Angiographic manifestations and operative findings with 70 cases of hemifacial spasm: relation of common trunk anomalies

Is Common Trunk Anomaly Frequent in Hemifacial Spasm? Comparison with Normal Subjects Using Magnetic Resonance Imaging

OBJECTIVE

Hemifacial spasm (HFS) results from vascular compression at the root exit of the facial nerve. Although the underlying etiology has yet to be identified, it has been suggested that congenital vascular anomalies are involved. We have hypothesized common trunk anomaly of the anterior inferior cerebellar artery (AICA) and posterior inferior cerebellar artery (PICA) which may play a role in HFS. However, no previous studies have directly compared the incidence of this anomaly between HFS patients and normal subjects. The present study was designed to address this gap in the literature.

METHODS

This case-control study compared magnetic resonance angiography data from 65 HFS patients and 65 normal subjects. Dominant AICA/PICA is defined as the absence of PICA/AICA, with the remaining AICA/PICA supplying both vascular territories. The term "common trunk" encompasses both dominant AICA and dominant PICA. The frequency of common trunk and dominant AICA/PICA was compared between the 2 groups.

RESULTS

There were no significant differences in the incidence of a common trunk (68.5% and 64.6%), dominant AICA (30.8% and 32.3%) and dominant PICA (37.7% and 32.3%) between the 2 groups. Additionally, no differences were found in the frequency of atherosclerosis risk factors.

CONCLUSIONS

There was no apparent association between common trunk anomaly and HFS. It is suspected that some vascular anomalies other than a common trunk are involved in HFS.

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.

Common trunk anomaly of the anterior and posterior inferior cerebellar artery in hemifacial spasm

BACKGROUND

The common trunk anomaly of the anterior and posterior inferior cerebellar artery (APC) is a variant artery that causes a hemifacial spasm (HFS). The anatomical characteristics include a large diameter of the trunk and the existence of the bifurcation near the facial nerve root entry zone (REZ). Despite APC being encountered at a constant rate in microvascular decompression (MVD), the anatomical and technical issues of transposing APC have not been entirely focused on yet.

METHODS

We reviewed our 68 cases with APC involvement. Patient background, radiological findings, and operative video recordings were reviewed retrospectively. The location of the bifurcation of APC and the distribution of perforators were investigated. Surgical outcomes were assessed in the long term.

RESULTS

APC involvement was diagnosed preoperatively in all cases by careful observation with MRI. Three-dimensional images determined the anatomical characteristics of APC and depicted the relationship with the facial nerve. All patients had a bifurcation close to the root entry zone that was required to transpose, including the common trunk and the distal branches, to achieve sufficient decompression. While adequate transposition from the REZ was accomplished in most cases, it was difficult to complete transposition due to short perforators in 6 patients (8.8%), resulting in interposition. Fifty-three patients (77.9%) became spasm free immediately after surgery, 66 patients (97.1%) were after 6 months, and all patients (100%) became spasm free within a year. Spasm-free status was maintained during the follow-up period (4.7 years) in all patients except one in whom facial spasm recurred 2 years after the initial surgery.

CONCLUSIONS

Transposing the common trunk with the bifurcation and distal branches contributes to obtaining favorable surgical outcomes in APC-related HFS.

Veins of the Cerebellopontine Angle and Specific Complications of Sacrifice, with Special Emphasis on Microvascular Decompression Surgery. A Review

Good knowledge of the anatomy of veins is of crucial importance for the functional surgery of cranial nerve (CN) disorders, especially microvascular decompression for trigeminal neuralgia (TN), hemifacial spasm (HFS), and vagoglossopharyngeal neuralgia (VGPN). Although controversial, veins may be involved in neurovascular conflicts and may constitute dangerous obstacles to access to the CNs. With the aim of estimating the implications of veins in those diseases and evaluating the linked surgical difficulties, we carried out a review of the literature from 2000 to the end of February 2018. For this review, articles found on PubMed that gave enough precision about veins were retained (39 articles on TN, 38 on HFS, 8 on VGPN, and 26 on complications related to venous sacrifices). Before this review, we described a simplified anatomic classification of veins, amenable to easing the surgical approach to CNs. Access to the trigeminal nerve, via the infratentorial-supracerebellar route, is almost always affected by the superficial superior petrosal venous system, whereas access to the facial and cochleovestibular complex as well as to the lower CNs, through the infrafloccular trajectory, is almost always exempt of important venous obstacles. Respective incidences of venous compression at the origin of hyperactive CN syndromes are given. The percentages of a venous conflict alone were calculated at 10.8% for TN, 0.1% for HFS, and 2.9% for VGPN. We review the complications considered in relation with venous sacrifices. Precautions to minimize these complications are given.

Microvascular Decompression for Patients With Hemifacial Spasm Associated With Common Trunk Anomaly of the Cerebellar Arteries-Case Study and Review of Literature

BACKGROUND

Few previous studies have described the origin of both anterior and posterior inferior cerebellar arteries from one vessel as a common trunk anomaly. No previous studies have clearly described the aforementioned anomaly depending on intraoperative endoscopic visualization.

OBJECTIVE

To evaluate the association of a common trunk anomaly with hemifacial spasm, which makes microvascular decompression more challenging.

METHODS

All patients with common trunk anomaly associated with hemifacial spasm who received surgical treatment between 2006 and 2015 in our institution were identified in our prospectively collected database. Detection of the common trunk anomaly was performed using the intraoperative high-definition endoscopic inspection and confirmed by a retrospective review of the obtained operative videos.

