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

Bridge-layered decompression technique for vertebral artery-involved hemifacial spasm: technical note

BACKGROUND

Hemifacial spasm (HFS) is most effectively treated with microvascular decompression (MVD). However, there are certain challenges in performing MVD for HFS when the vertebral artery (VA) is involved in compressing the facial nerve (VA-involved). This study aimed to introduce a "bridge-layered" decompression technique for treating patients with VA-involved HFS and to evaluate its efficacy and safety to treat patients with HFS.

METHODS

A single-center retrospective analysis was conducted on the clinical data of 62 patients with VA-involved HFS. The tortuous trunk of VA was lifted by a multi-point "bridge" decompression technique to avoid excessive traction of the cerebellum and reduce the risk of damage to the facial-acoustic nerve complex. To fully decompress all the responsible vessels, the branch vessels of VA were then isolated using the "layered" decompression technique.

RESULTS

Among the 62 patients, 59 patients were cured immediately after the surgery, two patients were delayed cured after two months, and one had occasional facial muscle twitching after the surgery. Patients were followed up for an average of 19.5 months. The long-term follow-up results showed that all patients had no recurrence of HFS during the follow-up period, and no patients developed hearing loss, facial paralysis, or other permanent neurological damage complications. Only two patients developed tinnitus after the surgery.

CONCLUSION

The "bridge-layered" decompression technique could effectively treat VA-involved HFS with satisfactory safety and a low risk of hearing loss. The technique could be used as a reference for decompression surgery for VA-involved HFS.

Mapping trends in hemifacial spasm research: bibliometric and visualization-based analyses of the Web of Science Core Collection

Hemifacial spasm (HFS) is a common cranial nerve disease. In HFS research, we conducted a bibliometric analysis to examine the development and research trends. A retrieval of HFS studies published between 2011 and 2022 was performed from the Web of Science Core Collection in September 2022. Two scientometric tools were used to perform bibliometric and visualization-based analyses: VOSviewer and CiteSpace. Bibliometric analysis of 1461 studies published between 2011 and 2022 was carried out using data from 444 journals, 6021 authors, 1732 institutions, and 76 countries/regions. China, the USA, Japan, and South Korea were four key contributors to this study. Shanghai Jiaotong University was the major institution with the larger number of publications. Li Shiting was the most prolific author. Jannetta PJ was the most co-cited author. World Neurosurgery was the top prolific journal. Journal of Neurosurgery was the top co-cited journal. The top five keywords were hemifacial spasm, microvascular decompression, trigeminal neuralgia, surgery, and neurovascular compression. This study examines the research trends in global scientific research on HFS over the last decade. Researchers interested in learning more about current trends and novel research frontiers in this area can benefit from the study.

Bridge technique for hemifacial spasm with vertebral artery involvement: 2-Dimensional operative video

Microvascular decompression for hemifacial spasm (HFS) associated with the vertebral artery (VA) is more challenging than that for small arteries. Atherosclerotic VA and tortuous VA are associated with a low success rate and high incidences of complications. Artery relocation employing a Teflon sling is helpful for small arteries. However, a different decompression technique should be considered in VA-related HFS due to the stiffness of the offending artery. With our simple decompression technique providing a secure transposition that can be performed even in the narrow cistern, a rigid Teflon bar is inserted to hold up all offending vessels between the pontine surface and the cerebellar flocculus (the bridge technique). This simple technique easily creates a free space over the root entry zone (REZ), reduces surgical manipulation compared to conventional artery relocation with a Teflon sling, and provides more secure nerve decompression than inserting Teflon pledgets on the REZ. The critical factors for successfully performing the bridge technique are using a rigid Teflon bar that can hold the rebound force of the VA and a length appropriate to generate a free space over the REZ between the pons and the cerebellar flocculus. In this video, we demonstrate our bridge technique for VA-related HFS and discuss the advantages and disadvantages of this novel approach.

