The Current Status of Microvascular Decompression for the Treatment of Hemifacial Spasm in Japan: An Analysis of 2907 Patients Using the Japanese Diagnosis Procedure Combination Database

Comparison of Surgical Outcomes in Microscopic and Fully Endoscopic Microvascular Decompression for Hemifacial Spasm

Fully endoscopic microvascular decompression is increasingly being used to treat hemifacial spasm; however, its efficacy must be validated by comparing it with conventional microscopic microvascular decompression. In this study, we aimed to compare the surgical outcomes of microsurgical and endoscopic microvascular decompression for hemifacial spasm and discuss the usefulness and risks of endoscopic treatment. A total of 40 patients with hemifacial spasm were retrospectively evaluated at a single institution between 2016 and 2022, including 33 patients who underwent microscopic microvascular decompression (microvascular decompression group) and 7 patients who underwent fully endoscopic microvascular decompression group, which was chosen for patients with sufficient space in the cerebellopontine cistern for endoscopic manipulation. Statistical analyses of the microvascular decompression group and the endoscopic microvascular decompression group were performed to compare patient background and surgical outcomes. No significant differences in age, sex, or affected side were observed between the 2 groups. At the 6-month follow-up, substantial improvement was observed in more than 85% of the patients in each group. Delayed facial palsy and mild lower cranial nerve palsy, such as hoarseness, were more common in the endoscopic microvascular decompression group than in the microvascular decompression group, although there were no significant differences in the rate of complications between the 2 groups. All complications were alleviated within 3 months after surgery. During endoscopic microvascular decompression, interference between the endoscope and instruments can cause neural damage owing to the limited space along the petrosal surface of the cerebellum. Our results suggest that endoscopic procedures cannot always be used as a substitute for conventional microscopic microvascular decompression.

Correlation between Delayed Relief after Microvascular Decompression and Morphology of the Lateral Spread Response in Patients with Hemifacial Spasm-Temporal versus Mandibular Branch Stimulation

Although microvascular decompression (MVD) is a reliable treatment for hemifacial spasm (HFS), delayed postoperative relief is one of its main issues. We previously evaluated the morphology of the lateral spread response (LSR) and reported the correlation between delayed relief after MVD and polyphasic morphology of the LSR. The purpose of this study was to investigate the correlation between the morphology of the LSR with stimulation of the temporal and mandibular branches of the facial nerve and delayed relief of persistent HFS after MVD. We retrospectively analysed and compared data from 49 of 205 consecutive patients who underwent MVD for HFS at our hospital between January 2015 and March 2022. Based on the pattern of the initial LSR morphology, patients were divided into 4 groups (LSR with temporal branch stimulation/LSR with mandibular branch stimulation; polyphasic/polyphasic group, polyphasic/monophasic group, monophasic/polyphasic group, monophasic/monophasic group). The results of MVD surgery for HFS were evaluated 1 week, 1 month and 1 year postoperatively, by evaluating whether or not the symptoms of HFS persisted at the time of each follow-up. We found significant differences in residual postoperative HFS 1 week postoperatively among the 4 groups (p < 0.05), as assessed using m*n Yates chi-square test. There is a significant correlation between delayed relief after MVD and polyphasic morphology of the initial LSR in patients with HFS. The LSR with temporal rather than mandibular branch stimulation might be useful for predicting delayed relief following MVD in HFS patients.

Correlation between Delayed Relief after Microvascular Decompression and Morphology of the Lateral Spread Response in Patients with Hemifacial Spasm-Further Examination with Compound Motor Action Potentials

