Perforating branches from offending arteries in hemifacial spasm: anatomical correlation with vertebrobasilar configuration

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.

Prospective, Multicenter Clinical Study of Microvascular Decompression for Hemifacial Spasm

BACKGROUND

Microvascular decompression (MVD) is the most effective procedure for hemifacial spasm (HFS). MVD results from nonspecialized or low-volume institutes are not always reliable. Most studies on MVD for HFS are retrospective and single centered; to the best of our knowledge, no prospective, multicenter studies exist.

OBJECTIVE

To evaluate short- and long-term outcomes and complications in patients who underwent MVD for HFS in specialized Japanese institutions, in this multicenter, prospective, cohort study.

METHODS

Included patients had undergone MVD for HFS in study centers between April 2012 and March 2015. Patients' postoperative grade of involuntary movements and complications were recorded postoperatively at 7 d (short-term) and at 1 (mid-term) and 3 (long-term) yr.

RESULTS

A total of 486 patients (150 men, 336 women; mean age 53.9 yr with 181 patients over 60 yr) were enrolled during the study period. Neuromonitoring was used in 96.3% of the cases. The complete cure rate of symptom relief, mortality rate, and complication rate at short-term follow-up were 70.6%, 0%, and 15%, respectively. The long-term follow-up was completed by 463 patients (95.3%); the complete cure rate of symptom relief and complication rate were 87.1% and 3.0%, respectively.

CONCLUSION

Our study revealed that under expert guidance and intraoperative neuromonitoring, the long-term curative effect rate of MVD for HFS is high, while complications are uncommon and usually transient. Our results indicate that MVD is an effective and safe treatment for patients with HFS, including elderly patients.

Surgical anatomy for hemifacial spasm

Classically in the cerebello-pontine angle the facial (CN VII) and vestibular-cochlear (CN VIII) nerves should run parallel with the anterior inferior cerebellar artery, whereas the lower nerves (CN IX-XI) continue with the posterior-inferior-cerebellar artery (PICA). In fact, this is not always true, particularly when dealing with hemispasm surgery where the relationships between CN VII, CN VIII and PICA are often different and closer. Knowledge of anatomical bases in surgical situation will help neurosurgeons to appreciate anatomical nuances, that are important to increase effectiveness and safety of hemifacial spasm surgery.

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.

A Perforating Artery Compressing the Nerve Rootlet and Causing Glossopharyngeal Neuralgia

BACKGROUND

A surgical procedure for glossopharyngeal neuralgia (GPN) was selected from microvascular decompression, glossopharyngeal and upper vagal rhizotomy, or a combination of these procedures based on the presence of arteries compressing the glossopharyngeal and vagal rootlets. The offending artery is usually a main trunk or branch of the cerebellar arteries. A perforating artery is a known but uncommon variation of the offending artery that causes GPN. The appropriate procedure for such cases is unknown.

OBJECTIVE

To analyze the clinical significance of the perforating artery in GPN, we describe 2 patients with a perforating artery compressing the rootlet, and its mobilization relieved neuralgia. We examined the validity of decompressing a perforating artery as an alternative to rhizotomy in such cases.

METHODS

We independently reviewed 12 GPN patients treated with microvascular decompression. The patients' pain severity, medication doses, preoperative imaging studies, intraoperative findings, and outcomes were examined.

RESULTS

Eleven patients had neurovascular compression of the glossopharyngeal nerve. In 2 of the patients, a perforating artery compressed the rootlet, thereby generating an indentation and creating a discoloration of the rootlet. Mobilizing the perforating artery with no additional rhizotomy provided complete pain relief with no significant complications and allowed the discontinuation of medications.

CONCLUSION

Even a small perforating artery can cause GPN when it compresses the rootlet. In such cases, mobilization of the perforating artery with no additional rhizotomy is an effective surgical option.

