Clinical impact of residual lateral spread response after adequate microvascular decompression for hemifacial spasm: A retrospective analysis

Optimal method for reliable lateral spread response monitoring during microvascular decompression surgery for hemifacial spasm

In this study, we propose an optimal method for monitoring the key electrophysiological sign, the Lateral Spread Response (LSR), during microvascular decompression (MVD) surgery for hemifacial spasm (HFS). Current monitoring methods and interpretations of LSR remain unclear, leading to potential misinterpretations and undesirable outcomes." We prospectively collected data from patients undergoing MVD for HFS, including basic demographics, clinical characteristics, and surgical outcomes. Stimulation intensity was escalated by 1 mA increments to identify the optimal range for effective LSR. We designated the threshold at which we can observe LSR as THR1 and THR2 for when LSR disappears, with high-intensity stimulation (30 mA) designated as THR30. Subsequently, we compared abnormal muscle responses (AMR) between the optimal range (between THR1 and THR2) and THR30. Additionally, we conducted an analysis to identify and assess factors associated with artifacts and their potential impact on clinical outcomes. As stimulation intensity increases, the onset latency to detect AMR was shortened. The first finding of the study was high intensity stimulation caused artifact that mimic the wave of LSR. Those artifacts were observed even after decompression thus interfere interpretation of disappearance of LSR. Analyzing the factors related to the artifact, we found the AMR detected at onset latency below 9.6 ms would be the lateral spreading artifact (LSA) rather than true LSR. To avoid false positive LSR from LSA, we should stepwise increase stimulation intensity and not to surpass the intensity that cause LSR onset latency below 10 ms.

Intraoperative Monitoring of the Facial Nerve during Microvascular Decompression for Hemifacial Spasm

This review article discusses the clinical significance of intraoperative neurophysiological monitoring (IONM), provides recommendations for monitoring protocols, and considers the interpretation of results in microvascular decompression (MVD) for hemifacial spasm (HFS). The lateral spread response (LSR) is an important monitoring parameter during MVD. It helps to identify the responsible blood vessel and confirms its thorough decompression from the facial nerve. The disappearance of the LSR during surgery is associated with favorable clinical outcomes. Standard and revised monitoring protocols and the confirmation of LSR persistence and disappearance are also discussed. The blink reflex and other facial nerve monitoring modalities, such as free-running electromyography, facial motor evoked potentials, F-waves, and the Z-L response, are further considered.

[Early results of intraoperative neurophysiological monitoring in surgical treatment of hemifacial spasm]

BACKGROUND

Neurophysiological monitoring in surgery for hemifacial spasm has been used since the 1990s, when Moller et al. demonstrated the effectiveness of intraoperative assessment of lateral spread response (LSR) regarding postoperative outcomes. Currently, there are conflicting data on effectiveness and feasibility of this technique. Widespread hemifacial spasm determines the relevance of neurophysiological monitoring in surgical treatment of these patients.

OBJECTIVE

To evaluate the effectiveness of various methods of intraoperative neurophysiological monitoring in surgical treatment of hemifacial spasm regarding early postoperative outcomes.

MATERIAL AND METHODS

The study group included 43 patients (8 men and 35 women) aged 26-68 years. We assessed severity of hemifacial spasm using the SMC Grading Scale. All patients underwent vascular decompression of the facial nerve under neurophysiological control: monitoring of transcranial motor evoked potentials from facial muscles (m. orbicularis oculi, m. orbicularis oris, m. mentalis) and recording unilateral LSR. The control group included 23 patients (4 men and 19 women) aged 29-83 years. In this group, facial nerve decompression was performed without neurophysiological control. The effect of neurophysiological monitoring on postoperative outcomes (in-hospital period and 3 postoperative months) after vascular decompression of the facial nerve was assessed using the SMC Grading Scale. We considered severity and incidence of spasms.

RESULTS

Thirty-one (72%) patients in the main group had no spasms of mimic muscles at discharge. In the control group, there were no spasms in 15 patients (65%). At the same time, there were fewer Grade I patients in the control group (12%) compared to the main group (26%). Moreover, 27 (66%) and 12 (52%) patients were free from episodes of hemifacial spasm in both groups, respectively. Patients with hemifacial spasm grade I-II comprised 29% in the main group and 34% in the control group. The number of relapses within three months increased in the control group (13%).

CONCLUSION

Intraoperative monitoring of transcranial motor evoked potentials from the facial muscles and LSR during vascular decompression of the facial nerve increases the efficiency of surgery for hemifacial spasm in early postoperative period. Less number of relapses and lower intensity of hemifacial spasm necessitate neurophysiological monitoring in neurosurgical treatment of these patients.

