The cranial nerve vascular compression syndrome: II. A review of pathophysiology

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.

Operative Findings of over 5000 Microvascular Decompression Surgeries for Hemifacial Spasm: Our Perspective and Current Updates

Hemifacial spasm (HFS) is a hyperactive cranial neuropathy, and it has been well established that the cause of primary HFS is compression on the root exit zone (REZ) of the facial-vestibulocochlear nerve complex (CN VII-VIII) by a vessel or vessels. MVD is the only curative treatment option for HFS with a high success rate and low incidence of recurrence and complications. We categorize six classical compressive patterns on the REZ as well as five challenging types. Knowledge of these patterns may help in achieving a better surgical outcome.

Brain White Matter Structural Alteration in Hemifacial Spasm: A Diffusion Tensor Imaging Study

OBJECTIVE

To analyze the changes in the white matter structure of the whole brain in hemifacial spasm (HFS) patients by using the tract-based spatial statistics (TBSS) method.

MATERIALS AND METHODS

29 HFS patients without anxiety and depression and 29 healthy controls with matching age, sex, and education were selected. All subjects received a 3.0T magnetic resonance (MR) brain diffusion tensor imaging scan. Tract-based spatial statistics method was used to analyze the changes in white matter structure in the whole brain and obtained the cerebral white matter fibrous areas exhibiting significant intergroup differences. The fractional anisotropy (FA), mean diffusivity, axial diffusivity, and radial diffusivity of these areas were abstracted. Analyzed the correlation between these diffusion metrics and clinical variables (disease duration, spasm severity).

RESULTS

Compared with the healthy controls group, the HFS group exhibited significantly lower FA in the forceps minor, bilateral anterior thalamic radiation, and right superior longitudinal fasciculus ( P <0.05, threshold-free cluster enhancement corrected). Cohen grading scale of HFS patients was negatively correlated with FA of forceps minor.

CONCLUSION

Based on TBSS analysis, the injury of white matter fiber tracts in HFS patients was found, including forceps minor, bilateral anterior thalamic radiation, and right superior longitudinal fasciculus. The changes of FA values in forceps minor were negatively correlated with the Cohen grading scale, suggesting that the alteration of white matter fiber in the genu-of-corpus-callosum-cortex circuit plays an important role in the neuro-pathological mechanism of HFS. Combined with previous research, it is also necessary to further explore the change of the superior longitudinal fasciculus in the future.

Reoperation for residual or recurrent hemifacial spasm after microvascular decompression

PURPOSE

Microvascular decompression (MVD) surgery is the only potential curative method for hemifacial spasm (HFS). Little attention is paid to those recurrent/residual HFS cases. We want to study the potential etiology of those recurrent/residual HFS cases and evaluate the value of reoperation.

METHODS

We retrospectively reviewed reoperation hemifacial spasm patients in our hospital. Intraoperative videos or images were carefully reviewed, and the etiology of recurrent/residual HFS is roughly divided into three categories. Intraoperative findings, surgical outcomes, and complications were carefully studied to assess the value of reoperation for recurrent/residual HFS patients.

RESULTS

A total of 28 cases were included in our case series. Twenty-three of them are recurrent HFS cases, and 5 of them are residual HFS cases. The mean follow-up duration is 24.96 months. There are seventeen patients with missed culprit vessels or insufficient decompression of root exit zone (REZ), eight patients with Teflon adhesion, and three patients with improper application of decompression materials in our case series. The final reoperation outcome with 17 excellent, seven good, and four fair, respectively. Eight (28.57%) of them experienced long-term complications after reoperation.

CONCLUSION

Re-operation for recurrent/residual HFS is an effective therapy and can achieve a higher cure rate. However, the complication rate is higher compared to the first MVD surgery. Accurately identifying REZ and proper decompression strategies to deal with the culprit vessels are very important for surgical success.

TRIAL REGISTRATION NUMBER

UIN: researchregistry7603. Date of registration: Jan. 31st, 2022 "retrospectively registered".

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.

Prognostic factors for long-term outcomes of microvascular decompression in the treatment of glossopharyngeal neuralgia: a retrospective analysis of 97 patients

OBJECTIVE

The authors aimed to investigate predictors of postoperative outcomes of microvascular decompression (MVD) for the treatment of glossopharyngeal neuralgia (GPN).

METHODS

A cohort of 97 patients with medically refractory GPN who underwent MVD at the authors' institution between January 2010 and July 2019 was retrospectively reviewed. Univariate and multivariate regression models were used to identify predictors of long-term outcome in patients after MVD.

