without facial nerve indentation or color change who were surgically treated by the same team during the same period. The surgical findings, intraoperative lateral spread response results, and clinical outcomes were compared. Single-vessel compression was found more frequently in the nerve-indentation group (87.5%) than in the control group (60.4%, P < 0.05). The lateral spread response (LSR) resolution rate of the nerve-indentation group was 91.7%, and that of the control group was 87.5% (P > 0.05). The rates at which the microvascular decompression procedure was successful were equal in the nerve-indentation and the control groups (93.8% vs. 91.7%, P > 0.05). Severe vascular compression and subsequent nerve indentation were correlated with a greater possibility of single compression and a lower incidence of multiple neurovascular conflicts in patients with hemifacial spasm, making the microvascular decompression procedure more accurate and easier. Therefore nerve indentation might predict good surgical outcomes.

Effects of botulinum toxin on electrophysiological monitoring the lateral spread response in the facial nerve microvascular decompression surgery

Objective To investigate the effects of facial injecting botulinum toxin on electrophysiological monitoring indicator lateral spread response (LSR) in patients with hemifacial spasm in microvascular decompression surgery. Methods Ninety patients with facial spasm underwent microvascular decompression surgery in Guangdong No 2 Provincial People's Hospital from July 2013 to December 2014 were enrolled retrospectively. They were divided into either a botulinum toxin group (n=18) or a non-botulinum toxin group (n=72) according to whether they injected botulinum toxin or not. The effect of botulinum toxin on the changes of intraoperative LSR and the role of LSR changes in prognostic evaluation were observed. Results The mean LSR latency of the zygomatic branch in the botulinum toxin group was 11.4±2.1 ms, and in the non-botulinum toxin group was 9.3±1.4 ms. There was significant difference (P 0.05). The LSR amplitude of the zygomatic branch in botulinum toxin group was 116.1±61.1 μV, and in mandibular branch was 116.1±54.5 μV; the zygomatic branch was 125.9±52.1 μV, and the mandibular branch was 125.9±52.1 μV in the non-botulinum toxin group. There was no significant difference between the 2 groups. After implantation of shims, the LSR disappear rates of zygomatic branchs, and mandibular branch were 16/18and 17/18 respectively in the botulinum toxin group; the zygomatic branch disappear rate in the non-botulinum toxin group was 90% (65/72) and that in the mandibular branch was 96% (69/72). There was no significant difference between the 2 groups (P>0.05). The sensitivity of the disappearance of zygomatic branch LSR for prognostic judgment in the botulinum toxin group was 94% (15/16), and in the non-botulinum toxin group was 98% (64/65). There was significant difference (P<0.05). The mandibular branch LSR, and the sensitivities of both zygomatic branch and mandibular branch disappeared simultaneously for prognostic judgment in the botulinum toxin group were 94% (16/17) and 94% (15/16) respectively; and in the non-botulinum toxin group were 92% (64/69) and 96% (59/61) respectively. There was no significant difference between the 2 groups. Conclusions Botulinum toxin has influence on intraoperative LSR. It is expressed as the prolonged LSR latency of zygomatic branch. The way of monitoring with mandibular branch or in combination with zygomatic branch LSR may be better than simply monitoring zygomatic branch LSR. Key words: Microvascular decompression surgery; Nervous system physiological processes; Hemifacial spasm; Botulinum toxins; Lateral spread response

Effects of partial neuromuscular blockade on lateral spread response monitoring during microvascular decompression surgery

ObjectiveWe evaluated the effect of partial neuromuscular blockade (NMB) and no NMB on successful intraoperative monitoring of the lateral spread response (LSR) during microvascular decompression (MVD) surgery. MethodsPatients were randomly allocated into one of three groups: the TOF group, the NMB was targeted to maintain two counts of train-of-four (TOF); the T1 group, maintain the T1/Tc (T1: amplitude of first twitch, Tc: amplitude of baseline twitch) ratio at 50%; and the N group, no relaxants after tracheal intubation. Successful LSR monitoring was defined as effective baseline establishment and maintenance of the LSR until dural opening. ResultsThe success rate of LSR monitoring was significantly lower in the TOF group. But, there was no significant difference between T1 and N. The detection rate of spontaneous free-run electromyography (EMG) activity was significantly higher in the N group compared with the TOF and T1 groups. ConclusionsPartial NMB with a target of T1/Tc ratio at 50% allows good recording of LSR with same outcome as surgery without NMB, and reduced spontaneous EMG activity. SignificanceWe suggested the availability of partial NMB for intraoperative LSR monitoring.