Advances in Intraoperative Neurophysiology During Microvascular Decompression Surgery for Hemifacial Spasm

Microvascular decompression (MVD) is a widely used surgical intervention to relieve the abnormal compression of a facial nerve caused by an artery or vein that results in hemifacial spasm (HFS). Various intraoperative neurophysiologic monitoring (ION) and mapping methodologies have been used since the 1980s, including brainstem auditory evoked potentials, lateral-spread responses, Z-L responses, facial corticobulbar motor evoked potentials, and blink reflexes. These methods have been applied to detect neuronal damage, to optimize the successful decompression of a facial nerve, to predict clinical outcomes, and to identify changes in the excitability of a facial nerve and its nucleus during MVD. This has resulted in multiple studies continuously investigating the clinical application of ION during MVD in patients with HFS. In this study we aimed to review the specific advances in methodologies and clinical research related to ION techniques used in MVD surgery for HFS over the last decade. These advances have enabled clinicians to improve the efficacy and surgical outcomes of MVD, and they provide deeper insight into the pathophysiology of the disease.

Usefulness of intraoperative monitoring in microvascular decompression for hemifacial spasm: a systematic review and meta-analysis

OBJECTIVE

To review the diagnostic accuracy and possible added value of Brainstem Auditory Evoked Potentials (BAEP) monitoring and Lateral Spread Response (LSR) monitoring in microvascular decompression surgery for hemifacial spasms.

METHODS

For this systematic review we followed the PRISMA guidelines. We searched different databases and bibliographies of articles. We included studies on BAEP and LSR monitoring that reported data on hearing outcome or efficacy. Selected studies were assessed for bias using the MINORS tool.

RESULTS

64 articles were selected for qualitative synthesis, 42 met inclusion criteria for meta-analysis. The overall incidence of hearing loss was 3.4%. For BAEP monitoring AUC and pooled OR with 95% confidence interval were 0.911 (0.753-0.933) and 7.99 (3.85-16.60) respectively. Short-term data on LSR monitoring showed an overall spasm relief rate of 89% with pooled OR, sensitivity and specificity with a 95% confidence interval of 8.80 (4.82-16.08), 0.911 (0.863-0.943) and 0.451 (0.342-0.564) respectively. Long-term data on LSR monitoring showed an overall spasm relief rate of 95% with pooled OR, sensitivity and specificity with a 95% confidence interval of 4.06 (2.15-7.64), 0.871 (0.817-0.911) and 0.39 (0.294-0.495) respectively.

CONCLUSION

The alarm criteria, a wave V latency prolongation of 1ms or a wave V amplitude decrement of 50%, proposed by the 'American Clinical Neurophysiology Society' are a sensitive predictor for postoperative hearing loss. Other BAEP wave changes, for example, complete loss of wave V, are more specific but correspond to irreversible damage and are therefore not useful as warning criteria. LSR monitoring has high diagnostic accuracy at short-term follow-up. At long-term follow-up, diagnostic accuracy decreases because most patients get spasm relief regardless of their LSR status. LSR persistence after surgery has a good long-term outcome, as long as an extensive exploration of the facial nerve has been performed.

Lateral spread response of different facial muscles during microvascular decompression in hemifacial spasm

OBJECTIVE

Interpreting lateral spread response (LSR) during microvascular decompression (MVD) for hemifacial spasm (HFS) is difficult when LSRs observed in different muscles do not match. We aimed to analyze LSR patterns recorded in both the orbicularis oris (oris) and mentalis muscles and their relationships with clinical outcomes.

METHODS

The data of 1288 HFS patients who underwent MVD between 2015 and 2018 were retrospectively reviewed. LSR was recorded in the oris and mentalis muscles through centrifugal stimulation of the temporal branch of the facial nerve after preoperative mapping. The disappearance of LSR following surgery, clinical outcomes, and the characteristics of LSR in oris were analyzed.

RESULTS

After surgery, LSR remained in 100 (7.7%) and 279 (21.6%) of the mentalis and oris muscles, respectively. The postoperative outcome correlated with LSR disappearance in the mentalis, not with that in the oris.

CONCLUSION

LSR patterns differed in each muscle and may not be correlated with clinical outcomes. LSR in the mentalis and oris muscles should be interpreted differently.

SIGNIFICANCE

We describe a monitoring protocol characterized by preoperative facial nerve mapping, antidromic stimulation, and recording from multiple muscles. We analyze differences in LSRs in the mentalis and oris muscles and suggest technical points for interpretation.