Microvascular anatomy of the cerebellar parafloccular perforating space

OBJECT

The cerebellopontine angle is a common site for tumor growth and vascular pathologies requiring surgical manipulations that jeopardize cranial nerve integrity and cerebellar and brainstem perfusion. To date, a detailed study of vessels perforating the cisternal surface of the middle cerebellar peduncle—namely, the paraflocculus or parafloccular perforating space—has yet to be published. In this report, the perforating vessels of the anterior inferior cerebellar artery (AICA) in the parafloccular space, or on the cisternal surface of the middle cerebellar peduncle, are described to elucidate their relevance pertaining to microsurgery and the different pathologies that occur at the cerebellopontine angle.

METHODS

Fourteen cadaveric cerebellopontine cisterns (CPCs) were studied. Anatomical dissections and analysis of the perforating arteries of the AICA and posterior inferior cerebellar artery at the parafloccular space were recorded using direct visualization by surgical microscope, optical histology, and scanning electron microscope. A comprehensive review of the English-language and Spanish-language literature was also performed, and findings related to anatomy, histology, physiology, neurology, neuroradiology, microsurgery, and endovascular surgery pertaining to the cerebellar flocculus or parafloccular spaces are summarized.

RESULTS

A total of 298 perforating arteries were found in the dissected specimens, with a minimum of 15 to a maximum of 26 vessels per parafloccular perforating space. The average outer diameter of the cisternal portion of the perforating arteries was 0.11 ± 0.042 mm (mean ± SD) and the average length was 2.84 ± 1.2 mm. Detailed schematics and the surgical anatomy of the perforating vessels at the CPC and their clinical relevance are reported.

CONCLUSIONS

The parafloccular space is a key entry point for many perforating vessels toward the middle cerebellar peduncle and lateral brainstem, and it must be respected and protected during surgical approaches to the cerebellopontine angle.

Microvascular decompression for hemifacial spasm associated with vertebrobasilar artery

OBJECTIVE

Hemifacial spasm (HFS) is considered as a reversible pathophysiological condition mainly induced by continuous vascular compression of the facial nerve root exit zone (REZ) at the cerebellopontine angle. As an offending vessel, vertebrobasilar artery tends to compress much more heavily than others. The authors analyzed HFS caused by vertebrobasilar artery and described the relationships between microsurgical findings and clinical courses.

METHODS

Out of 1,798 cases treated with microvascular decompression (MVD) from Jan. 1980 to Dec. 2004, the causative vessels were either vertebral artery or basilar artery in 87 patients. Seventy-nine patients were enrolled in this study. Preoperatively, computed tomography (CT) or brain magnetic resonance (MR) imaging with 3-dimentional short range MR technique was performed and CT was checked immediately or 2-3 days after anesthetic recovery. The authors retrospectively analyzed the clinical features, the compression patterns of the vessels at the time of surgery and treatment outcomes.

RESULTS

There were 47 were male and 32 female patients. HFS developed on the left side in 52 cases and on the right side in 27. The mean age of onset was 52.3 years (range 19-60) and the mean duration of symptoms was 10.7 years. Many patients (39 cases; 49.1%) had past history of hypertension. HFS caused only by the vertebral artery was 8 cases although most of the other cases were caused by vertebral artery (VA) in combination with its branching arteries. Most frequently, the VA and the posterior inferior cerebellar artery (PICA) were the simultaneous causative blood vessels comprising 32 cases (40.5%), and in 27 cases (34.2%) the VA and the anterior inferior cerebellar artery (AICA) were the offenders. Facial symptoms disappeared in 61 cases (77.2%) immediately after the operation and 68 cases (86.1%) showed good outcome after 6 months. Surgical outcome just after the operation was poor in whom the perforators arose from the offending vessels concurrently (p<0.05).

CONCLUSION

In case where the vertebral artery is a cause of HFS, commonly branching arteries associated with main arterial compression on facial REZ requires more definite treatment for proper decompression because of its relatively poor results compared to the condition caused by other vascular compressive origins.