Coexistence of neurovascular compression syndrome and unruptured cerebral aneurysm

Unruptured cerebral aneurysms (UCAs) are usually asymptomatic and detected incidentally by intracranial examinations. The coexistence of neurovascular compression syndrome (NVCS) and UCAs has not been well described. The aim of this study was to clarify the characteristics of UCAs with the NVCS. A total of 103 cases that underwent microvascular decompression (MVD) for trigeminal neuralgia (TN) or hemifacial spasm (HFS) were assigned to the NVCS group. The prevalence of UCAs in the NVCS group was compared retrospectively to that in 110 control cases (a control group) by neuro-imaging. Overall treatment courses for NVCS and UCAs were investigated in the NVCS group. Sixteen (15.3%; TN 11 cases, HFS 5 cases) of 103 MVD cases had 19 UCAs, a significantly higher prevalence than the 3.6% in the control group. Binomial logistic regression showed that NVCS is a significant factor for predicting the presence of UCAs, with an odds ratio of 4.80. In the NVCS group, 18 UCAs (94.7%) were supratentorial aneurysms, and 17 UCAs (89.5%) were less than 5 mm in size. Nine UCAs were surgically treated with clipping or coiling. Of the surgical cases, 2 UCAs were treated before MVD for NVCS, whereas the other 7 UCAs were treated after MVD. No aneurysms ruptured during the treatment course. The NVCS occurred with UCAs at a significantly higher rate than in the control group. Most UCAs with the NVCS were supratentorial, small aneurysms that did not affect the surgical treatment of NVCS.

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.

Microvascular decompression for hemifacial spasm involving the vertebral artery

Objective

Microvascular decompression (MVD) has become an accepted treatment modality for the vertebral artery (VA)–involved hemifacial spasm (HFS). The aim of this retrospective study was to evaluate clinical and surgical outcomes of HFS patients undergoing MVD and surgical and cranial nerve complications and investigate reasonable transposition procedures for two different anatomic variations of VA.

Methods

Between January and December 2018, 109 patients underwent first MVD for HFS involving VA at Nanjing Drum Tower Hospital. Based on whether the VA could be moved ventrally at the lower cranial nerves (LCNs) level, patients were assigned to Group A (movable VA, n = 72) or B (unmovable VA, n = 37), and clinical and surgical outcomes and complications on the day of post-surgery and during follow-up were assessed. All patients were followed up ranging from 17 to 24 months with a mean follow-up period of 21 months.

Results

After a mean follow-up of 21 months, the total cure rate significantly decreased in all patients compared to that achieved on the day of surgery, and Group A patients exhibited a higher cure rate versus Group B (93.1% vs. 75.7%, P = 0.015). Group B patients with unmovable VA revealed both higher incidence of surgical complications (45.9% vs. 15.3%, P = 0.001) and frequency of bilateral VA compression (27% vs. 8.3%, P = 0.009) versus Group A. No significant difference was observed in long-term cranial nerve complications.

Conclusions

VA-involved HFS can benefit from MVD strategies after preoperative assessment of VA compression. HFS patients with movable VA may receive better long-term efficacy and fewer complications. A Teflon bridge wedged between the distal VA and medulla gives rise to adequate space for decompression surgery.

Bridge technique for hemifacial spasm with vertebral artery involvement

BACKGROUND

To assess efficacy and safety of a newly developed decompression technique in microvascular decompression for hemifacial spasm (HFS) with vertebral artery (VA) involvement.

METHODS

A rigid Teflon (Bard^® PTFE Felt Pledget, USA) with the ends placed between the lower pons and the flocculus creates a free space over the root exit zone (REZ) of the facial nerve (bridge technique). The bridge technique and the conventional sling technique for VA-related neurovascular compression were compared retrospectively in 60 patients. Elapsed time for decompression, number of Teflon pieces used during the procedure, and incidences of intraoperative manipulation to the lower cranial nerves were investigated. Postoperative outcomes and complications were retrospectively compared in both techniques.

RESULTS

The time from recognition of the REZ to completion of the decompression maneuvers was significantly shorter, and fewer Teflon pieces were required in the bridge technique than in the sling technique. Lower cranial nerve manipulations were performed less in the bridge technique. Although statistical analyses revealed no significant differences in surgical outcomes except spasm-free at postoperative 1 month, the bridge technique is confirmed to provide spasm-free outcomes in the long-term without notable complications.

CONCLUSIONS

The bridge technique is a safe and effective decompression method for VA-involved HFS.

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.

