Blind-Alley Formation and Occipital Artery-Posterior Inferior Cerebellar Artery Bypass for the Treatment of Unclippable Vertebral Artery Aneurysms with Posterior Inferior Cerebellar Artery Involvement

Posterior Inferior Cerebellar Artery-Posterior Inferior Cerebellar Artery Bypass versus Occipital Artery-Posterior Inferior Cerebellar Artery Bypass for Treating Posterior Circulation Aneurysms: A Systematic Review and Comparative Meta-Analysis

BACKGROUND

When traditional therapies are unsuitable, revascularization becomes essential for managing posterior inferior cerebellar artery (PICA) or vertebral artery aneurysms. Notably, the PICA-PICA bypass has emerged as a promising option, overshadowing the occipital artery-PICA (OA-PICA) bypass. The objective was to compare the safety and efficacy of OA-PICA and PICA-PICA bypasses.

METHODS

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines, we conducted a systematic review and meta-analysis to evaluate the safety and efficacy of OA-PICA and PICA-PICA bypasses for treating posterior circulation aneurysms.

RESULTS

We analyzed 13 studies for the PICA-PICA bypass and 16 studies on the OA-PICA bypass, involving 84 and 110 patients, respectively. The median average follow-up for PICA-PICA bypass was 8 months (2-50.3 months), while for OA-PICA, it was 27.8 months (6-84 months). The patency rate for OA-PICA was 97% (95% confidence interval [CI]: 92%-100%) and 100% (95% CI: 95%-100%) for PICA-PICA. Complication rates were 29% (95% CI: 10%-47%) for OA-PICA and 12% (95% CI: 3%-21%) for PICA-PICA. Good clinical outcomes were observed in 71% (95% CI: 52%-90%) of OA-PICA patients and 87% (95% CI: 75%-100%) of PICA-PICA patients. Procedure-related mortality was 1% (95% CI: 0%-6%) for OA-PICA and 1% (95% CI: 0%-10%) for PICA-PICA.

CONCLUSIONS

Both procedures have demonstrated promising results in efficacy and safety. PICA-PICA exhibits slightly better patency rates, better clinical outcomes, and fewer complications, but with a lack of substantial follow-up and a smaller sample size. The choice between these procedures should be based on the surgeon's expertise and the patient's anatomy.

Cerebral revascularization for complex vertebrobasilar artery dissecting aneurysms

Vertebrobasilar artery dissecting aneurysms (VBDAs) are the most surgically challenging type of aneurysm. Cerebral revascularization is the ultimate treatment for complex VBDAs. We retrospectively analysed the characteristics, surgical outcomes and follow-up data of 21 patients who underwent cerebral revascularization to treat complex VBDAs from 2015 to 2022. According to the location of the aneurysm and the anatomic relationship between the VBDA and the PICA, VBDA patients were classified into four groups: aneurysms located at the VA with PICA involvement (10 patients), aneurysms located at the VA without PICA involvement (1 patient), aneurysms located at the basilar apex segment (1 patient) and aneurysms located at the basilar trunk segment (9 patients). A surgical algorithm for complex VBDAs was determined primarily by the location of the aneurysm, the status of the aneurysm and the ability of retrograde blood flow to reach the proximal vertebrobasilar artery. Surgical modalities for patients with aneurysms in the VA with PICA involvement included low-flow (OA-PICA) bypasses with aneurysm trapping, aneurysm excision or reconstructive clip in 8 patients and STA-PCA bypass combined with PICA preservation and aneurysm trapping in 2 patients. In patients with aneurysms in the VA without PICA involvement, aneurysm excision was performed without cerebral bypass. In patients with aneurysms in the basilar apex segment, high-flow bypass (ECA-RA-P2) with aneurysm trapping was performed. In patients with aneurysms in the basilar trunk segment, surgical modalities included high-flow bypasses (ECA-RA-P2 and LVA-RA-P2) with aneurysm trapping or proximal occlusion in 6 patients, ECA-RA-P2 bypass with partial proximal occlusion in 1 patient, ECA-RA-P2 bypass alone in 1 patient, and STA-PCA bypass with R-VA narrowing in 1 patient. Of the 21 patients, 20 experienced clinical improvement or no change, and 17 of 21 patients achieved favourable functional outcomes (mRS ≤ 2). However, one patient died of infarction and respiratory failure postoperatively. Aneurysms were completely obliterated in 13 patients, shrank in 5 patients and stabilized in 2 patients. The median follow-up period was 32.5 months. During the follow-up period, all bypasses were patent, and further clinical improvement was observed in 11 patients. Cerebral revascularization appears to be safe and effective for the treatment of complex VBDAs, and cerebral revascularization could act as a complementary treatment strategy.

