Intracranial Aneurysms in the Context of Variant Cerebrovascular Anatomy: A Review of the Literature.

BACKGROUND: The cerebrovascular anatomy varies, with many associated variants and persistent channels. Many such vessels have been reported to carry an increased risk of intracranial aneurysm (IA) formation. We conducted a systematic literature review of IAs associated with variant anatomy. METHODS: We performed a systematic review without a meta-analysis in accordance with the PRISMA (preferred reporting items for systematic reviews and meta-analyses) guidelines for studies involving IA formation in patients with variant anatomy. Studies were excluded if 1) the IAs were associated with malformations; 2) the variant anatomy discussed was in the form of segment hypoplasia or aplasia; 3) the anatomical variants were discussed secondary to the intervention; 4) insufficient information had been included; or 5) they were literature reviews. RESULTS: A total of 64 studies had met the inclusion and exclusion criteria for the final review. IA rupture was present in 91 of 131 cases (69.5%). Of the 131 IAs, 45 (34.3%) had been associated with an anomalous vessel origin or course, 43 with segmental fenestration (32.8%), 26 with a primitive persistent anastomosis (19.8%), and 17 with multiple or accessory vessels (12.9%). A total of 122 IAs (93.1%) had been treated with endovascular (64 of 122; 52.5%), microsurgical (57 of 122; 43.5%), or combined (1 of 122; 0.8%) methods. CONCLUSIONS: Variant, anomalous, and persistent primitive anatomy have often been reported in association with IA formation. These lesions present with a high proportion of rupture and warrant a low threshold for treatment. Preservation of perfusion is critical because such vessels developmentally exist to maintain flow.

Basilar Artery Bands: Anatomic and Histologic Study with Application to Coiling and Stenting Procedures.

BACKGROUND: Internal bands of the basilar artery (BA) have been rarely studied. Because bands could have obvious consequences in patient diagnosis and care, the present multiinstitutional cadaveric study was performed. METHODS: The intraluminal bands of BAs were studied in 80 cadaveric specimens derived from India (Group 1) and the United States (Group 2). Their orientation within the vessel was recorded. Measurements included the length of the BA, diameter of the BA, intraluminal band length and thickness, and distance of the band to the vertebrobasilar junction. Selected bands were submitted for histologic analysis. RESULTS: In Group 1, an intraluminal band (all vertically oriented) was identified in 16.6%. The mean length and thickness of the bands were 2.04 mm and 1.33 mm, respectively. These bands were located at a mean distance of 1.74 mm superior to the vertebrobasilar junction. In Group 2, an intraluminal band was identified in 6%. One band was vertically positioned, and 2 were horizontally positioned. The mean length and thickness of the bands were 2.5 mm and 0.9 mm, respectively. These latter bands were located at a mean distance of 2.23 mm superior to the vertebrobasilar junction. Histologically, the bands were essentially extensions of the tunica media and interna of the artery. CONCLUSIONS: To our knowledge, this study is the first multiethnic study of the prevalence and morphometry of the BA bands. A better understanding of these bands may help reveal their relationship to thrombus and aneurysmal formation and their impact on endovascular procedures.