Endoscopic Microvascular Decompression for Hemifacial Spasm

Introduction and Objective

Hemifacial spasm (HFS) is a condition, characterized by painless, involuntary unilateral tonic or clonic contractions of the facial muscles innervated by the ipsilateral facial nerve. HFS starts with contractions in the orbicularis oculi muscle with subsequent eyelid closure and/or eyebrow elevation, but may spread to involve muscles of the frontalis, platysma, and orbicularis oris muscles. Microvascular decompression (MVD) is reliable and accepted surgical treatment for HFS. MVD is the standard surgical technique now for HFS treatment with long-term success rates.

Materials and Methods

We performed fully endoscopic MVD technique for 1 patient with HFS (a 83-year-old female) at our institution. HFS was diagnosed based on the clinical history and presentation, a neurologic examination, and additional imaging findings. Respectively, the durations of HFS were 3 years, respectively. The patient had been previously treated with repeated botulinum toxin injections. Preoperative evaluation was done with magnetic resonance imaging; three-dimensional computed tomography fusion images examinations had identified the anterior inferior cerebellar artery (AICA) as the offending vessel in this patient.

Results

The patient with HFS was treated by fully endoscopic MVD technique. The AICA, which had been identified as the offending vessel by preoperative magnetic resonance imaging, was successfully decompressed. No surgery-related complications occurred and had excellent outcomes with the complete resolution of HFS immediately after the operation.

Conclusions

Endoscopic surgery can provide a more panoramic surgical view than conventional microscopic surgery. Fully endoscopic MVD is both safe and effective in the treatment of HFS. This method minimizes the risks of brain retraction and extensive dissection often required for microscopic exposure. Endoscopic MVD is safe and has advantage over microscope in terms of visualization of structure, identification of neurovascular conflict, but it has a learning curve and technically challenging.

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.

Utilization of 3D imaging reconstructions and assessment of symptom-free survival after microvascular decompression of the facial nerve in hemifacial spasm

OBJECTIVE

Hemifacial spasm (HFS), largely caused by neurovascular compression (NVC) of the facial nerve, is a rare condition characterized by paroxysmal, unilateral, involuntary contraction of facial muscles. It has long been suggested that these symptoms are due to compression at the transition zone of the facial nerve. The aim of this study was to examine symptom-free survival and long-term quality of life (QOL) in HFS patients who underwent microvascular decompression (MVD). A secondary aim was to examine the benefit of utilizing fused MRI and MRA post hoc 3D reconstructions to better characterize compression location at the facial nerve root exit zone (fREZ).

METHODS

The authors retrospectively analyzed patients with HFS who underwent MVD at a single institution, combined with a modified HFS-7 telephone questionnaire. Kaplan-Meier analysis was used to determine event-free survival, and the Wilcoxon signed-rank test was used to compare pre- and postoperative HFS-7 scores.

RESULTS

Thirty-five patients underwent MVD for HFS between 2002 and 2018 with subsequent 3D reconstructions of preoperative images. The telephone questionnaire response rate was 71% (25/35). If patients could not be reached by telephone, then the last clinic follow-up date was recorded and any recurrence noted. Twenty-four patients (69%) were symptom free at longest follow-up. The mean length of follow-up was 2.4 years (1 month to 8 years). The mean symptom-free survival time was 44.9 ± 5.8 months, and the average symptom-control survival was 69.1 ± 4.9 months. Four patients (11%) experienced full recurrence. Median HFS-7 scores were reduced by 18 points after surgery (Z = -4.013, p < 0.0001). Three-dimensional reconstructed images demonstrated that NVC most commonly occurred at the attached segment (74%, 26/35) of the facial nerve within the fREZ and least commonly occurred at the traditionally implicated transition zone (6%, 2/35).

CONCLUSIONS

MVD is a safe and effective treatment that significantly improves QOL measures for patients with HFS. The vast majority of patients (31/35, 89%) were symptom free or reported only mild symptoms at longest follow-up. Symptom recurrence, if it occurred, was within the first 2 years of surgery, which has important implications for patient expectations and informed consent. Three-dimensional image reconstruction analysis determined that culprit compression most commonly occurs proximally along the brainstem at the attached segment. The success of this procedure is dependent on recognizing this pattern and decompressing appropriately. Three-dimensional reconstructions were found to provide much clearer characterization of this area than traditional preoperative imaging. Therefore, the authors suggest that use of these reconstructions in the preoperative setting has the potential to help identify appropriate surgical candidates, guide operative planning, and thus improve outcome in patients with HFS.