RESULTS

Eighty-nine patients (91.8%) reported immediate and complete relief of pain after the procedure. Of the remaining 8 patients (8.2%), 6 achieved partial pain relief and pain gradually diminished within 2 weeks after surgery, and 2 did not experience postoperative pain relief. In univariate Cox regression analysis, venous compression of the glossopharyngeal nerve root entry zone (HR 3.591, 95% CI 1.660-7.767, p = 0.001) and lower degree of neurovascular conflict (HR 2.449, 95% CI 1.177-5.096, p = 0.017) were significantly associated with worse pain-free survival. In multivariate Cox regression analysis, venous compression (HR 8.192, 95% CI 2.960-22.669, p < 0.001) and lower degree of neurovascular conflict (HR 5.450, 95% CI 2.069-14.356, p = 0.001) remained independently associated with worse pain-free survival.

CONCLUSIONS

Venous compression of the glossopharyngeal nerve root entry zone and lower degree of neurovascular conflict were significantly correlated with shorter pain-free survival in patients who underwent MVD for GPN. Microvascular decompression is a safe, feasible, and durable approach with a low complication rate for the treatment of GPN.

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

BACKGROUND

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.

OBJECTIVE

To analyze the LSR 1 month postoperatively and to evaluate its prognostic value until 1 year postsurgery.

METHODS

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.

RESULTS

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%.

CONCLUSION

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.

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.

Microsurgery and Neuromodulation for Facial Spasms

Facial spasms are of various types. Hemifacial spasm (HFS) is characterized by unilateral tonic-clonic contractions of facial muscles, following a specific pattern of disease progression. It has well-delineated clinical, radiological and electrophysiological features. We have conducted an extensive review of existing literature on the subject, as regards etiopathogenesis, clinical features, investigations and management options for facial spasms. Primary Hemifacial spasm (HFS) may be treated using pharmacotherapy, botulinum toxin injections or microvascular decompression surgery. Microvascular decompression has the potential to reverse the pathological changes of the disease and has proved to be the most successful of all treatment options. Other facial spasms are exceedingly difficult to treat and may need neuromodulation as an option. The following article attempts to review the clinical features and therapeutic approaches to managing patients with facial spasms.

Abnormal Regional Spontaneous Brain Activity and Its Indirect Effect on Spasm Ratings in Patients With Hemifacial Spasm

PURPOSE

Three classical methods of resting-state functional magnetic resonance imaging (rs-fMRI) were employed to explore the local functional abnormalities and their effect on spasm ratings in hemifacial spasm (HFS) patients.

METHODS

Thirty HFS patients and 30 matched healthy controls (HCs) were recruited. Rs-fMRI data, neurovascular compression (NVC) degree and spasm severity were collected in each subject. Fractional amplitude of low-frequency fluctuation (fALFF), regional homogeneity (ReHo), and degree centrality (DC) were calculated in the whole brain voxels. Two sample t-tests were performed to investigate group differences of fALFF, ReHo, and DC. Correlation analysis was performed to assess the relationships between the regional brain abnormalities and clinical variables in HFS.

RESULTS

Compared with HCs, HFS patients exhibited increased fALFF in the left precuneus and right posterior cingulate cortex (PCC), together with increased ReHo in the bilateral PCC and bilateral precuneus. Decreased ReHo was observed in the right middle occipital gyrus (MOG), right superior occipital gyrus (SOG), right cuneus, and right angular gyrus (AG) in HFS patients. Moreover, ReHo in the right PCC were positively correlated with NVC degree and spasm severity in HFS patients, respectively. Mediation analysis revealed that increased ReHo in the right PCC regulated the neurovascular compression degree, and further resulted in increased spasm ratings.

CONCLUSION

Our study revealed regional brain dysfunctions from different perspectives and an indirect effect of ReHo in right PCC on spasm ratings predominantly through the alteration of NVC.

[Hemifacial spasm]

Hemifacial spasm (HFS), or facial hemispasm, is a paroxysmal hyperkinetic disorder involving muscles innervated by the facial nerve, mainly on the one hand. The development of HFS is based on neurovascular conflict. However, it is impossible to explain the clinical manifestations of HFS only by nerve compression. Both peripheral and central mechanisms are involved in the generation of HFS, with the formation of ephaptic transmission, antidromic excitation, primary or secondary hyper-excitability of the nuclear and supranuclear level of innervation. Two treatment methods are pathogenetically justified: microvascular decompression (MVD) and botulinum toxin (BTX) injections. The effectiveness of MVD is 95.37% with full or partial recovery. The recurrence rate does not exceed 2.4%. Facial nerve paralysis (2.7-22.5%) and hearing loss (1.9-20%) are the most common complications of treatment with the use of the MVD for HFS with partial or complete cure in most cases. Botulinum toxin injection chemo-denervation is a first-line treatment of primary and secondary HFS. HFS is an officially registered indication for the drug dysport (abobotulotoxin) (ABO) in the Russian Federation. Total doses of ABO ranged from 25 to 150 units for one side depending on the severity of the clinical manifestations. Studies demonstrate the statistically significant benefits of HFC treatment with ABO. ABO is generally well-tolerated. Adverse events (up to 3.6%) are transient and include ptosis, lacrimation, blurred vision, double vision, dry eyes and weak facial muscles.

