Correlation between idiopathic hemifacial spasm and the MRI characteristics of the vertebral artery

Analysis of risk factors related to the progression rate of hemifacial spasm

Introduction

Although there have been many researches on the etiology and risk factors with the onset of hemifacial spasm, researches on the risk factors related to progression rate are limited. This study aims to analyze the risk factors related to the progression rate of hemifacial spasm.

Methods

The study enrolled 142 patients who underwent microvascular decompression for hemifacial spasm. Based on the duration and severity of symptoms, patients were classified into rapid progression group and slow progression group. To analyze risk factors, univariate and multivariate logistic regression analyses were conducted. Of 142 patients with hemifacial spasm, 90(63.3%) were classified as rapid progression group, 52(36.7%) were classified as slow progression group.

Results

In the univariate analysis, there were significant statistical differences between the two groups in terms of age of onset (P = 0.021), facial nerve angle (P < 0.01), hypertension (P = 0.01), presence of APOE ε4 expression (P < 0.01) and different degrees of brainstem compression in the Root Entry Zone (P < 0.01). In the multivariable analyses, there were significant statistical differences between the two groups in terms of age of symptom onset (P < 0.01 OR = 6.591), APOE ε4 (P < 0.01 OR = 5.691), brainstem compression (P = 0.006 OR = 5.620), and facial nerve angle (P < 0.01 OR = 5.758). Furthermore, we found no significant correlation between the severity of facial spasms and the progression rate of the disease (t = 2.47, P = 0.12>0.05).

Conclusion

According to our study, patients with facial nerve angle ≤ 96.5°, severer compression of the brainstem by offending vessels, an onset age > 45 years and positive expression of APOE ε4, may experience faster progression of hemifacial spasm.

Evaluating magnetic resonance imaging characteristics and risk factors for hemifacial spasm

PURPOSE

The specific neurovascular compression (NVC) event responsible for the symptomatic manifestation of hemifacial spasm (HFS) remains difficult to assess accurately using magnetic resonance imaging (MRI). We aim to evaluate the MRI characteristics of HFS.

METHOD

We retrospectively included patients with HFS and divided them into a test group (n = 186) and a validation group (n = 28). The presence, severity, and offending vessel type of NVC in each portion, and the orientation of the offending vessel around the facial nerve, were recorded. Conditional logistic regression analyses were performed to evaluate correlations using test group. The validation group was used to verify whether our findings improved diagnostic performance.

RESULTS

Deformity in the proximal cisternal segment was significantly correlated with HFS occurrence (odds ratio [OR]: 256.58, p = .002), whereas contact was not (p = .233). Both contact and deformity in the root detachment point (OR: 19.98 and 37.22, p < .001 and p = .013, respectively) or attached segment (OR: 4.99 and 252.52, p = .001 and p < .001, respectively) were significantly correlated with HFS occurrence. Our findings improved specificity, positive predictive value, and accuracy of diagnosis than conventional diagnostic methods. The vertebral artery predominantly compress the facial nerve in the inferior-anterior position, the anterior inferior cerebellar artery predominantly in the inferior position, the posterior inferior cerebellar artery predominantly in the inferior position, vein predominantly in the posterior-superior position.

CONCLUSIONS

This study further demonstrates that within the susceptible portion of facial nerve, different portions of the nerve respond differently to NVC. Each offending vessel has its own preferred conflict orientation. Our study offers reference for neurosurgeons in diagnosis and treatment.

The Superior Cerebellar Artery: Variability and Clinical Significance

The superior cerebellar artery (SCA) arises from the distal part of the basilar artery and passes by the oculomotor, trochlear, and trigeminal nerves. SCA is known to play a crucial role in the development of trigeminal neuralgia. However, due to its anatomical variability, it may also trigger other neurovascular compression (NVC), including hemifacial spasm, oculomotor nerve palsy, and ocular neuromyotonia. Additionally, it may be associated with ischemic syndromes and aneurysm development, highlighting its clinical significance. The most common anatomical variations of the SCA include duplication, a single vessel origin from the posterior cerebral artery (PCA), and a common trunk with PCA. Rarely observed variants include bifurcation and origin from the internal carotid artery. Certain anatomical variants such as early bifurcation and caudal course of duplicated SCA trunk may increase the risk of NVC. In this narrative review, we aimed to examine the impact of the anatomical variations of SCA on the NVCs based on papers published in Pubmed, Scopus, and Web of Science databases with a snowballing approach. Our review emphasizes the importance of a thorough understanding of the anatomical variability of SCA to optimize the management of patients with NVCs associated with this artery.

