Anatomy and morphology of giant aneurysms--angiographic study of 125 consecutive cases.

BACKGROUND: Giant intracranial aneurysms are rare and heterogeneous lesions with complex vascular anatomy. The aim of this retrospective study was to provide a comprehensive description of the anatomical features of giant aneurysms. METHODS: We identified 125 patients with 129 giant aneurysms (≥ 25 mm) who were treated between 1987 and 2007 at the Department of Neurosurgery of Helsinki University Central Hospital (HUCH). All the imaging studies and medical records were reviewed for relevant information. RESULTS: The distribution of the giant aneurysms among regions was as follows: internal carotid artery (ICA) 39%, middle cerebral artery (MCA) 32%, vertebrobasilar and posterior cerebral artery (VB-PCA) region 25%, and anterior cerebral artery (ACA) including the anterior communicating artery 5%. The cavernous ICA segment (n = 21, 16%) and the MCA bifurcation (n = 25, 19%) were the most frequent specific locations. Half (n = 11) of all fusiform aneurysms were found in the VB-PCA region. As many as 41 % of the giant MCA aneurysms were ruptured. Major anatomic variations were found in three (2%) and multiple giant aneurysms in three (2%) patients. Wall calcification was noted in 24% and intraluminal thrombosis in 33% of ruptured giant aneurysms (n = 42). CONCLUSIONS: The majority of giant aneurysms are located in the ICA and MCA regions, while the ACA region is an exceptional site. The MCA region is the most common site for ruptured giant aneurysms. Associated anatomic variations and the multiplicity of giant aneurysms are a rare finding.