Facial motor evoked potential with paired transcranial magnetic stimulation: prognostic value following microvascular decompression for hemifacial spasm

OBJECTIVE

Microvascular decompression (MVD) is widely considered the treatment of choice for hemifacial spasm (HFS), but not all patients immediately benefit from it. Numerous electrophysiological tests have been employed to monitor the integrity of the facial nerve prior to, during, and after MVD treatment. The authors sought to verify if facial motor evoked potential (FMEP) with paired transcranial magnetic stimulation (pTMS) can be utilized as a tool to predict prognosis following MVD for HFS.

METHODS

FMEP using pTMS was performed preoperatively and postoperatively for 527 HFS patients who underwent an MVD treatment. Various interstimuli intervals (ISIs), which included 2, 10, 20, 25, 30, 75, and 100 msec, were applied for each paired stimulation and pTMS(%) was obtained. A graph of pTMS(%) versus each ISI was drawn for every patient and its pattern was analyzed in accordance with patients' clinical outcomes.

RESULTS

With ISIs of 75 and 100 msec, pTMS(%) was physiologically further inhibited, whereas it was relatively facilitated under ISIs of 20, 25, and 30 msec; loss of this specific pattern, that is, further inhibition-relative facilitation, indicated impaired integrity of the facial nerve. Those patients who immediately benefited from an MVD and experienced no relapse tended to show proper restoration of this further inhibition-relative facilitation pattern (p = 0.01). Greater resemblance between the physiological pattern of pTMS(%) and postoperative pTMS(%) was correlated to better outcome (p = 0.019).

CONCLUSIONS

A simple linear graph of pTMS(%) versus each ISI may be a helpful tool to predict prognosis for HFS following an MVD.

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.

Reduced inhibition in brainstem circuits in classical trigeminal neuralgia

OBJECTIVE

We hypothesized that prepulse modulation (PPM) would be altered in trigeminal neuralgia (TN) if suprasegmental inhibitory network involvement was present and tested our hypothesis in a group of patients with classical TN.

METHODS

The study enrolled nine consecutive patients with classical TN and 14 healthy subjects. Diagnosis and classification followed the International Classification of Headache Disorders-third edition (beta version). The blink reflex (BR) and BR-PPM were recorded. Ipsilateral recordings were made after stimulating each trigeminal nerve in the patient group whereas right-sided recordings were performed after stimulating the right trigeminal nerve in the healthy subjects. A conditioning electrical stimulus was applied to the ipsilateral median nerve at interstimulus intervals (ISIs) of 50 and 100 ms before the test stimulus to the supraorbital nerve.

RESULTS

The unconditioned BR recordings were similar in all groups. In the healthy subjects, the prepulse stimulus resulted in a reduced R2 magnitude (p = 0.000, Friedman's test) and longer R2 latency (p = 0.008, Friedman's test) at ISIs of 50 and 100 ms in comparison with unconditioned recordings. The R2 latency differed significantly between the unconditioned recordings and the ISI of 100 ms. In the patients with TN, no significant change was observed on either the symptomatic or asymptomatic sides.

CONCLUSIONS

There is a bilateral prepulse inhibition deficit in TN, even on the asymptomatic side. Our findings provide electrophysiological evidence for suprasegmental changes and loss of filtering activity at the brainstem in level TN.

Delayed facial palsy after microvascular decompression for hemifacial spasm: friend or foe?

OBJECTIVE

The authors investigated the incidence, clinical course, and predisposing factors associated with delayed facial palsy (DFP) following microvascular decompression (MVD).

METHODS

The authors reviewed the records of 310 patients (311 cases) who were followed after MVD for hemifacial spasm (HFS). Of these patients, 45 (14.5%) developed DFP after MVD. The clinical characteristics and predisposing factors of the patients with HFS were investigated to identify prognostic factors that predicted the development of DFP after MVD. Log-rank tests were used to compare times to symptom disappearance, and a logistic regression analysis was performed to compare clinical characteristics between patients who developed DFP and those who did not.