Change in basilar artery length and bending according to aging and vertebral artery dominance: A longitudinal study

This study aimed to investigate the basilar artery (BA) geometric changes in a longitudinal study. 154 subjects with normal vertebrobasilar arterial systems on magnetic resonance angiography were assigned into two groups: 1) non-dominant vertebral artery (VA) and 2) VA dominance. We defined the dominant VA as either that the VA is 3 millimeters larger in diameter or the VA is connected to BA in a more straight angle. BA imaging was segmented to obtain BA bending length (BABL) and BA length (BAL). A mixed model ANOVA was conducted to investigate the impact of aging and VA dominance on the change of BABL and BAL after 123.6 ± 16.2 months. There was a significant main effect of VA dominance on the change of BABL after about 10 years, F (1,152) = 39.78, p < 0.01. On the other hand, there was a significant main effect of aging on the change of BAL during the same period of time, F (1,152) = 6.64, p = 0.01. Most subjects had an opposite directional relationship between the dominant VA and BA bending (71.3%; p < 0.01). Our study supported the hypothesis that the bending of the BA depends on the dominance of the VA, whereas the increased length of the BA depends on aging.

The efficacy of temporary clamping of V3 with a suboccipital far-lateral approach in microvascular decompression for Hemifacial spasm associated with the vertebral artery

Hemifacial spasm (HFS) is often caused by compression of the vertebral artery (VA) directly or indirectly as a result of other intervening vessels, so VA-associated HFS is difficult to treat. Recently, we have achieved good surgical outcomes using a far lateral approach and temporary clamping of V3 for VA-associated HFS. Herein, we present our method with an accompanying surgical video. From April 2018 to March 2019, 5 patients with VA-associated HFS underwent surgery, and pre-and postoperative symptoms and postoperative complications were evaluated. In the procedure, the suboccipital muscles were dissected and reflected layer by layer, and the extracranial VA (V3) was secured within the suboccipital triangle. A lateral suboccipital craniotomy followed by far lateral drilling was made to widen the surgical field from the caudolateral side. After reducing the VA flow pressure by temporary clamping of V3, the VA was transposed using a Teflon sling via two triangular space above and below the lower cranial nerves (LCNs). Causative vessels included direct VA compression in two cases and intervening vessels in three cases. The symptoms disappeared in four cases and improved satisfactorily in one case. One patient had mild hearing loss (approximately 10 dB) and hoarseness, but both improved 9 months after surgery. There was no postoperative cerebrospinal fluid leakage in any cases. A wide surgical field via the far lateral approach and the temporary clamping of V3 contributed to thorough observation of the REZ and safe and complete VA transposition.

Anatomical Variations of Vertebrobasilar Artery are Closely Related to the Occurrence of Vertebral Artery Dissection-An MR Angiography Study

GOAL

Intracranial arterial dissection is a major cause of ischemic stroke and subarachnoid hemorrhage in relatively young patients. We assessed the hypothesis that the tortuosity of the vertebrobasilar artery is associated with the occurrence of vertebral artery (VA) dissection, using MR angiography (MRA).

MATERIALS AND METHODS

This study enrolled 43 patients with VA dissection, and 63 age- and sex-matched healthy subjects were used as the controls. MRA was employed to evaluate the presence of dominant VA and the lateral shift of vertebrobasilar junction in both groups. The VA diameters were considered different when the difference was greater than .3 mm. These anatomical variations were divided into 3 types: Type 1 (vertebrobasilar junction within 2 mm from the midline), Type 2 (>2 mm-lateral shift of vertebrobasilar junction to the ipsilateral side of the dominant VA), and Type 3 (>2 mm-lateral shift of vertebrobasilar junction to the contralateral side of the dominant VA).

FINDINGS

The presence of dominant VA and the lateral shift of vertebrobasilar junction were more prevalent in patients with VA dissection than in the controls (OR: 3.46, P = .013, and OR: 4.51, P = .001, respectively). The lateral shift of vertebrobasilar junction was classified into Type 1 (n = 6), Type 2 (n = 13), and Type 3 (n = 17) among patients with VA dissection, while into Type 1 (n = 20), Type 2 (n = 8), and Type 3 (n = 7) among the controls. Type 3 predominance was observed in patients with VA dissection (P = .02).