The Underlying Pathogenesis of Neurovascular Compression Syndromes: A Systematic Review

Neurovascular compression syndromes (NVC) are challenging disorders resulting from the compression of cranial nerves at the root entry/exit zone. Clinically, we can distinguish the following NVC conditions: trigeminal neuralgia, hemifacial spasm, and glossopharyngeal neuralgia. Also, rare cases of geniculate neuralgia and superior laryngeal neuralgia are reported. Other syndromes, e.g., disabling positional vertigo, arterial hypertension in the course of NVC at the CN IX-X REZ and torticollis, have insufficient clinical evidence for microvascular decompression. The exact pathomechanism leading to characteristic NVC-related symptoms remains unclear. Proposed etiologies have limited explanatory scope. Therefore, we have examined the underlying pathomechanisms stated in the medical literature. To achieve our goal, we systematically reviewed original English language papers available in Pubmed and Web of Science databases before 2 October 2021. We obtained 1694 papers after eliminating duplicates. Only 357 original papers potentially pertaining to the pathogenesis of NVC were enrolled in full-text assessment for eligibility. Of these, 63 were included in the final analysis. The systematic review suggests that the anatomical and/or hemodynamical changes described are insufficient to account for NVC-related symptoms by themselves. They must coexist with additional changes such as factors associated with the affected nerve (e.g., demyelination, REZ modeling, vasculature pathology), nucleus hyperexcitability, white and/or gray matter changes in the brain, or disturbances in ion channels. Moreover, the effects of inflammatory background, altered proteome, and biochemical parameters on symptomatic NVC cannot be ignored. Further studies are needed to gain better insight into NVC pathophysiology.

Complex Neurovascular Syndromes: Is the Compressing Vessel Alone the Culprit?

Objective To describe and correlate the clinical, radiological, and intraoperative findings in patients with refractory neurovascular syndromes (NVS) not responding to conventional medical management and to determine the surgical outcome of the microvascular decompression (MVD) procedure.

Methods Medical records of 17 patients with NVS (trigeminal neuralgia [TN] = 14 and hemifacial spasm = 3) who underwent surgery for symptom relief from January 2018 to July 2021 with follow-up data (1–36 months) were retrospectively analyzed. Patient demographics (age, sex), clinical features (site, duration of symptoms, distribution), magnetic resonance imaging (MRI) findings, micro-neurosurgical details (type of surgery, obstructive vessel), and postoperative outcome and complications were recorded.

Statistical Analysis Descriptive analysis was performed. Variables were presented as either mean and standard deviation or frequency and percentages.

Results The mean (standard deviation) age of patients in our study cohort was 52.6 (12.2) years. TN was common in females (64.3%). The mean duration of symptoms was longer in patients with hemifacial spasms than in patients with TN (3.3 vs. 2.7 years). While the right side was commonly affected in TN (64.3%), the left side was common in hemifacial spasm (66.7%). Most common neuralgia symptoms were distributed along the V2V3 (maxillary and mandibular division) branches (42.9%). MRI revealed neurovascular conflict in nine patients, epidermoid tumor in three patients, classical vestibular schwannoma in two patients, and short cisternal segments in three patients. Intraoperatively, superior cerebellar artery was the main offending vessel in TN followed by anterior inferior cerebellar artery (AICA) and venous compression, while tortuous vertebral artery and AICA along with thickened entangled arachnoid were seen in hemifacial spasms. Almost all patients (88.2%) reported immediate postoperative complete pain relief. One patient died secondary to chest infection after a month.

Conclusion Arachnoid entanglement around the neurovascular bundle along with vascular compression over the cranial nerves is the main cause of NVS. Advanced micro-neurosurgical techniques used in MVD achieve excellent outcomes with improved quality of life. However, identifying the refractory NVS not responding to conventional medical management and early surgical management are paramount.