RESULTS

HFS was completely resolved immediately after MVD in 158 cases (50.8%), and HFS eventually disappeared in 289 (92.9%) of the cases. Of the 45 patients with DFP, 17 were men and 28 were women. DFP occurred between postoperative Days 1 and 44 (mean 9.67 days). Finally, 44 patients (97.8%) completely recovered. The average time to recovery was 3.9 months (range 1–24 months). Patients who had experienced an immediate disappearance of HFS experienced a significantly higher occurrence of DFP than those who did not (odds ratio 0.383, 95% confidence interval 0.183–0.802; p = 0.011). In addition, preoperative botulinum neurotoxin injections negatively influenced the occurrence of DFP (p = 0.016).

CONCLUSIONS

In this study, the incidence rate of DFP was slightly higher than previously reported values. Moreover, DFP can occur even when spasms disappear immediately after MVD, but the patients with DFP can fully recover within weeks.

Tenth case of bilateral hemifacial spasm treated by microvascular decompression: Review of the pathophysiology

BACKGROUND

Bilateral hemifacial spasm (BHFS) is a rare neurological syndrome whose diagnosis depends on excluding other facial dyskinesias. We present a case of BHFS along with a literature review.

METHODS

A 64-year-old white, hypertense male reported involuntary left hemiface contractions in 2001 (aged 50). In 2007, right hemifacial symptoms appeared, without spasm remission during sleep. Botulinum toxin type A application produced partial temporary improvement. Left microvascular decompression (MVD) was performed in August 2013, followed by right MVD in May 2014, with excellent results. Follow-up in March 2016 showed complete cessation of spasms without medication.

RESULTS

The literature confirms nine BHFS cases bilaterally treated by MVD, a definitive surgical option with minimal complications. Regarding HFS pathophysiology, ectopic firing and ephaptic transmissions originate in the root exit zone (REZ) of the facial nerve, due to neurovascular compression (NVC), orthodromically stimulate facial muscles and antidromically stimulate the facial nerve nucleus; this hyperexcitation continuously stimulates the facial muscles. These activated muscles can trigger somatosensory afferent skin nerve impulses and neuromuscular spindles from the trigeminal nerve, which, after transiting the Gasser ganglion and trigeminal nucleus, reach the somatosensory medial posterior ventral nucleus of the contralateral thalamus as well as the somatosensory cortical area of the face. Once activated, this area can stimulate the motor and supplementary motor areas (extrapyramidal and basal ganglia system), activating the motoneurons of the facial nerve nucleus and peripherally stimulating the facial muscles.

CONCLUSIONS

We believe that bilateral MVD is the best approach in cases of BHFS.

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.

Prognostic ability of intraoperative electromyographic monitoring during microvascular decompression for hemifacial spasm to predict lateral spread response outcome

OBJECTIVE

Abnormal lateral spread response (LSR) is a typical finding in facial electromyography (EMG) in patients with hemifacial spasm (HFS). Although intraoperative monitoring of LSR has been widely used during microvascular decompression (MVD), the prognostic value of this monitoring is still debated. The purpose of this study was to determine whether such monitoring exhibits prognostic value for the alleviation of LSR after treatment of HFS.

METHODS

Between January 2009 and December 2013, a total of 582 patients underwent MVD for HFS with intraoperative EMG monitoring at Kyung Hee University Hospital. The patients were categorized into 1 of 2 groups according to the presence of LSR at the conclusion of surgery (Group A, LSR free; Group B, LSR persisting). Patients were assessed for the presence of HFS 1 day, 6 months, and 1 year after surgery. Various parameters, including age, sex, symptom duration, offending vertebral artery, and offending perforating artery, were evaluated for their influence on surgical and electrophysiological results.

RESULTS

Overall, HFS was alleviated in 455 (78.2%) patients 1 day after MVD, in 509 (87.5%) patients 6 months after MVD, and in 546 (93.8%) patients 1 year after MVD. Patients in Group B were significantly younger than those in Group A (p = 0.022). Patients with a symptom duration of less than 1 year were significantly more likely to be classified in Group A than were patients whose symptoms had persisted for longer than 10 years (p = 0.023); however, analysis of the entire range of symptom durations did not reveal a significant effect (p = 0.132). A comparison of Groups A and B according to follow-up period revealed that HFS recovery correlated with LSR alleviation over a shorter period, but the same was not true of longer periods; the proportions of spasm-free patients were 80.6% and 71.1% (p = 0.021), 89.4% and 81.9% (p = 0.022), and 93.5% and 94.6% (p = 0.699) 1 day, 6 months, and 1 year after surgery in Groups A and B, respectively.