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

ObjectiveThe 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.MethodsContinuous 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.ResultsIntra-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).ConclusionIt 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.

Microvascular Decompression for Hemifacial Spasm: Evaluating Outcome Prognosticators Including the Value of Intraoperative Lateral Spread Response Monitoring and Clinical Characteristics in 293 Patients

Hemifacial spasm is a socially disabling condition that manifests as intermittent involuntary twitching of the eyelid and progresses to muscle contractions of the entire hemiface. Patients receiving microvascular decompression of the facial nerve demonstrate an abnormal lateral spread response (LSR) in peripheral branches during facial electromyography. The authors retrospectively evaluate the prognostic value of preoperative clinical characteristics and the efficacy of intraoperative monitoring in predicting short- and long-term relief after microvascular decompression for hemifacial spasm. Microvascular decompression was performed in 293 patients with hemifacial spasm, and LSR was recorded during intraoperative facial electromyography monitoring. In 259 (87.7%) of the 293 patients, the LSR was attainable. Patient outcome was evaluated on the basis of whether the LSR disappeared or persisted after decompression. The mean follow-up period was 54.5 months (range, 9-102 months). A total of 88.0% of patients experienced immediate postoperative relief of spasm; 90.8% had relief at discharge, and 92.3% had relief at follow-up. Preoperative facial weakness and platysmal spasm correlated with persistent postoperative spasm, with similar trends at follow-up. In 207 patients, the LSR disappeared intraoperatively after decompression (group I), and in the remaining 52 patients, the LSR persisted intraoperatively despite decompression (group II). There was a significant difference in spasm relief between both groups within 24 hours of surgery (94.7% vs. 67.3%) (P < 0.0001) and at discharge (94.2% vs. 76.9%) (P = 0.001), but not at follow-up (93.3% vs. 94.4%) (P = 1.000). Multivariate logistic regression analysis demonstrated independent predictability of residual LSR for present spasm within 24 hours of surgery and at discharge but not at follow-up. Facial electromyography monitoring of the LSR during microvascular decompression is an effective tool in ensuring a complete decompression with long-lasting effects. Although LSR results predict short-term outcomes, long-term outcomes are not as reliant on LSR activity.

A reappraisal of the value of lateral spread response monitoring in the treatment of hemifacial spasm by microvascular decompression

Background:Lateral spread response (LSR) to the electrical stimulation of a facial nerve branch is a specific electrophysiological feature of primary hemifacial spasm (HFS). The curative treatment of HFS is based...

Prognostic value of intra-operative lateral spread response monitoring during microvascular decompression in patients with hemifacial spasm

Hemifacial spasm (HFS) has characteristic and specific electrophysiological features, primarily the lateral spread response (LSR). The aim of this study was to evaluate the correlation between changes in the lateral spread response during microvascular decompression (MVD) and the clinical outcome after MVD. Seventy-two patients with HFS who were treated with MVD were included in this study. Intra-operative facial electromyography (EMG) was performed and brainstem auditory evoked potentials were monitored. In 32 (44.4%) patients, the LSR persisted after MVD. Among these 32 patients, 11 had mild HFS at discharge and six had mild HFS at the 6 month follow up. Out of the 40 patients in whom the LSR disappeared intra-operatively after MVD, five had mild HFS at discharge and four had mild HFS at the 6-moth follow up. The clinical outcome of HFS after MVD does not always correlate with intra-operative EMG abnormality. Therefore, the prognostic value of intra-operative LSR monitoring with respect to long-term results is questionable.