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

Role of a Tortuous Vertebrobasilar Artery and Anchoring Perforators in the Etiology of Hemifacial Spasm

BACKGROUND

In >70% of patients with hemifacial spasm (HFS), the offending artery is either the anterior inferior cerebellar artery (AICA) or posterior inferior cerebellar artery (PICA), without a tortuous vertebrobasilar artery (VBA). We hypothesized that anchoring perforators around the root exit zone (REZ) of the AICA or PICA might induce vascular deviation and compression. We investigated the occurrence of these perforators from the AICA or PICA and the extent of VBA tortuosity to reveal the pathology of vascular compression.

METHODS

This retrospective review included 110 patients after excluding those with vertebral artery (VA) compression alone. The occurrence of perforators was determined according to operative findings within 5 mm of the REZ, and VBA tortuosity was evaluated using MATLAB. We analyzed the association between perforators, VBA tortuosity, and the surgical implications.

RESULTS

The occurrence of perforators from the offending AICA or PICA around the REZ was significantly higher in the group without VA compression (Group A) than in the group with VA compression (Group B). VBA tortuosity was significantly lower in Group A. VBA tortuosity was inversely correlated with the presence of AICA or PICA perforators in all 110 patients. Operative results were similar between the groups, although patients with low VBA tortuosity tended to require interposition in decompression procedures.

CONCLUSIONS

Anchoring perforators around the REZ play a crucial role in vascular compression for patients with less tortuous VBAs. Moreover, surgeons should be prepared to deal with multiple perforators in a more complicated surgery in cases of less tortuous VBA.

MRI measurements the linear volume of posterior cranial fossa in patients with hemifacial spasm

To explore the pathogenesis of hemifacial spasm (HFS) and the effect of posterior fossa volume on postoperative complications. The measurements of the antero-posterior diameter of foramen magnum, the length of supraocciput, the angle of tentorium cerebelli, clivus and occipital bone were performed on MRI. The data of measurements and postoperative complications were then analyzed and statistically examined. The antero-posterior diameter of the foramen magnum was smaller in HFS group (34.98 ± 2.83) mm than in control group (35.83 ± 2.67) mm (P < 0.05); The length of supraocciput was smaller in HFS group (44.67 ± 4.48) mm than in control group (45.84 ± 4.25) mm (P < 0.05); The angle of tentorium cerebelli was larger in HFS group (41.03 ± 5.01)°than in control group (37.28 ± 4.31)° (P < 0.05); The angle of clivus was smaller in HFS group (52.71 ± 6.22)° than in control group (56.39 ± 6.61)° (P < 0.05). The operation time was significantly longer in crowding group (107.90 ± 26.20) min than in non-crowding group (96.48 ± 20.52) min (P < 0.05); The incidence of postoperative facial paralysis was significantly higher in crowding group (16.19%) than in non-crowding group (7.20%) (P < 0.05); The incidence of postoperative hearing loss was significantly higher in crowding group (13.33%) than in non-crowding group (4.00%) (P < 0.05). Factors such as shorter antero-posterior diameter of foramen magnum, lower tentorium cerebelli, and shorter length of supraocciput in patients with HFS indicate the posterior fossa dysplasia and promote the occurrence of HFS. The crowding of the posterior fossa will increase the difficulty of the surgery and the incidence of postoperative facial paralysis and hearing loss.

[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.

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.

Treatment of Blepharospasm/Hemifacial Spasm

OPINION STATEMENT

The treatment of both hemifacial spasm (HFS) and blepharospasm (BEB) requires making the appropriate clinical diagnosis. Advance imaging and electrophysiologic studies are useful; however, one's clinical suspicion is paramount. The purpose of this review is to summarize current and emerging therapies for both entities. Botulinum toxin (BTX) remains the first-line therapy to treat both conditions. If chemodenervation has failed, surgery may be considered. Due to the risks associated with surgery, the benefits of this option must be carefully weighed. Better surgical outcomes are possible when procedures are performed at tertiary centers with experienced surgeons and advanced imaging techniques. Microvascular decompression is an efficacious method to treat HFS, and myectomy is an option for medication-refractory BEB; the risks of the latter may outweigh any meaningful clinical benefits. Oral agents only provide short-term relief and can cause several unwanted effects; they are reserved for patients who cannot receive BTX and/or surgery. Transcranial magnetic stimulation has gained some traction in the treatment of BEB and may provide safer non-invasive options for refractory patients in the future.