CONCLUSIONS

Although intraoperative EMG monitoring during MVD was beneficial for identifying the offending vessel and suggesting the most appropriate surgical end point, loss of LSR did not always correlate with long-term HFS treatment outcome. Because the HFS cure rate improved over time, revision might be considered for persistent LSR when follow-up has been performed for more than 1 year and the spasm remains despite adequate decompression.

An optimized abnormal muscle response recording method for intraoperative monitoring of hemifacial spasm and its long-term prognostic value

BACKGROUND

Intraoperative electrophysiological monitoring is used to determine whether decompression is sufficient during microvascular decompression (MVD) for hemifacial spasm (HFS). However, the real offending vessel is sometimes neglected by the neurosurgeons. Here, we reported our experience in using optimized abnormal muscle response (AMR) monitoring and continuous intraoperative monitoring for MVD.

METHODS

This study included 2161 HFS patients who underwent MVD using traditional (1023 patients) and optimized (1138 patients) methods. Modified AMR monitoring was adopted in our study, with the zygomatic branch of the facial nerve stimulated and the temporal branch, buccal branch, marginal mandibular branch and cervical branch of the facial nerve detected for AMR. These cases were analyzed retrospectively with emphasis on the postoperative outcomes and intraoperative findings. The therapeutic effect was evaluated at day 1, month 3 and year 1 after operation.

RESULTS

The relief rate at day 1, month 3 and year 1 after operation for patients who employed optimized AMR recording method was 95.1%, 97.4% and 99.3%, comparing with 92.2%, 95.0% and 97.8% in traditional method. There was significant difference in achieved immediate remission and recovery rate during 12-month follow-up between the two groups (P < 0.05). The modified intraoperative monitoring showed the sensitivity of AMR disappearance to judge the relief at day 1, month 3 and year 1 after HFS operation was 95.7%, 96.3% and 97.3%, respectively; the specificity was 44.6%, 43.3% and 50.0%, respectively; the accuracy was 93.1%, 94.9% and 97.4%, respectively.

CONCLUSIONS

Our findings demonstrated that the optimized method could improve the positive detection rate of AMR and accuracy of decompression effect prediction. The evaluation for the decompression effect by optimized intraoperative monitoring can increase the immediate remission rate and reduce the delayed recovery rate.

Altered spontaneous brain activity in patients with hemifacial spasm: a resting-state functional MRI study

Resting-state functional magnetic resonance imaging (fMRI) has been used to detect the alterations of spontaneous neuronal activity in various neurological and neuropsychiatric diseases, but rarely in hemifacial spasm (HFS), a nervous system disorder. We used resting-state fMRI with regional homogeneity (ReHo) analysis to investigate changes in spontaneous brain activity of patients with HFS and to determine the relationship of these functional changes with clinical features. Thirty patients with HFS and 33 age-, sex-, and education-matched healthy controls were included in this study. Compared with controls, HFS patients had significantly decreased ReHo values in left middle frontal gyrus (MFG), left medial cingulate cortex (MCC), left lingual gyrus, right superior temporal gyrus (STG) and right precuneus; and increased ReHo values in left precentral gyrus, anterior cingulate cortex (ACC), right brainstem, and right cerebellum. Furthermore, the mean ReHo value in brainstem showed a positive correlation with the spasm severity (r = 0.404, p = 0.027), and the mean ReHo value in MFG was inversely related with spasm severity in HFS group (r = -0.398, p = 0.028). This study reveals that HFS is associated with abnormal spontaneous brain activity in brain regions most involved in motor control and blinking movement. The disturbances of spontaneous brain activity reflected by ReHo measurements may provide insights into the neurological pathophysiology of HFS.

Electrophysiologic investigation during facial motor neuron suppression in patients with hemifacial spasm: possible pathophysiology of hemifacial spasm: a pilot study

Objective

To evaluate the pathophysiological mechanism of hemifacial spasm (HFS), we performed electrophysiological examinations, such as supraorbital nerve stimulation with orbicularis oris muscle recording and lateral spread tests, after suppressing the patient's central nervous system by administering intravenous diazepam.

Methods

Six patients with HFS were recruited. Supraorbital nerve stimulation with orbicularis oris muscle recording and the lateral spread test were performed, followed by intravenous application of 10 mg diazepam to achieve facial motor neuron suppression. Subsequently, we repeated the two electrophysiological experiments mentioned above at 10 and 20 minutes after the patients had received the diazepam intravenously.

Results

Orbicularis oris muscle responses were observed in all patients after supraorbital nerve stimulation and lateral spread tests. After the diazepam injection, no orbicularis oris muscle response to supraorbital nerve stimulation was observed in one patient, and the latencies of this response were evident as a slowing tendency with time in the remaining five patients. However, the latencies of the orbicularis oris muscle responses were observed consistently in all patients in the lateral spread test.