CONCLUSIONS

Anatomical variations of the vertebrobasilar artery may play an important role in the occurrence of VA dissection.

Anatomic Variation and Hemodynamic Evolution of Vertebrobasilar Arterial System May Contribute to the Development of Vascular Compression in Hemifacial Spasm

BACKGROUND

Hemifacial spasm (HFS) is caused by vascular compression of the facial nerve. The definitive mechanism of offending vessel formation remains unclear. The aim of this study was to explore whether the anatomic and hemodynamic characteristics of the vertebrobasilar artery play a role in problematic vessel formation in HFS.

METHODS

Imaging data of 341 patients with HFS who underwent microvascular decompression were reviewed retrospectively and compared with 360 control subjects. Hemodynamics of typical anatomic variations of the vertebral artery (VA) were analyzed using computational fluid dynamics software.

RESULTS

Asymmetry of the left and right VAs was prevalent, and the left VA was the most dominant VA. A dominant VA was more prevalent in the HFS group than in the control group (P = 0.026). Left HFS had a significantly higher proportion of a left dominant VA, and right HFS had a significantly higher proportion of a right dominant VA (P < 0.001). Computational fluid dynamics models showed that angulation and tortuosity of vessels caused remarkable pressure difference between vascular walls of opposite sides. Dynamic clinical observations showed the mode of vessel transposition coincided with biomechanical characteristics.

CONCLUSIONS

Anatomic variations and hemodynamics of the vertebrobasilar arterial system are likely to contribute to vascular compression formation in HFS.

Vascular tortuosity in relationship with hypertension and posterior fossa volume in hemifacial spasm

Background

Hemifacial spasm (HFS) is a disabling neurological condition. Vascular tortuosity in HFS patients has not been quantified objectively and its relationship with hypertension and posterior fossa volume (PF) is unknown. In a case control magnetic resonance imaging and angiographic (MRI/A) study, we quantified and compared the vascular tortuosity in HFS and controls, and evaluated its relationship with hypertension and PF.

Methods

Using a commercially available vessel probe tool, an index of tortuosity based on vessel over chord length was employed to quantify vascular tortuosity of the vertebral (VA) and basilar arteries (BA) in 79 subjects (40 HFS, 39 controls).

Results

The tortuosity index of the BA (1.09 vs 1.16, p = 0.26, 95 % CI 1.07, 1.23), RVA (1.15 vs 1.15, p = 0.83, 95 % CI 1.06, 1.38) and LVA (1.14 vs 1.288, p = 0.16, 95 % CI 1.14, 1.44) was not different between HFS and controls, with adjustments for PF volume and hypertension.

Conclusions

Contrary to popular belief, our study showed that taking into account hypertension and PF volume, vascular tortuosity of the vertebrobasilar arteries is unlikely to be a major etiologic factor in HFS, though its role in select individuals cannot be excluded. The complex interplay of facial nerve hyperexcitability, genetic predisposition, vascular tortuosity, posterior fossa volume and hypertension needs to be further evaluated.

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.

Revisiting the link between hypertension and hemifacial spasm

The relationship between hypertension and hemifacial spasm (HFS) has been debated. Microvascular decompression surgery is effective in some HFS patients with uncontrolled hypertension. To address current gaps in knowledge, we conducted a meta-analysis of case-control studies that have examined the prevalence of hypertension in HFS patients compared to non-HFS controls. We also evaluated the implications and limitations of the pooled studies. We identified 62 studies from PubMed, The Cochrane Library, Web of Science and Scholar.google.com and six studies that fit our inclusion criteria were included. A random-effects model was used to derive the pooled estimate of the Odds Ratio. The data was plotted on a Forest plot. A pooled analysis involving 51585 subjects, 549 cases, 720 neurological controls and 50316 controls from the general population, showed that HFS patients had a higher chance of developing hypertension (OR = 1.72, 95% CI = (1.12, 2.31), p-value  <0.001). The prevalence of hypertension was higher in HFS patients as compared to non-HFS patients. This meta-analysis highlights a positive correlation between hypertension and HFS. Blood pressure should be closely monitored during the follow-up of HFS patients. Preliminary links between ventrolateral medullary (VLM) compression and HFS should be further evaluated in future studies.