Anatomical deviations of vertebral artery in hemifacial spasm: a quantitative study

PURPOSE

There exist different opinions on whether the anatomical laterality of vertebral artery (VA) is related to the unilateral onset of hemifacial spasm (HFS). In this study, we intended to qualitatively explore the potential correlation between the anatomical deviations of VA and the clinical characteristics of HFS.

METHODS

Two hundred and forty patients who underwent microvascular decompression for HFS between January 2018 and December 2019 were recruited. Clinical data including medical records and preoperative MRI images were retrospectively reviewed. A score system was specially designed for VAs to illustrate their distribution, and a score-weighted cross-sectional area of VA was proposed to represent the relative thickness of VA on each side. Then, the anatomical deviations of VA were comparatively analyzed between the symptomatic side and asymptomatic side and between VA-involved cases and non-VA-involved cases.

RESULTS

The score and weighted cross-sectional area (WCSA) of VA in symptomatic side were significantly greater than those in asymptomatic side (P = 0.000, P = 0.000). And in symptomatic side, the score and WCSA of VA in VA-involved cases were significantly greater than those in non-VA-involved cases (P = 0.000). Moreover, with higher score (P = 0.000) and greater WCSA (P = 0.001) on the left side, the VA-involved cases showed a preference (74%) of left HFS.

CONCLUSIONS

In HFS, the symptomatic side tends to have an ipsilaterally deviated and relatively larger VA, especially in VA-involved cases. And it is the VA-involved cases that are prone to have a prevalence of left HFS, but not the non-VA-involved cases.

Morphological characteristics of the vertebrobasilar artery system in patients with hemifacial spasm and measurement of bending length for evaluation of tortuosity

OBJECTIVE

Dominant vertebral artery (DVA), tortuosity, and elongation of the vertebrobasilar artery system are frequently observed in hemifacial spasm (HFS). However, the morphological characteristics of the tortuosity of vertebrobasilar artery system have not yet been elucidated. In this study, we presented a novel method for the measurement of the bending length (BL) of the basilar artery(BA) or vertebral artery (VA) to assess the tortuosity of vertebrobasilar artery system in HFS patients.

METHODS

The demographic and morphological characteristics of 135 patients with HFS admitted to the neurosurgical department to undergo microvascular decompression (MVD) were analyzed in this retrospective study. The BL was defined to appraise the tortuous degree of the vertebrobasilar artery system, and according to the BL value, the patients with HFS were divided into two groups: tortuous vertebrobasilar artery (TVA) and non-TVA groups. Additionally, the vessels responsible for HFS were analyzed based on the results of magnetic resonance imaging (MRI) of the two groups. The patients were followed up for 2-6 years post-discharge, and the effect of MVD operation was compared between the two groups.

RESULTS

DVA was detected in 60.2% of HFS patients; the incidence of left-sided HFS in the TVA group was significantly higher than that in the non-TVA group (P = 0.013). The proportion of multiple responsible vessels in the TVA group was 68.4% (54/79), while that in the non-TVA group was 4.1% (2/49). The complication rate of the two groups was different, and that of the tortuous group was higher than that of the non-tortuous group.

CONCLUSIONS

The morphological characteristics of the vertebrobasilar artery system in patients with HFS were complex. The measurement of BL is an easy and reliable tool to assess the tortuosity of the vertebrobasilar artery system in HFS patients.

Evaluation of pre-operative neuroimaging characteristics in patients with primary hemifacial spasm as a prognostic factor of microvascular decompression

OBJECTIVE

The aim of this study was to explore the possible pathogenesis of primary hemifacial spasm (HFS) according to the performances of preoperative high-resolution magnetic resonance (MR) sequence and investigate the correlations between the neuroimaging parameters and the prognosis of microvascular decompression (MVD).

METHODS

106 patients with HFS and 121 age-matched and gender-matched healthy controls (HCs) were included in this study. Electronic medical records and neuroimaging data were collected. The facial-nerve angle, cross-sectional area of CPA cistern and length of the cistern segment of the facial nerve were measured on affected side and unaffected as well as healthy individuals. The receiver operating characteristic curve was used for assessing the predictive performances.

RESULTS

100 patients achieved complete relief postoperatively. 13 of the 100 complete relief patients developed a relapse in the follow-up. The preoperative facial-pontine angle and cross-sectional area of the CPA cistern on the affected side was significantly smaller than the unaffected side and HC. The facial-pontine angle and the cross-sectional area of the CPA cistern was significantly smaller in recurrent group than the non-recurrent group. The AUC value of both facial-pontine angle and cross-sectional area of the CPA cistern were over 0.7.