Conclusion

Our results suggest that ectopic excitation/ephaptic transmission contributes to the pathophysiological mechanisms of HFS. This is because the latencies of the orbicularis oris muscle responses in the lateral spread test were observed consistently in the suppressed motor neuron in our patients.

'Is tinnitus accompanied by hemifacial spasm in normal-hearing patients also a type of hyperactive neurovascular compression syndrome? : A magnetoencephalography study

Background

Traditionally, tinnitus accompanied by hemifacial spasm has been considered a type of hyperactive neurovascular compression syndrome that is similar to hemifacial spasm alone because of the anatomically close relationship between the facial nerve and cochlear nerve as well as the hyperactive clinical nature.

Methods

Participants were 29 subjects who presented with hemifacial spasm and neuroradiological evidence of vascular compression of the cranial (facial/cochlear) nerve. We used magnetoencephalography (MEG) to estimate the activity of the cochlear nerve in patients with and without tinnitus on the ipsilateral side. We compared the difference in the latency and the ratio of the equivalent current dipole (ECD) strength between the ipsilateral and contralateral sides of the spasm and tinnitus.

Results

Cochlear nerve activity in patients with tinnitus was increased with a shorter latency (p = 0.016) and stronger ECD strength (p = 0.028) compared with patients without tinnitus.

Conclusion

The MEG results from normal-hearing patients who had tinnitus accompanied by hemifacial spasm suggest that the hyperactivity of the auditory central nervous system may be a crucial pathophysiological factor in the generation of tinnitus in these patients. The neurovascular compression that causes sensory input from the pathologic facial nerve activity may contribute to this hyperactivity of the central auditory nervous system.

Facial nerve palsy and hemifacial spasm

Facial nerve lesions are usually benign conditions even though patients may present with emotional distress. Facial palsy usually resolves in 3-6 weeks, but if axonal degeneration takes place, it is likely that the patient will end up with a postparalytic facial syndrome featuring synkinesis, myokymic discharges, and hemifacial mass contractions after abnormal reinnervation. Essential hemifacial spasm is one form of facial hyperactivity that must be distinguished from synkinesis after facial palsy and also from other forms of facial dyskinesias. In this condition, there can be ectopic discharges, ephaptic transmission, and lateral spread of excitation among nerve fibers, giving rise to involuntary muscle twitching and spasms. Electrodiagnostic assessment is of relevance for the diagnosis and prognosis of peripheral facial palsy and hemifacial spasm. In this chapter the most relevant clinical and electrodiagnostic aspects of the two disorders are reviewed, with emphasis on the various stages of facial palsy after axonal degeneration, the pathophysiological mechanisms underlying the various features of hemifacial spasm, and the cues for differential diagnosis between the two entities.

Delayed recurrence of hemifacial spasm after successful microvascular decompression: follow-up results at least 5 years after surgery

BACKGROUND

Microvascular decompression (MVD) for hemifacial spasm (HFS) is regarded as the gold-standard treatment due to its efficacy and durability. However, some patients still suffer from delayed recurrence after initially successful MVD.In this study, we describe our clinical experience in a single institute following up initially successful MVD for HFS 5 or more years after surgery. We analyzed the probability of, risk/predisposing factors for, and timing of delayed recurrence.

METHODS

We retrospectively reviewed data from 587 patients meeting our inclusion criteria who underwent MVD for HFS from March, 1999, to June, 2006. We evaluated the time-dependent probability of recurrence and factors affecting delayed recurrence and time of recurrence.

RESULTS

The probability of delayed recurrence was 1.0, 1.7, and 2.9 % at 1 year, 2 years, and 5 years after surgery, respectively. Mean time to recurrence was 153.1 months (95 % confidence interval [151.4-154.9]). The probability of late recurrence was increased in patients with co-morbid arterial hypertension (p = 0.036). However, there was a trend towards an association of delayed recurrence with co-existence of young age, male gender, vein or VA offender, and experience of transient facial weakness.

CONCLUSIONS

Delayed recurrence of HFS after initially successful MVD is rare; however, there are patients who experience delayed recurrence more than 2 years after MVD, even until 5 years after MVD. Our results suggest that arterial hypertension contributes to late recurrence. We did not find a statistically significant relationship between recurrence and other putative risk/predisposing factors.

Trigeminal Neuralgia due to Vertebrobasilar Dolichoectasia

We presented a case of drug-resistant trigeminal neuralgia attributed to vertebrobasilar dolichoectasia, a rare condition characterized by enlargement, tortuosity, or elongation of intracranial arteries. Dolichoectatic vessels can cause dysfunction of cranial nerves through direct vascular compression. The relationships of vertebrobasilar dolichoectasia with the particularities of neurovascular conflict and images findings are discussed.