Although microvascular decompression (MVD) is a reliable treatment for hemifacial spasm (HFS), postoperative delayed relief is one of its main issues. We previously evaluated the morphology of the lateral spread response (LSR) and reported correlation between delayed relief after MVD and polyphasic morphology of the LSR. This study aimed to investigate the morphology of LSR and the course of recovery of the compound motor action potential (CMAP), to better understand the pathophysiology of delayed healing of HFS. Based on the pattern of the initial LSR morphology on temporal and marginal mandibular branches stimulation, patients were divided into two groups: the monophasic and polyphasic groups. The results of MVD surgery and sequential changes in the CMAP were evaluated 1 week, 1 month, 1 year, and final follow-up after the surgery. Significantly higher rates of persistent postoperative HFS were observed in patients with the polyphasic type of initial LSR at 1 week and 1 month after the surgery (P < 0.05, respectively). In the polyphasic group, the amplitude of the CMAP tended to gradually improve with time, while in the monophasic group, the amplitude of the CMAP decreased on the seventh postoperative day, followed by its gradual improvement. There is a significant correlation between delayed relief after MVD and polyphasic morphology of the initial LSR in patients with HFS. In the polyphasic group, CMAP recovered earlier and showed less reduction in amplitude, suggesting segmental demyelination, with less damage to peripheral nerves.

Significant Correlation between Delayed Relief after Microvascular Decompression and Morphology of the Abnormal Muscle Response in Patients with Hemifacial Spasm

Although microvascular decompression (MVD) is a reliable treatment for hemifacial spasm (HFS), postoperative delayed relief of persistent HFS is one of the main issues. In patients with hemifacial spasm, stimulation of a branch of the affected facial nerve elicits an abnormal response in the muscles innervated by another branch. Several specific types of waves were found in the abnormal muscle response (AMR). This study aimed to confirm the relationship between the initial morphology of the AMR wave and delayed relief of persistent HFS after MVD. We retrospectively analyzed and compared the data from 47 of 155 consecutive patients who underwent MVD for HFS at our hospital between January 2015 and March 2020. Based on the pattern of the initial AMR morphology on orbicularis oculi and mentalis muscle stimulation, patients were divided into two groups, namely, the monophasic and polyphasic groups. The results of MVD surgery for HFS were evaluated 1 week, 1 month, and 1 year postoperatively, by evaluating whether or not the symptoms of HFS persisted at the time of each follow-up. There were significantly higher rates of persistent postoperative HFS in patients with the polyphasic type of initial AMR at 1 week and 1 month after the surgery (p < 0.05, respectively), as assessed using Yates chi-squared test and Fisher's exact test. A significant correlation was observed between delayed relief after MVD and polyphasic morphology of the AMR in electromyographic analysis in patients with hemifacial spasm.

A multivariable prediction model for recovery patterns and time course of symptoms improvement in hemifacial spasm following microvascular decompression

BACKGROUND

Microvascular decompression (MVD) success rates exceed 90% in hemifacial spasm (HFS). However, postoperative recovery patterns and durations are variable.

OBJECTIVE

We aim to study factors that might influence the postoperative patterns and duration needed until final recovery.

METHOD

Only patients following de-novo MVD with a minimum follow-up of 6 months were included. Overall trend of recovery was modeled. Patients were grouped according to recognizable clinical recovery patterns. Uni- and multivariable analyses were used to identify the factors affecting allocation to the identified patterns and time needed to final recovery.

RESULTS

A total of 323 (92.6%) patients had > 90% symptom improvement, and 269 (77.1%) patients had complete resolution at the last follow-up. The overall trend of recovery showed steep remission within the first 6 months, followed by relapse peaking around 8 months with a second remission ~ 16 months. Five main recovery patterns were identified. Pattern analysis showed that evident proximal indentation of the facial nerve at root exit zone (REZ), males and facial palsy are associated with earlier recovery at multivariable and univariable levels. anterior inferior cerebellar artery (AICA), AICA/vertebral artery compressions and shorter disease durations are related to immediate resolution of the symptoms only on the univariable level. Time analysis showed that proximal indentation (vs. distal indentation), males and facial palsy witnessed significantly earlier recoveries.

CONCLUSION

Our main finding is that in contrast to peripheral indentation, proximal indentation of the facial nerve at REZ is associated with earlier recovery. Postoperative facial palsy and AICA compressions are associated with earlier recoveries. We recommend a minimum of 1 year before evaluating the final outcome of MVD for HFS.