CONCLUSION

Small facial-nerve angle and cross-sectional area of CPA cistern may be regarded as the possible pathogenesis of primary HFS. The measurement of facial-nerve angle and cross-sectional area of CPA cistern preoperatively might be used to predict the surgical effect of MVD.

Mechanism underlying cranial nerve rhizopathy

The cranial nerve rhizophathy, commonly presented with trigeminal neuralgia (TN) or hemifacial spasm (HFS), is a sort of hyperexcitability disorders with higher incidence in senior Asian. In this paper, a novel hypothesis on the pathogenesis is proposed and with which some clinical phenomena are explained. In those with crowded cerebellopontine angle in anatomy, the cranial nerve root and surrounding vessel are getting closer and closer to each other with aging and finally the neurovascular conflict happens. As the interfacial friction associated with pulse, the nerve incurs demyelination. Since this pathological change develops to a certain degree, some transmembrane proteins emerge from the nerve due to a series of signaling pathway mediated by inflammatory cytokines. Among them, voltage-gated (Na_v1.3) and mechanosensitive (Piezo2) ion channels may play the important role. With pulsatile compressions, the Piezo2 drives the resting potential toward depolarization forming a state of subthreshold membrane potential oscillation. Under this condition, just an appropriate pressure can make the membrane potential easy to reach threshold and activate the sodium channel, eventually generating conductible action potentials from the axon. When these ectopic action potentials propagate to the central nerve system, an illusion of sharp pain is perceived; while to the nerve-muscle junctions, an attack of irregular muscle constriction occurs. This hypothesis can well explain the symptomatic manifestation of paroxysmal attacks aroused by emotions. When we get nervous or excited, our heart rate and blood pressure alter correspondingly, which may give rise to "a just right pressure" - with specific frequency, amplitude and angle - impacting the suffered nerve to reach the threshold of impulse ignition. After a successful microvascular decompression surgery, the trigger is gone (there is no compression anymore) and the symptom is alleviated. While the postoperative recurrence could be attributable to Teflon granuloma development if had been placed improperly - for this nerve root has been susceptible no matter to arteries or to neoplasms. Besides, it may illustrate the clinical phenomenon that secondary TN or HFS cases are seldom caused by schwannoma: with a proliferative sheath, the nerve root is actually insulated. By contrast, not all neurovascular contacts can lead to the onset: it demands an exclusive extent of demyelination firstly.

Microvascular decompression for hemifacial spasm associated with distinct offending vessels: A retrospective clinical study

OBJECTIVE

To investigate the surgical effects and complications of microvascular decompression (MVD) for hemifacial spasm (HFS) based on different offending vessels, and report our surgical experience of HFS patients related to vertebral artery.

PATIENTS AND METHODS

MVDs performed in Nanjing Drum Tower Hospital between January 1, 2014 and December 31, 2017 were retrospectively studied, and 1152 patients with HFS were split into two groups in accordance with the offending vessels.

RESULTS

954 patients with HFS caused by small vascular compression were classified as Group A. 849 patients got cured immediately after MVD, while delayed resolution was identified in 101 patients. 4 patients were not relieved and 4 were relapsed during the follow-up period. We observed 76 cases of delayed facial paralysis, 7 cases of hearing loss, 2 hoarseness and 3 cases of CSF leakage after surgery. In Group B, 198 patients displayed HFS associated with the vertebral artery (VA). 144 cases were spasm free after surgery and 51 patients had a delayed resolution. 3 patients were not significantly ameliorated and 2 were relapsed during the follow-up period. The major postoperative complications included facial paralysis in 28 patients, hearing loss in 4 and hoarseness and dysphagia in 3. The two groups showed no operative death.

CONCLUSIONS

For the patients with HFS related to VA, the delayed cure rate and the incidence of postoperative cranial nerve complications were higher than HFS attributed to small vascular compression. And the two groups were not different in the long-term outcome and the incidence of permanent cranial nerve complications.