Glucose hypermetabolism in the thalamus of patients with hemifacial spasm

The purpose of this study was investigate functional alteration in the brains of patients with hemifacial spasm using positron emission tomography (PET). We studied cerebral glucose metabolism using PET with (18) F-fluorodeoxyglucose in 13 patients with right lateral hemifacial spasm and 13 with left lateral hemifacial spasm. All patients underwent 2 PET scans before treatment (active state) and after treatment (suppressive state) with the botulinum neurotoxin type A. At the time of the PET scans, the severity of the spasm was rated according to the Jankovic Disability Rating Scale. We also used magnetic resonance imaging to evaluate the grade of neurovascular compression in each patient using scores of 1 to 3 (1 = mild, 3 = severe). Fifty-two normal volunteers were examined as controls. Compared with controls, patients with right and left hemifacial spasm showed bilateral cerebral glucose hypermetabolism in the thalamus in both the active and suppressive states. However, thalamic glucose metabolism after the suppressive state was significantly reduced compared with that in the active state using region of interest analysis. There was a positive correlation between the severity of the spasm in the active state and the score of neurovascular compression (rs = 0.65) that was estimated using Spearman order correlation coefficient. We observed bilateral cerebral glucose hypermetabolism in the thalamus of patients with hemifacial spasm. The thalamic glucose hypermetabolism may be attributed to multiple sources, including afferent input from the skin and muscle spindle, antidromic conduction of the facial nerve, and secondary alteration in the central nervous system.

Prognostic value of intra-operative abnormal muscle response monitoring during microvascular decompression for long-term outcome of hemifacial spasm

The reliability of intra-operative abnormal muscle response (AMR) monitoring as an indicator of post-operative outcome in patients with hemifacial spasm (HFS) is under debate. The primary aim of this study was to evaluate the correlation between intra-operative AMR changes and long-term post-operative outcome. We monitored intra-operative AMR during microvascular decompression (MVD) in consecutive patients with HFS (n = 104). Patients in this study were divided into two groups based on whether their AMR disappeared or persisted following MVD. Ninety patients were followed-up, and the mean duration from surgery to final follow-up examination was 3.7 years. Fourteen patients were lost to follow-up. AMR disappeared during surgery for 80 patients; of these, 74 achieved complete resolution of HFS, five had persistent HFS, and one patient developed a recurrence of HFS. Of the 10 patients with persistent AMR despite effective MVD, eight patients achieved complete resolution, one patient had persistent HFS, and one developed recurrent HFS. The long-term clinical outcome of HFS after MVD did not significantly correlate with intra-operative AMR changes (p = 0.791). Therefore, we suggest that intra-operative AMR monitoring may not be a reliable indicator of long-term post-operative outcome for HFS.

Hemifacial spasm due to a large distant ipsilateral posterior fossa meningioma

A rare case of hemifacial spasm due to an ipsilateral foramen magnum/clival meningioma is described. Magnetic resonance imaging demonstrated that the tumor was located distant to the cranial nerve VII/VIII complex. Resolution of the ipsilateral hemifacial spasm was noted after complete resection of the tumor. The mechanism of hemifacial spasm was likely due to displacement and distortion of the brain stem from the lesion distant to the cranial nerve VII/VIII complex. In our review of the literature this is the first reported case of an ipsilateral posterior fossa meningioma causing hemifacial spasm from indirect mass effect.

Hemifacial spasm as a feature of Chiari malformation: case report

BACKGROUND AND IMPORTANCE

Hemifacial spasm has rarely been described as one of the presenting features of Chiari I malformation. We present a case in which we found an association between the two in the absence of a basilar impression.

CLINICAL PRESENTATION

A case of a 39-year-old man who presented with a disabling hemifacial spasm and was found to have Chiari I malformation as the possible cause is described. A foramen magnum decompression successfully relieved the hemifacial spasm. The patient remains symptom free at 20 months after the operation.

CONCLUSION

Neurosurgeons may want to consider foramen magnum decompression as first-line surgical treatment for hemifacial spasm when it coexists with Chiari I malformation. Chiari I malformation should be considered one of the rare causes of hemifacial spasm.

Microneurovascular decompression in patients with hemifacial spasm caused by vascular compression of facial nerve at cisternal portion

BACKGROUND

Hemifacial spasm is commonly caused by arterial compression of the facial nerve. Although vascular compression usually occurs at the facial nerve exit zone, in some cases, the facial nerve is compressed more distally. We analyzed the clinical outcome of microneurovascular decompression in patients with hemifacial spasm caused by either distal or proximal compression.