Microsurgical partial trapping for the treatment of unclippable vertebral artery aneurysms: Experience from 27 patients and review of literature

BACKGROUND

The efficacy and safety of partial trapping for the treatment of unclippable vertebral artery aneurysms (UVAs) are still questionable. The partial trapping method (proximal or distal occlusion) was used in the treatment of aneurysms to simplify the surgical procedure and avoid postoperative complications.

METHODS

This study included 27 patients with UVAs who underwent microsurgical partial trapping between January 2015 and August 2022, and their postoperative outcomes and complications were retrospectively reviewed and evaluated.

RESULTS

Ruptured UVAs were detected in 25 (92.6%) patients, and 13 (48.1%) patients had poor-grade status. Fusiform dissection, dissecting, and fusiform aneurysms were observed in 17 (63%), 7 (25.9%), and 3 (11.1%) patients, respectively. By location, preposterior inferior cerebellar artery (PICA), PICA, post- PICA, and non-PICA types were noted in 7 (25.9%), 9 (33.3%), 6 (22.2%), and 5 (18.5%) patients, respectively. Microsurgical partial trapping was performed in all patients (blind-alley formation in 96.3%). Complete aneurysm obliteration was achieved in 26 (96.3%) patients. Immediate complete obliteration was achieved in 21 (77.8%) patients, delayed thrombosis within 7 days in 5 (18.5%), and nearly complete obliteration in 1 (3.7%). No re-bleeding was detected in all patients. Favorable outcomes 3 months after the operation were achieved by 92.9% of the patients in the good-grade group and 85.2% overall.

CONCLUSIONS

Microsurgical partial trapping, especially the blind-alley formation technique, was a safe and effective treatment of UVAs with high rates of aneurysm thrombosis. The appropriate sites for clip occlusion were dependent on the angioarchitecture of UVAs.

Efficacy and predicting factors of multimodal treatment for ruptured intracranial vertebral artery dissecting aneurysms

We aimed to investigate the efficacy of our multimodal strategies and propose a treatment algorithm for ruptured vertebral artery dissecting aneurysms (VADAs). This study included 41 patients treated at a single institution between 2015 and 2022. The treatment modalities were justified based on the collateral circulation and aneurysm location related to the posterior inferior cerebellar artery (PICA). Treatment outcomes and complications of each treatment group were analyzed. The association between the collateral blood flow and the postoperative vertebrobasilar ischemia (VBI) was also investigated. There were 17 post-PICA, 10 PICA-involved, 7 pre-PICA, and 7 non-PICA types. Reconstruction techniques included flow diversion devices (n = 11) and stent-assisted coiling (n = 3). Deconstruction techniques included coil trapping (n=17) and microsurgical parent artery occlusion with (n = 8) or without PICA revascularization (n = 2). Five (18.5%) of the deconstruction group had postoperative VBI. Overall favorable outcomes in both groups were observed in 70.7% of patients with a mean follow-up time of 21.5 months. Poor World Federation of Neurosurgical Societies grade (IV-V) was identified as a predictor of unfavorable outcomes (p = 0.003). In addition, the VA4/BA4 ratio > 0.22, the presence of collateral blood flow from the posterior communicating artery (PcomA), and a contralateral VA diameter > 2.5 mm were associated with a lower risk of postoperative VBI. In summary, the proposed strategic treatment in this study is pragmatic, yielding satisfactory results where a deconstructive technique should be used with caution, particularly when there is a flow mismatch or the absence of collateral PcomA in the vertebrobasilar circulation.

Far-lateral approach without C1 laminectomy for microsurgical treatment of vertebral artery and proximal posterior inferior cerebellar artery aneurysms: Experience from 48 patients

Background

In the endovascular era, most of vertebral artery (VA) and posterior inferior cerebellar artery (PICA) aneurysms were mainly treated with endovascular procedures. This study aimed to demonstrate the microsurgical treatment via the far-lateral approach without C1 laminectomy and its clinical outcomes.

Methods

Forty-eight patients with VA and proximal PICA aneurysms treated by microsurgery through the far-lateral approach without C1 laminectomy, between January 2016 and June 2021, were retrospectively evaluated.