Predicting outcome of hemifacial spasm after microvascular decompression with intraoperative monitoring: A systematic review

BACKGROUND

Microvascular decompression has been established as a primary treatment for hemifacial spasm. Intraoperative monitoring is used during the surgery to guide neurosurgeons to determine whether the decompression of facial nerve from the vessel is sufficient. We performed a systematic review to assess the role of lateral spread response (LSR) monitoring in predicting hemifacial spasm outcomes after microvascular decompression.

METHOD

A systematic search of PubMed, ScienceDirect, Cochrane, and Google Scholar was conducted. We included studies that performed microvascular decompression surgery with intraoperative monitoring analyzing the correlation between lateral spread response and spasm relief. A critical appraisal was conducted for selected studies.

RESULT

Twenty-two studies comprising 6404 cases of hemifacial spasm, which underwent microvascular decompression surgery with intraoperative monitoring, were included. Of 15 articles that assessed symptoms shortly after surgery, 12 studies showed a significant correlation between lateral spread response resolution and disappearance of spasm. Four of six studies that evaluated the outcome at 3-month follow-up showed significant relationship between LSR and outcome, so did five of six articles that assessed spasm relief at 6-month follow-up. As much as 62.5% of studies (10 of 16) showed the result at long-term follow-up (≥1-year) was not significant.

CONCLUSION

Intraoperative monitoring during microvascular decompression surgery can be a useful tool to predict hemifacial spasm resolution. Though long-term outcomes of patients with LSR relief and persistence are similar, resolution of symptoms shortly after surgery will provide comfort to patients thereby improving their quality of life.

Spasm Freedom Following Microvascular Decompression for Hemifacial Spasm: Systematic Review and Meta-Analysis

BACKGROUND

Hemifacial spasm (HFS) is a debilitating disorder characterized by intermittent involuntary movement of muscles innervated by the facial nerve. HFS is caused by neurovascular compression along the facial nerve root exit zone and can be treated by microvascular decompression (MVD). The goal was to determine rates and predictors of spasm freedom after MVD for HFS.

METHODS

A literature search using the key terms "microvascular decompression" and "hemifacial spasm" was performed. The primary outcome variable was spasm freedom at last follow-up. Analysis was completed to evaluate for variables associated with spasm-free outcome.

RESULTS

A total of 39 studies including 6249 patients were analyzed. Overall spasm freedom rate was 90.5% (5652/6249) at a follow-up of 1.25 ± 0.04 years. There was no significant relationship between spasm freedom versus persistent spasm and age at surgery, timing of follow-up, gender, disease duration, side of disease, or vessel type. Spasm freedom was more likely after an initial surgery versus a redo MVD (odds ratio 4.16, 95% confidence interval 1.99-8.68; P < 0.01).

CONCLUSIONS

MVD works well for HFS with cure rates >90% at 1-year follow-up in 6249 patients from 39 studies. A significant predictor of long-term spasm freedom at 1 year was an initial MVD as compared to repeat MVD. The majority of published manuscripts on MVD for HFS are heterogeneous single-institutional retrospective studies. As such, a large-scale meta-analysis reporting outcome rates and evaluating significant predictors of spasm freedom provides utility in the absence of randomized controlled studies.

Prognostic Value of Abnormal Muscle Response During Microvascular Decompression for Hemifacial Spasm: A Meta-Analysis

OBJECTIVE

To perform a comprehensive meta-analysis to systematically assess the value of abnormal muscle response (AMR) in predicting the surgical outcome of patients with hemifacial spasm.

METHODS

The electronic database PubMed, Embase, Web of Science, and ScienceDirect were searched, and relevant articles were identified up to September 30, 2019. These data were extracted for pooled analysis, heterogeneity testing, sensitivity analysis, publication bias analysis, and Fagan plot analysis.

RESULTS

The disappearance of AMR during microvascular decompression was associated with a favorable short-term surgical outcome (pooled relative risk [RR], 1.42; 95% confidence interval [CI], 1.24-1.62; pooled RR adjusted for publication bias, 1.30; 95% CI, 1.08-1.57). The corresponding pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio were 0.91 (95% CI, 0.88-0.94), 0.34 (95% CI, 0.27-0.42), 1.4 (95% CI, 1.2-1.6), 0.26 (95% CI, 0.17-0.38), and 5 (95% CI, 3-9), respectively. The disappearance of AMR was almost ineffective in predicting the long-term surgical outcome (pooled RR, 1.09; 95% CI, 1.02-1.17; pooled RR adjusted for publication bias, 1.001; 95% CI, 0.92-1.09). The corresponding pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio were 0.90 (95% CI, 0.85-0.93), 0.28 (95% CI, 0.20-0.37), 1.2 (95% CI, 1.1-1.4), 0.38 (95% CI, 0.22-0.63), and 3 (95% CI, 2-6), respectively.

