Distal Aneurysms of the Posterior Inferior Cerebellar Artery: The Rare Surgical Lesion

Endovascular treatment of posterior inferior cerebellar artery trunk aneurysm

BACKGROUND

The posterior inferior cerebellar artery (PICA) generally originates from the vertebral artery (VA) and is the most complex cerebellar artery. Aneurysms can occur at any site along the PICA trunk. Although most PICA aneurysms are located at the VA-PICA junction, a small proportion is located at the PICA trunk. Endovascular treatment (EVT) of aneurysms in the PICA trunk may be difficult and complex.

METHODS

We performed a review to expound upon EVT of PICA trunk aneurysms.

RESULTS

The PICA can be divided into five segments (p1-5); the p1-3 segments are proximal segments, and the p4-5 segments are distal segments. Most PICA trunk aneurysms are dissecting aneurysms. Sometimes, the PICA can give rise to flow-related aneurysms in association with cerebellar arteriovenous malformations. Most aneurysms of the PICA trunk require aggressive treatment, especially those that have ruptured. Currently, the EVT mainly includes selective coiling with/without stent assistance and parent artery occlusion. Recently, some new devices, such as flow diversion and Barricade and Kaneka ED coils, can be used to treat PICA trunk aneurysms. The risk of complications with EVT seems to be higher; however, most complications are only transient or mild, and some are even clinically silent. In addition, open surgery is still an important option.

CONCLUSION

For PICA trunk aneurysms, the treatment choice should be assessed on a case-by-case basis. The rate of permanent morbidity of the EVT is low. EVT is an effective method for treating PICA trunk aneurysms.

Safety and efficacy of treatment strategies for posterior inferior cerebellar artery aneurysms: a systematic review and meta-analysis

INTRODUCTION

We conducted a systematic review of the literature to evaluate the safety and efficacy of treatment strategies for PICA aneurysms.

METHODS

A systematic search of Medline, EMBASE, Scopus, and Web of Science was done for studies published through November 2015. We included studies that described treatment of PICA aneurysms with ≥10 patients. Random-effects meta-analysis was used to pool the following outcomes: complete occlusion, technical success, periprocedural morbidity/mortality, stroke rates, aneurysm recurrence/rebleed, CN palsies rates, and long-term neurological morbidity/mortality.

RESULTS

We included 29 studies with 796 PICA aneurysms. When considering all ruptured PICA aneurysms, complete occlusion rates were 97.1 % (95 % CI = 94.5-99.0 %) in the surgical group and 84.3 % (95 % CI = 73.8-92.6 %) in the endovascular group. Aneurysm recurrence occurred in 1.4 % (95 % CI = 0.3-3.3 %) after surgery and in 6.9 % (95 % CI = 3.6-10.9 %) after endovascular treatment. Overall neurological morbidity and mortality were 14.4 % (95 % CI = 8.7-21.2 %) and 9.8 % (95 % CI = 5.8-14.8 %) after surgery and 15.1 % (95 % CI = 10.5-20.2 %) and 17.1 % (95 % CI = 11.5-23.7 %) after endovascular treatment, respectively. When considering all unruptured PICA aneurysms, complete occlusion rates were 92.9 % (95 % CI = 79.5-100 %) in the surgical group and 75.7 % (95 % CI = 45.4-97.1 %) in the endovascular group. Overall long-term good neurological outcome rates were 91.5 % (95 % CI = 74.4-100 %) in the surgical series and 93.3 % (95 % CI = 82.7-99.5 %) in the endovascular group.

CONCLUSIONS

Our meta-analysis demonstrated that both treatment modalities are technically feasible with high rates of technical success and effective with sufficient long-term aneurysm occlusion rates. Our data suggest that surgery is associated with superior angiographic outcomes. While endovascular therapy could be a reasonable first-line treatment option for proximal PICA aneurysms, surgery remains a highly effective first-line choice for distal PICA aneurysms. These findings should be considered when deciding the best therapeutic strategy.

Posterior inferior cerebellar artery reimplantation: buffer lengths, perforator anatomy, and technical limitations

OBJECTIVE

Reimplantation of the posterior inferior cerebellar artery (PICA) to the vertebral artery (VA) is a safe and effective bypass option after deliberate PICA sacrifice during the treatment of nonsaccular and dissecting aneurysms at this location. However, the anatomy and limitations of this technique have not been studied. The goal of this study was to define the surgical anatomy and buffer lengths specific to the proximal segment of the PICA related to 2 variations of PICA reimplantation: 1) reimplantation “along-VA” (simulating a dissecting VA aneurysm), and 2) reimplantation “across-VA” (simulating a nonclippable, proximal PICA aneurysm).

METHODS

Ten cadaver heads (20 sides) were prepared for surgical simulation. Twenty far-lateral approaches were performed. The PICA was mobilized and reimplanted onto the VA according to 2 different paradigms: 1) transposition along the axis of the VA (along-VA) to simulate a dissecting VA, and 2) transposition perpendicular to the axis of the VA (across-VA) to simulate a nonclippable, proximal PICA aneurysm. The buffer lengths provided by mobilization of the artery in each paradigm were measured and the anatomy of perforator branching on the proximal PICAs was analyzed.

RESULTS

The PICA was reimplanted in all surgical simulations. The most common perforating artery on the P1 and P2 segments was the short circumflex type. No direct perforator was found on the P1 segment. The mean buffer length with reimplantation along the VA axis was 13.43 ± 4.61 mm, and it was 6.97 ± 4.04 mm with reimplantation across the VA. The PICA was less maneuverable when it was reimplanted across the VA, due to perforator branches of the PICA (P3 segment).

CONCLUSIONS

The buffer lengths measured in this study describe the limitations of PICA reimplantation as a revascularization procedure for nonsaccular aneurysms in this location. PICA reimplantation is a revascularization option for dissecting VA aneurysms incorporating the PICA origin that are < 13 mm in length, and for nonsaccular proximal PICA aneurysms that are < 6 mm in diameter. The final decision to reimplant the PICA depends on careful inspection of perforator anatomy that is not visible preoperatively on angiography, as well as an assessment of technical difficulty intraoperatively.