METHOD

From September 1978 to March 2009, 2,137 patients underwent microneurovascular decompression for hemifacial spasm due to vascular compression of the facial nerve, including 2,022 patients (94.6%) with proximal compression, 101 patients (4.7%) with both proximal and distal (mixed) compression, and 14 patients (0.7%) with only distal compression.

FINDINGS

Complete remission of facial spasm occurred in 10 of 14 patients (71.4%) with compression of the cisternal portion, compared with 1,773 of 2,022 patients (87.7%) with proximal compression (P = 0.08) and 87 of 101 patients (86.1%) with mixed compression (P = 0.23). Permanent facial weakness occurred in one patient (7.1%) with compression of the cisternal portion, 18 patients (0.9%) with proximal compression, and one patient (1.0%) with mixed compression. Permanent hearing loss occurred in no patients with compression of the cisternal portion, 29 patients (1.4%) with proximal compression, and three patients (3.0%) with mixed compression.

CONCLUSIONS

Outcomes after microneurovascular decompression for hemifacial spasm with compression of the cisternal portion were not statistically different than with proximal compression of the facial nerve. When the clinical diagnosis of hemifacial spasm is confirmed and vascular compression is seen only in the cisternal portion of the facial nerve, microneurovascular decompression for these patients provides outcomes similar to those with proximal compression of the facial nerve.

Auditory evoked blink reflex and posterior auricular muscle response: observations in patients with HFS and PFS

Our goal was to investigate the characteristics of the auditory brainstem reflexes in patients with hemifacial spasm (HFS) and postparalytic facial syndrome (PFS). The spasm activities and responses by supraorbital and auditory stimuli were recorded from the orbicularis oculi, the posterior auricular and the mentalis muscles in 27 HFS and 21 PFS patients. The results were compared with those of 20 controls. Blink reflex (BR) was obtained by supraorbital stimulation in normal controls and on both sides of HFS and PFS patients whereas sound evoked bilateral auditory blink reflex (ABR) in 96.3%, 90.5% and 100%, respectively. Both BR and ABR showed synkinetic spread on symptomatic sides in all patients. The posterior auricular muscle response (PAMR) was observed bilaterally in 59.3%, 42.9% and 75.0% of groups, respectively. However, there was no synkinetic spread of PAMR. Since PAMR does not show synkinetic spread even in the presence of synkinetic spread of ABR and BR, we may suggest that a distal origin may be responsible of the synkinetic spread, or PAM is probably governed by a smaller nucleus in the brainstem. Thus it may be speculated that its excitability is insufficient to stimulate the ABR nucleus, whereas the reverse process is possible.

Neurovascular compression in painful tic convulsif

This article describes the case of a 67-year-old woman who presented with a typical left hemifacial spasm of 8-month duration. After 2 months, she experienced lacinating and sharp shock-like pain in the left side of her face affecting the V1 and V2 territories and a discrete attenuation of nauseous reflex on the left side. CT angiography and MRI revealed significant compression of left cranial nerves V, VII, VIII, IX and X by a giant and tortuous vertebro-basilar arterial complex. This case illustrates the nonlinearity of the relationship between the presence of the stressor factor and the actual manifestation of the disease.

Time course of symptom disappearance after microvascular decompression for hemifacial spasm

OBJECTIVE

This study is to investigate time course of symptom disappearance in patients whose spasm relieved completely after microvascular decompression (MVD).

METHODS

Of 115 patients with hemifacial spasm (HFS) who underwent MVD from April 2003 to December 2006, 89 patients who had no facial paralysis after operation and showed no spasm at last follow-up more than 1.5 years after operation were selected. Symptom disappearance with time after MVD was classified into type 1 (symptom disappearance right after operation), type 2 (delayed symptom disappearance) and type 3 (unusual symptom disappearance). Type 2 was classified into type 2a (with postoperative silent period) and type 2b (without silent period).

RESULTS

Type 1, type 2a, type 2b and type 3 were 38.2%, 48.37%, 12.4% and 1.1%, respectively. Delayed disappearance group (type 2) was 60.7%. Post-operative symptom duration in all cases ranged from 0 to 900 days, average was 74.6 days and median was 14 days. In case of type 2, average post-operative symptom duration was 115.1 days and median was 42 days. Five and 3 patients required more than 1 year and 2 years, respectively, until complete disappearance of spasm. In type 2a, postoperative silent period ranged from 1 to 10 days, with an average of 2.4 days.

CONCLUSION

Surgeons should be aware that delayed symptom disappearance after MVD for HFS is more common than it has been reported, silent period can be as long as 10 days and time course of symptom disappearance is various as well as unpredictable.