CONCLUSIONS

The disappearance of AMR during microvascular decompression demonstrates limited prognostic value for a favorable short-term outcome, and does not appear effective in predicting the long-term outcome of patients with hemifacial spasm.

An Intraoperative Multibranch Abnormal Muscle Response Monitoring Method During Microvascular Decompression for Hemifacial Spasm

BACKGROUND

Intraoperative abnormal muscle response (AMR) is widely used as an indicator during microvascular decompression surgery for hemifacial spasm. Usually only 1 muscle is recorded, and not all patients show a response, leaving the surgery somewhat blinded. We propose an improved method to record from multiple muscles innervated by multiple branches of the facial nerve to increase the positive AMR detection rate.

METHODS

Retrospective analysis was performed of 1604 patients with hemifacial spasm undergoing microvascular decompression at a single center. All patients were monitored for AMR by stimulating the zygomatic branch of the facial nerve. Only mentalis was recorded in 158 cases (single-branch AMR). Orbicularis oris, frontalis, and mentalis were simultaneously monitored in 148 cases (3-branch AMR), and platysma was further added in the remaining 1298 cases (4-branch AMR). Positive AMR detection rates were compared across the groups.

RESULTS

Total positive AMR detection rates significantly increased as more muscles were included in monitoring and were 74.1% for single-branch AMR, 86.5% for 3-branch AMR, and 98.4% for 4-branch AMR. Detection rates from single muscles were not significantly different across the groups. For all available cases, rates were 73.5% from mentalis, 47.2% from frontalis, 64.1% from orbicularis oris, and 40.8% from platysma.

CONCLUSIONS

This new multibranch AMR monitoring method can effectively increase the positive detection rate to as high as 98.4%. It is expected to better assist surgery.

Intraoperative Neurophysiological Monitoring during Microvascular Decompression Surgery for Hemifacial Spasm

Hemifacial spasm (HFS) is due to the vascular compression of the facial nerve at its root exit zone (REZ). Microvascular decompression (MVD) of the facial nerve near the REZ is an effective treatment for HFS. In MVD for HFS, intraoperative neurophysiological monitoring (INM) has two purposes. The first purpose is to prevent injury to neural structures such as the vestibulocochlear nerve and facial nerve during MVD surgery, which is possible through INM of brainstem auditory evoked potential and facial nerve electromyography (EMG). The second purpose is the unique feature of MVD for HFS, which is to assess and optimize the effectiveness of the vascular decompression. The purpose is achieved mainly through monitoring of abnormal facial nerve EMG that is called as lateral spread response (LSR) and is also partially possible through Z-L response, facial F-wave, and facial motor evoked potentials. Based on the information regarding INM mentioned above, MVD for HFS can be considered as a more safe and effective treatment.

Hemifacial Spasm Caused by Vascular Compression in the Cisternal Portion of the Facial Nerve: Report of Two Cases with Review of the Literature

Although primary hemifacial spasm (HFS) is mostly related to a vascular compression of the facial nerve at its root exit zone (REZ), its occurrence in association with distal, cisternal portion has been repeatedly reported during the last two decades. We report two patients with typical HFS caused by distal neurovascular compression, in which the spasm was successfully treated with microvascular decompression (MVD). Vascular compression of distal, cisternal portion of the facial nerve was identified preoperatively in the magnetic resonance imaging (MRI). It was confirmed again with intraoperative findings of compression of cisternal portion of the facial nerve by the meatal loop of the anterior inferior cerebellar artery (AICA) and absence of any offending vessel in the REZ of the facial nerve. Immediate disappearance of lateral spread response (LSR) after decompression and resolution of spasm after the operation again validated that HFS in the current patients originated from the vascular compression of distal, cisternal portion of the facial nerves. According to our literature review of 64 patients with HFS caused by distal neurovascular compression, distal compression can be classified by pure distal neurovascular compression (31 cases, 48.4%) and double compression (both distal segment and the REZ of the facial nerves, 33 cases [51.6%]) according to the presence or absence of simultaneous offender in the REZ. Eighty-four percent of 64 identified distal offenders were the AICA, especially its meatal and postmeatal segments. Before awareness of distal neurovascular compression causing HFS and sophisticated MRI imaging (before 2000), the rate of reoperation was high (58%). Preoperative MRI and intraoperative monitoring of LSR seems to be an essential element in determination of real offending vessel in MVD caused by distal offender.