Results

Most patients (87.5%) presented with subarachnoid hemorrhage. Grading at presentation was poor in 41.7%. The rates of VA dissecting aneurysms, saccular aneurysms of the VA-PICA junction, and true PICA saccular aneurysms were 54.2, 18.7, and 14.6%, respectively. All aneurysms were located above the lower margin of the foramen magnum. The far-lateral approach without C1 laminectomy was successfully used in all patients without residual aneurysms. Various surgical strategies were applied depending on the characteristics of the aneurysm. Good outcomes 3 months postoperatively were achieved in 77.1% and 89.3% for the overall and good-grade groups, respectively.

Conclusions

Microsurgery is a safe and effective treatment of VA and proximal PICA aneurysms. Moreover, the far-lateral approach without C1 laminectomy was adequate and effective for aneurysms located above the lower border of the foramen magnum.

Course of the V3 segment of the vertebral artery relative to the suboccipital triangle as an anatomical marker for a safe far lateral approach: A retrospective clinical study

Background:

The third segment of the vertebral artery (V3) is vulnerable during far lateral and retrosigmoid approaches. Although the suboccipital triangle (SOT) is a useful anatomical landmark, the relationship between V3 and the muscles forming the triangle is not well-described. We aimed to demonstrate the relationship between the V3, surrounding muscles, and SOT in clinical cases.

Methods:

Operative videos of patients with the vertebral artery (VA) and posterior inferior cerebellar artery (PICA) aneurysms treated with occipital artery-PICA bypass through the far lateral approach were examined. Videos from January 2015 to October 2021 were retrospectively reviewed to determine anatomy of the V3 and the SOT.

Results:

Fourteen patients were included in this study. The ipsilateral V3 was identified without injury in all patients using the bipolar cutting technique. The lateral 68.2% of the horizontal V3 segment, including the V3 bulge, was covered by the inferomedial part of the superior oblique muscle (SO). The medial 23.9% was covered by the inferolateral part of the rectus capitis posterior major muscle. The inferomedial part of the horizontal V3 segment is located within the SOT.

Conclusion:

Most of the V3, including the V3 bulge, were located beneath the SO and the inferomedial part of V3 located within the SOT. Elevation of the SO should be performed carefully using the bipolar cutting technique to avoid injury to the V3. To the best of our knowledge, this is the first description of the V3 relative to the SOT in the clinical setting.

Complex Intracranial Aneurysms

Complex intracranial aneurysms remain challenging to treat using standard microsurgical or endovascular techniques. These aneurysms often require a combination of deconstructive and reconstructive procedures, such as parent artery occlusion, flow alteration, and blind-alley formation with or without bypass surgery, for effective and enduring therapeutic effects. It is important to determine the type of bypass based on the site of occlusion of the patent artery, anatomical features of the distal vessels, and expected adequate blood flow. In this chapter, we describe the "Standards," "Advances," and "Controversies" in the context of a microsurgical treatment strategy for complex intracranial aneurysms. "Standards" include a combination of frequent and commonly used procedures that have been gathering a certain consensus on their effectiveness. "Advances" include infrequent, demanding, and/or uncertain surgical procedures that are currently under debate. Finally, "Controversies" discuss a number of unsolved issues.

The Intersection Between the Sternocleidomastoid and Splenius Capitis as the Anatomical Landmark to Facilitate Occipital Artery Harvest: A Retrospective Clinical Study

BACKGROUND

Occipital artery (OA)-posterior inferior cerebellar artery (PICA) bypass is a challenging procedure and is not frequently performed owing to the difficulty of OA harvest. To facilitate harvest, the intersection between the sternocleidomastoid and splenius capitis (the OA triangle) is used as the anatomical landmark to identify the OA segment that carries the highest risk of damage. This clinical study aimed to demonstrate efficacy and safety of OA harvest using this landmark.

METHODS

The study included 18 patients who underwent OA harvest using the OA triangle as a landmark for treatment of vertebral artery and PICA aneurysms. Patients were retrospectively evaluated for safety and patency of OA after harvest and OA-PICA bypass.

RESULTS

Of 18 patients with ruptured and unruptured vertebral artery and PICA aneurysms, 13 (72.2%) underwent OA-PICA bypass and 5 (27.8%) did not undergo bypass. The OA was completely harvested without damage in all patients. After harvest, the OA was patent in 17 patients (94.4%) and was occluded in 1 patient owing to vasospasm; this patient then underwent recanalization resulting in good patency of the OA-PICA bypass. The patency rate of the OA-PICA bypass was 100%.

CONCLUSIONS

The OA triangle, which is the anatomical landmark of the proximal end of the transitional segment of the OA, facilitated OA harvest using the distal-to-proximal harvest technique with safety and good patency. To the best of our knowledge, this is the first study of OA harvest in clinical cases.