RESULTS

Out of 248 cases of hemifacial spasm, 21 cases with a common trunk anomaly were detected, with an incidence rate of 8.5%. In 6 cases, the spasm was caused by more than 1 offending vessel "complex compression." In 19 cases, total recovery occurred on follow-up, while in 1 case, 90% recovery occurred. One patient was spasm-free immediately after surgery, but died 3 wk after operation from herpes encephalitis.

CONCLUSION

Common trunk anomaly in hemifacial spasm is rare. The surgical technique is mostly identical to decompression with normally arising vessels. However, in case of a bifurcation situated close to the compression site where the offending vessel cannot be transposed freely, an extensive cushioning along the trunk and the offending vessels with teflon pledgets should be performed. The presence of a common trunk anomaly does not affect the surgical 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.

Variations of the cerebellar arteries at CT angiography

PURPOSE

There are few studies that investigated variations of the cerebellar arteries, and the prevalence of some variations has not been reported. We aim to identify and evaluate variations of the cerebellar arteries using CTA.

METHODS

The findings in 341 patients who underwent 64-slice CTA were reviewed for anatomical variations of the cerebellar arteries. We assessed variations and classified our findings to describe the results of our analysis. We attempted to create an anatomical model for CTA that is somewhat different from previous studies and described our findings according to vascular anatomy.

RESULTS

Only 11.7% of the 341 patients had all the cerebellar arteries without anatomical variations. Vertebral artery continuation as posterior inferior cerebellar artery (PICA) was found in 4.4% of the patients. Absence of the anterior inferior cerebellar artery (AICA) was observed in 36.1%, and absence of the PICA was observed in 6.7% of the patients. The origin of the PICA was extradural in 71 (20.8%) patients. Double origin of the PICA, PICA duplication, and fenestration were rarely found. Duplication of the AICA (7.9%), and superior cerebellar artery (SCA) (20.5%), and early bifurcation of SCA (9.4%) were frequently observed. Superior cerebellar artery and posterior cerebral artery (PCA) common trunk and SCA originating from PCA were found 9.4 and 8.2%, respectively.

CONCLUSION

Variations of the cerebral arteries can be easily evaluated by CTA. Recognizing and reporting them at cerebral CT angiography may be clinically important.

Hemifacial spasm: neurovascular compressive patterns and surgical significance

BACKGROUND

The aim of this study was to report further investigation of neurovascular compression as a cause of hemifacial spasm (HFS) and to provide useful surgical guidelines by describing the compression patterns.

MATERIAL AND METHODS

From January 2004 to February 2006, 236 consecutive patients with HFS underwent microvascular decompression (MVD) in a single centre. Based on the operation and medical records, the intraoperative findings and post-operative outcomes were obtained and analysed.

RESULTS

We found that 95.3% of lesions had accompanying causative factors that made the neurovascular compression inevitable. Based on the contributing factors, compression patterns were categorised into six different types including: loop (n = 11: 4.6%), arachnoid (n = 66: 27.9%), perforator (n = 58: 24.6%), branch (n = 18: 7.6%), sandwich (n = 28: 11.9%), and tandem (n = 52: 22.0%). The compression patterns were significantly correlated with the compressing vessels involved. Thirty-two (86.5%) of 37 lesions where the vertebral artery was the compressing vessel involved the tandem type. Anterior inferior cerebellar artery was the compressing vessel involved in 49 (84.5%) of 58 perforator type compressions, while posterior inferior cerebellar artery was the compressing vessel involved in 8 (72.7%) of 11 loop type compressions.

CONCLUSIONS

Once the compressing vessel responsible for the neurovascular compression are identified, the probable pattern of compression can be anticipated; this knowledge could facilitate the application of the appropriate operative procedures and minimise post-operative complications.

The anteroinferior cerebellar artery embedded in the subarcuate fossa: a rare anomaly and its clinical significance

OBJECTIVE

The purpose of this study is to call attention to an anomaly in which a segment of the anteroinferior cerebellar artery (AICA) is embedded in the dura or bone surrounding the subarcuate fossa, a small depression in the bone posterior to the internal acoustic meatus (IAM), through which the subarcuate artery enters the bone. This anomaly places the artery at risk in removing the posterior wall of the IAM.

METHODS

An anomalous AICA having a segment that was embedded in the dura covering on the bone surrounding the subarcuate fossa was found during a microsurgical dissection course. The senior author (ALR) has observed this anomaly in four patients during surgery for acoustic neuromas and in three specimens in microsurgery dissection courses. To define the microsurgical anatomy of the anomalous artery further, the latex-injected specimen was dissected in a stepwise manner using x3 to x40 magnification.

RESULTS

The anomalous AICA described in this report bifurcated into a rostral trunk and a caudal trunk near the facial-vestibulocochlear nerve complex. The caudal trunk formed a sharp lateral loop that was embedded in the dura covering the subarcuate fossa. The involved trunk continued to supply the suboccipital area normally supplied by the posteroinferior cerebellar artery, which was hypoplastic. The dura surrounding the anomalous loop was opened, and the adjacent bone was removed to free the anomalous loop from the subarcuate fossa so that the artery could be displaced medially to remove the posterior wall of the IAM. Although it has been reported that the AICA may occasionally be adherent to the dura over the subarcuate fossa, this study is the first to demonstrate an AICA that is embedded in the dura and bone of the subarcuate fossa.

CONCLUSION

Mobilizing the AICA loop that is embedded in the subarcuate fossa posterior to the IAM places the involved AICA at significant risk in exposing the contents of the IAM.