Sequential Change of Facial Nerve Motor Function after Microvascular Decompression for Hemifacial Spasm: An Electrophysiological Study

Hemifacial spasm (HFS) patients occasionally present with preoperative facial weakness (PFW) or develop delayed facial palsy (DFP) after microvascular decompression (MVD). This study is aimed to evaluate the neurophysiology underlying facial nerve motor dysfunction in HFS patients preoperatively and postoperatively. In all, 54 HFS patients without prior botulinum toxin injection who underwent MVD were retrospectively reviewed. The compound muscle action potential (CMAP) amplitude ratios of the affected and unaffected facial nerves, measured at 4 time points from preoperation to 1 year post-surgery, were aggregated. Clinical outcomes and the CMAP amplitude ratios were evaluated. Six patients (11.1%) presented with PFW, which correlated with advanced age (p = 0.007) and symptom duration (p = 0.001). The average duration to achieve PFW relief was 2.67 months postoperatively. The preoperative CMAP amplitude ratios of PFW patients were lower than those of patients without PFW (85.3% vs 95.7%). The ratios showed the lowest value at 1-week post-surgery in both groups (70.3% vs 90.9%), had a tendency toward improvement at 1 month, and finally recovered to almost the same level as that before the surgery at 1 year. Three patients (5.6%), whose CMAP ratios showed a persistent decrease from 1 week (56.5%) to 1 month (31%) after MVD, developed DFP. This study illustrates PFW in HFS patients reflects facial nerve axonal stress. MVD is effective in resolving spasm and PFW, without long-term damage to the facial nerve in most patients. In DFP patients, the direct and subsequent secondary axonal disorder develops on the postoperative facial nerve.

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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Nerve Compression Syndromes in the Posterior Cranial Fossa

BACKGROUND

Nerve compression syndromes in the posterior cranial fossa can severely impair patients' quality of life. There is often uncertainty about the best treatment. In this article, we provide an overview of these conditions and the corresponding treatment strategies.

METHODS

This review is based on pertinent publications retrieved by a selective search in PubMed and on a scientific analysis of the authors' patient collective.

RESULTS

These syndromes are caused by compression of a cranial nerve by an artery or vein at the zone of the nerve's entry to or exit from the brainstem. The best-known neurovascular compression syndrome is trigeminal neuralgia, followed by hemifacial spasm. Less well known are glossopharyngeal neuralgia, nervus intermedius neuralgia, and vestibular paroxysmia. The initial treatment of trigeminal neuralgia is medical: the first line of treatment is with sodium-blocking anticon- vulsants, such as carbamazepine. For patients with hemifacial spasm, botulinum toxin injection is the recommended initial treatment and often leads to a satisfactory regression of the spasms. If these treatments fail, a microvascular decompression operation is indicated. The aim of the procedure is to separate the irritating vessel from the nerve and to keep these structures apart permanently. There is hardly any available evidence on these treatment strategies from randomized controlled trials.

CONCLUSION

Nerve compression syndromes in the posterior cranial fossa can generally be treated nonsurgically at first. Over the course of the condition, however, treatment failure or intolerable side effects may arise. In such cases, a microvascu- lar decompression operation is indicated. This is a causally directed form of treat- ment that generally yields very good results.

The Current Status of Microvascular Decompression for the Treatment of Trigeminal Neuralgia in Japan: An Analysis of 1619 Patients Using the Japanese Diagnosis Procedure Combination Database

Microvascular decompression (MVD) is a widely used, safe, and effective treatment for trigeminal neuralgia (TGN). However, the extent of application of this therapeutic method and its outcomes in Japan are currently unclear. To address these questions, the authors analyzed the use of MVD for the treatment of TGN during the 33-month period from July 2010 to March 2013, using data contained in the Diagnosis Procedure Combination database. The analysis revealed that MVD was used for the treatment of TGN in 1619 cases (608 men, 1011 women), with approximately 1.66 times more women treated than men. MVD for TGN was most frequently performed in individuals 60 to 79 years of age; of particular note was the remarkable increase in the number of women in this particular category. The overall number of procedures performed per 100,000 population/year in Japan was 0.46. The number of procedures was larger in prefectures with higher populations, with a tendency toward a higher number of MVD procedures performed in the area designated West than in the East. Discharge outcomes indicated that cure and improvement were achieved in 97.6% of cases, with a mortality rate of 0.2%, and no differences in discharge outcomes between men and women. The mean length of hospital stay in patients undergoing MVD for TGN was 14.8 days. This analysis revealed discernable trends in the use of MVD for the treatment of TGN in Japan.