Microvascular decompression for hemifacial spasm associated with the vertebral artery

The aim of this study was to discuss the baseline characteristics of hemifacial spasm (HFS) associated with the vertebral artery (VA) and evaluate microvascular decompression (MVD) as a surgical treatment of the associated HFS. From February 2010 to February 2015, 118 consecutive patients with HFS underwent MVD. Of these, 29 cases of HFS were associated with VA, this series was compared with the remaining non-VA-associated HFS. Of the 29 cases of VA-associated HFS, the VA was directly compressing the root exit zone (REZ) in eight cases. In the other 21 cases, the VA contacted REZ indirectly via its branches. The symptoms were completely relieved in 26 cases (89.7%) and partially relieved in another two cases (6.9%). Between the VA-associated group and non-VA-associated group, no statistically significant difference existed in the surgical results. VA-associated HFS is not a rare condition. For all cases of VA-associated HFS, indirect compression due to VA was more common. MVD for VA-associated HFS still can achieve good results.

Flatness of the infratentorial space associated with hemifacial spasm

BACKGROUND

Whether a difference in morphology of the infratentorial space is associated with hemifacial spasm is not well understood. The aim of this study was to analyze the three-dimensional conformation of the infratentorial space and evaluate any possible contribution of morphological characteristics to the development of neurovascular compression leading to hemifacial spasm.

METHODS

We enrolled 25 patients with hemifacial spasm and matched them by age and sex to controls. The extent of the three-dimensional axes and the volume of the infratentorial space were measured using image analysis software for three-dimensional MRI. We evaluated the correlation between a morphological difference in the infratentorial space and changes in vascular configuration in the brain stem.

RESULTS

We found no statistical difference in volumetric analyses. The mean aspect ratio on the coronal plane (the ratio of the Z to X extent) of the infratentorial space in patients with hemifacial spasm was significantly lower (p < 0.01) than that in controls, as was the mean aspect ratio on the sagittal plane (the ratio of Z to Y extent, p < 0.01). A smaller sagittal aspect ratio was correlated (p < 0.05) with greater lateral deviation of the basilar artery.

CONCLUSIONS

Our results suggest that flatness of the superior-inferior dimension of the infratentorial space is an anatomical feature that characterizes patients with hemifacial spasm. We hypothesize that this unique structural variation may exaggerate the lateral deviation of the vertebrobasilar arteries due to arteriosclerosis and exacerbate the space competition among vessels and cranial nerves.

Management of symptomatic hemifacial spasm or trigeminal neuralgia

Hemifacial spasm (HFS) or trigeminal neuralgia (TN) is a kind of hyperactivity disorder of cranial nerves caused by vascular compression. However, sometimes, the disease may arise from nerve damage produced by tumors, which was called as symptomatic HFS/TN. Until now, little is known about the exact mechanism and the necessity of microvascular decompression (MVD) regarding the tumor-induced HFS/TN, which is necessary to be retrospectively analyzed in a considerable sample. Among the 4021 patients who underwent MVD in our department between 2006 and 2014, 44 were finally diagnosed as symptomatic HFS or TN. These patients were focused in this study and their clinical features as well as intraoperative findings and postoperative outcomes were retrospectively investigated. Data analysis exhibited the symptomatic HFS/TN cases accounted for 1.1 % in the study, which were caused by epidermoid in 18 (40.9 %) and meningioma in 15 (34.1 %) followed by neuroma in 7 (15.9 %) as well as aneurysm in 2 (4.5 %) and arteriovenous malformation in 2 (4.5 %). Compared to those with idiopathic HFS/TN, younger females were more susceptible (p < 0.05). After resection of the neoplasm, the offending vessel was identified in 26 (59.1 %), which were followed by MVD process. Postoperatively, the symptoms relief rate was 88.6 %. Our study showed that surgical management of patients with symptomatic HFS/TN may lead to a satisfactory result, yet those primary lesions should be removed firstly. In some cases, a microvascular decompression process might be unnecessary afterward, but the entire nerve root should be checked to exclude any vessel in contact with.

