Feasibility of endoscopic endonasal approach for clip application of cerebral aneurysms: a systematic review.

INTRODUCTION: While open, microsurgical clipping and endovascular coiling remain the gold standards for treatment of cerebral aneurysms, a growing number of aneurysms treated via endoscopic endonasal methods have been reported in the literature. The aim of this study was to conduct a systematic review of the literature to gain a more thorough appreciation of the potential benefits and drawbacks of the endoscopic endonasal strategy in this setting.

EVIDENCE ACQUISITION: We performed a detailed systematic review of the medical literature on endoscopic endonasal skull base surgery for treatment of cerebral aneurysms utilizing the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We identified 9 clinical studies describing treatment of 23 aneurysms utilizing the EEA. 11 additional cadaveric studies investigating aspects of operative exposure and/or technique in this setting were identified. The full text of these articles was reviewed.

EVIDENCE SYNTHESIS: In the 9 clinical studies that met inclusion criteria, 23 aneurysms were treated in 21 patients. The mean patient age was 52.6 years. 15 aneurysms were unruptured and 8 were ruptured. 14 aneurysms involved the anterior circulation and 9 involved the posterior circulation. In 21 of 23 aneurysms, complete occlusion was achieved with endonasal clipping. Two aneurysms required additional treatment that included a takeback for clip repositioning and staged endovascular coiling. Complications included post-operative CSF leak (23.8%), stroke (19%), and meningitis (14.3%). Analysis of the combined literature revealed a significantly higher rate of CSF leak with endonasal clipping of posterior circulation aneurysms compared to anterior circulation aneurysms (P=0.047, Fisher's Exact Test). While there was a trend towards increased post- operative neurologic deficit following EEA for posterior circulation aneurysms, this did not reach statistical significance (P=0.063). The majority of post-operative complications in posterior circulation aneurysms occurred during clip application of aneurysms at the level of the basilar apex. In addition to the aforementioned clinical reports, 11 cadaveric studies were identified. 4 of these reports investigated approaches for individual anterior circulation aneurysms, 5 investigated approaches for posterior circulations aneurysms, and 2 involved both anterior and posterior circulation aneurysms.

CONCLUSIONS: Despite a moderate increase in utilization, caution should be exercised when choosing an endonasal strategy for treatment of aneurysmal pathology over more traditional and established methods such as microsurgical clip application and endovascular methods. Anecdotal evidence suggests that inferior and/or medial projecting aneurysms involving the paraclinoid ICA not amenable to traditional open/endovascular strategies may be reasonable to consider for EEA clip application. Wide-necked, midline, ventrolaterally-projecting aneurysms involving the vertebrobasilar system may represent an additional exception, as long as the location along the rostrocaudal axis is low enough so as not to compromise visualization. Future improvements in operative technology, including anticipated advances in endoscopic 3-D visualization, may further alter the landscape of treatment involving this complex pathology.