Long-term surgical results in microvascular decompression for hemifacial spasm: efficacy, morbidity and quality of life

Hemifacial spasm is a condition that may severely reduce patients' quality of life. Microvascular decompression is the neurosurgical treatment of choice. The objective of this work was to describe the efficacy and morbidity of microvascular decompression for hemifacial spasm, evaluate the long-term efficacy on the quality of life and investigate prognostic factors for failure of the procedure. A retrospective study of 446 cases of hemifacial spasm treated by 511 retrosigmoid microvascular decompression over 22 years was conducted. Epidemiological, clinical and imaging findings, treatment modalities and outcomes of patients with pre- and postoperative HSF-8 quality of life questionnaire were studied. Success rate was 82% after first surgery and 91.6% after revision surgery. A low rate of perioperative morbidity was found. Facial palsy was mostly transient (5.5% transient and 0.2% permanent) and cochleovestibular deficit was seen in 4.8% of patients. Revision surgery increased nervous lesions (10.6% to 20.7%). Mean quality of life scores were significantly improved from 18 to 2 over 32, evaluated 7.3 years after surgery. Predictive factors of surgical failure were single conflicts (p = 0.041), atypical vasculo-nervous conflicts involving other vessel than postero-inferior cerebellar artery (p = 0.036), such as vein (p = 0.045), and other compression sites than root exit zone (p = 0.027). Retrosigmoid microvascular decompression is a safe and effective treatment of hemifacial spasm. Revision surgery is not to be excluded in case of failure, but does place patients at risk for more complications. Quality of life is improved in the long-term, indicating objective and subjective satisfaction.

An investigation into quality of life improvement in patients undergoing microvascular decompression for hemifacial spasm

OBJECTIVE Hemifacial spasm (HFS) is a movement disorder characterized by involuntary spasms of the facial muscles, and it can negatively impact quality of life (QOL). This retrospective study and systematic review with meta-analysis was conducted to investigate the QOL in patients with HFS following intervention with microvascular decompression (MVD) and botulinum toxin (BT). METHODS In the retrospective analysis, a QOL questionnaire was administered to all patients undergoing MVD performed by a single surgeon. The QOL questionnaire included unique questions developed based on the authors' experience with HFS patients in addition to the health-related QOL HFS-8 questionnaire. The authors also report on a systematic review of the English literature providing outcomes and complications in patients with HFS undergoing treatment with either MVD or BT. RESULTS Regarding the retrospective analysis, 242 of 331 patients completed the questionnaire. The mean score of the 10 QOL questions improved from 22.78 (SD 9.83) to 2.17 (SD 5.75) following MVD (p < 0.001). There was significant improvement across all subscales of the questionnaire between pre- and postoperative responses (p < 0.001). Regarding the systematic review, it is reported that approximately 90% of patients undergoing MVD for HFS experience a complete recovery from symptoms, whereas the mean peak improvement of symptoms following treatment with BT is 77%. Furthermore, patients undergoing MVD reported a greater improvement in the mean supplemental index of QOL as compared with patients receiving BT therapy. CONCLUSIONS Microvascular decompression offers a significant improvement in QOL in well-selected patients suffering from HFS, and may offer an increased benefit for QOL over BT injections.

Facial spasms, but not hemifacial spasm: a case report and review of literature

INTRODUCTION

Facial spasms represent a complicated array of neurological motor disorders with unique diagnostic and treatment algorithms. Due to the rarity of many of these disorders in the pediatric population, special care must be taken in identifying subtle differences in presentation of these disorders.

METHODS

We present a case of a 3-year-old boy diagnosed with a brainstem ganglioglioma, Chiari 1 malformation, and a 2-year history of left-sided facial spasms. Stereotyped facial contractions and subtle eye deviation occurred every 10 s, with downward movement rather than upward elevation of the eyebrow.

RESULTS

MRI revealed absence of a clear compressive vessel of the centrally-myelinized portion of the facial nerve, and EMG of the left facial nerve demonstrated no abnormal motor response or evidence of "lateral spread." Given these findings, a diagnosis of hemifacial seizures was made. Microvascular decompression was not recommended, and botulinum toxin injection was not pursued; however, the patient has remained refractory to antiepileptic drugs, possibly due to biochemical alteration by his ganglioglioma. He may eventually require surgical debulking should his symptoms progress.

CONCLUSION

Hemifacial spasm is a well-recognized disorder, but similar conditions can, at times, imitate its appearance. While our patient presented with facial spasms, his clinical history, examination, and radiographic and electrophysiological findings were more consistent with hemifacial seizures secondary to a brainstem lesion, rather than hemifacial spasms. It is important to distinguish the two entities, as misdiagnosis and inappropriate diagnostic or therapeutic measures may be taken inadvertently.