Upregulation of Nav1.8 in demyelinated facial nerves might be relevant to the generation of hemifacial spasm

Our previous studies demonstrated that the abnormal muscle response could vanish when the ipsilateral superior cervical ganglion was removed and reappear when norepinephrine was dripped at the neurovascular conflict site. Evidentially, we believed that the mechanism of hemifacial spasm should involve emersion of ectopical action potential in the compressed facial nerve fibers. As the action potential is ignited by ion channel opening, we focused on Nav1.8 that has been found overexpressed in peripheral nerve while damaged. In this study, Moller model was adopted, 20 Sprague-Dawley rats underwent drip of norepinephrine, and the abnormal muscle response wave was monitored in 14 rats. Antibodies against unique epitopes of the α subunit of sodium channel isoforms were used to detect the Nav1.8 neuronal isoforms, and the immunohistochemistry showed strong staining in 13 rats, which were all in the abnormal muscle response positive group (P < 0.05). Accordingly, we concluded that the substance of hemifacial spasm is an ectopic action potential that emerged on the damaged facial nerve, which might be coupled by Nav1.8.

Characteristic anatomical conformation of the vertebral artery causing vascular compression against the root exit zone of the facial nerve in patients with hemifacial spasm

BACKGROUND

Hemifacial spasm (HFS) is caused by tortuous offending vessels near the facial nerve root exit zone. However, the definitive mechanism of offending vessel formation remains unclear. We hypothesized that vascular angulation and tortuosity, probably caused by uneven vertebral artery blood flow, result in vascular compression of the facial nerve root exit zone.

METHODS

The authors observed two anatomical characteristics of the vertebrobasilar arterial system in 120 subjects in the surgical group and 188 controls. The presence of the dominant vertebral artery (DVA) and laterality of the vertebrobasilar junction (VBJ) were observed. We also analyzed the morphological characteristics of the surgical group showing the presence of DVA. The morphological characteristics were classified into three types: type I had the VBJ and DVA on the same side, type II had the VBJ within 2 mm of the midline, and type III had the VBJ opposite the DVA.

RESULT

The DVA was more prevalent in the surgical group than in the control group (71 % versus 54 %, P < 0.05). The surgical group patients with HFS on the left were more likely to have a DVA on the left (P < 0.05) and with HFS on the right were more likely to have a DVA on the right (P < 0.01) compared with controls. The direction of the VBJ was more common on the same side as the DVA, which corresponds with the laterality of the HFS. In the surgical group with the DVA and HFS on the same side, type I was predominant, but in the surgical group with a contralateral DVA and HFS, type III was predominant.

CONCLUSION

The presence of a DVA and shifting of the VBJ on the same side plays a role in the angulation and tortuosity of vessels in the perivertebrobasilar junction, resulting in neurovascular compression of the facial nerve root exit zone and thereby causing HFS.

Delayed relief of hemifacial spasm after microvascular decompression: can it be avoided?

BACKGROUND

Although microvascular decompression (MVD) surgery has been widely accepted as an effective treatment for hemifacial spasm (HFS), delayed relief cases have been frequently reported. Therefore, the value of an immediate redo MVD should be discussed.

METHODS

This study included 1,435 HFS patients who underwent MVD with intraoperative abnormal muscle response (AMR) monitoring from 2011 through 2013 at XinHua Hospital. These cases were analyzed retrospectively with emphasis on the postoperative outcomes and introaperative findings.

RESULTS

After MVD, 1,384 HFS patients obtained relief immediately. The 51 unrelieved patients underwent AMR monitoring again the next day; this was positive in 48 and negative in 3 patients. These three patients with negative AMR obtained relief spontaneously within a week. Among the 48 positive patients, 31 and 11 were underwent redo MVD within a week and 5-22 months, respectively, and all achieved relief after the second operation. Of the six remainig patients, two obtained relief within 2 months and 4 remained unchanged in the up-to-3-year's follow-up period. In redo MVDs, insufficient decompression of the facial nerve accounted for the failure. Finally, in this database, the immediate postoperative cure rate was 96.4 %; with earlier redo MVD, the final cure rate could be increased to 99.9 %.

CONCLUSIONS

Despite being a reasonable remedy for HFS in the hands of an experienced neurosurgeon, sometimes small vessels can be missed while managing the main offending arteries during MVDs, which might account for the delayed relief. Therefore, reexamination of the AMR is necessary for unimproved patients; if a positive result is recorded, an immediate redo MVD is suggested.

Hemifacial spasm and neurovascular compression

Hemifacial spasm (HFS) is characterized by involuntary unilateral contractions of the muscles innervated by the ipsilateral facial nerve, usually starting around the eyes before progressing inferiorly to the cheek, mouth, and neck. Its prevalence is 9.8 per 100,000 persons with an average age of onset of 44 years. The accepted pathophysiology of HFS suggests that it is a disease process of the nerve root entry zone of the facial nerve. HFS can be divided into two types: primary and secondary. Primary HFS is triggered by vascular compression whereas secondary HFS comprises all other causes of facial nerve damage. Clinical examination and imaging modalities such as electromyography (EMG) and magnetic resonance imaging (MRI) are useful to differentiate HFS from other facial movement disorders and for intraoperative planning. The standard medical management for HFS is botulinum neurotoxin (BoNT) injections, which provides low-risk but limited symptomatic relief. The only curative treatment for HFS is microvascular decompression (MVD), a surgical intervention that provides lasting symptomatic relief by reducing compression of the facial nerve root. With a low rate of complications such as hearing loss, MVD remains the treatment of choice for HFS patients as intraoperative technique and monitoring continue to improve.

Microvascular decompression surgery: surgical principles and technical nuances based on 4000 cases

BACKGROUND

As an etiological treatment of trigeminal neuralgia (TN) and hemifacial spasm (HFS), microvascular decompression (MVD) has been popularized around the world. However, as a functional operation in the cerebellopontine angle (CPA), this process can be risky and the postoperative outcomes might not be good enough sometimes.

OBJECTIVE

In order to obtain a better result with less complication, this surgery should be further addressed.

METHODS

With experience of more than 4000 MVDs, we have gained knowledge about the operative technique. Through abundant intraoperative photos, each step of the procedure was demonstrated in detail and the surgical strategy was focused.

RESULTS

The principle of MVD is to separate the nerve-vessel confliction rather than isolate it with prostheses. A prompt identification of the conflict site is important, which hinges on a good exposure. A satisfactory working space can be established by an appropriate positioning of the patient's head and a proper craniectomy as well as a rational approach. A sharp dissection of arachnoids leads to a maximal visualization of the entire intracranial course of the nerve root. All the vessels contacting the trigeminal or facial nerve should be treated. Intraoperative electrophysiological mentoring is helpful to distinguish the offending artery for hemifacial cases.

CONCLUSION

MVD is an effective treatment for the patient with TN or HFS. Immediate relief can be achieved by an experienced neurosurgeon with good knowledge of regional anatomy. A safe surgery is the tenet of MVD, and accordingly, no single step of the procedure should be ignored.

Microvascular decompression on patients with trigeminal neuralgia caused by ectatic vertebrobasilar artery complex: technique notes

BACKGROUND

Due to its anatomical features, the vertebrobasilar artery complex (VBA) seldom contributes to the neurovascular conflict in patient with trigeminal neuralgia (TN). However, once it offends the trigeminal root, this large artery is really difficult to manipulate during microvascular decompression (MVD) surgery. Therefore, the surgical strategy for such cases needs to be detailed in order to obtain a satisfactory outcome.

METHODS

From 2009 through 2011, 475 consecutive TN patients underwent MVDs in our department. Among them, ten were found in which an ipsilateral deviating ectatic vertebrobasilar artery complex (VBA) offended the trigeminal nerve. Those cases were focused on in this study and each operation was analyzed retrospectively.

RESULTS

During the operation, the vertebral artery was regarded as the direct culprit in six (60 %) patients, while the basilar artery in four (40 %). As companions, some smaller vessels were also observed to be close to the nerve, including the superior cerebellar artery (SCA) in five, veins in two and anterior inferior cerebellar artery (AICA) in two. The neurovascular conflict was discovered in the cisternal segment of the trigeminal root in eight, while in the root entry zone (REZ) in two. In six out of the ten cases, the affected nerves were demonstrated to be squeezed towards the tentorium by the ectatic VBA. Postoperatively, the symptom of pain totally disappeared immediately in eight (80 %) patients, while it was relieved apparently in two (20 %). During the follow-up period of 3-30 months, no recurrence or complication was found, except for one patient who had numbness of the face.

CONCLUSION

With a proper strategy, MVD is probably the most effective therapy for the TN cases caused by ectatic vertebrobasilar artery complex. The substance of the surgery is to withdraw the proximal vertebral artery caudally via a lateroinferior cerebellar approach.