Blister-like Aneurysms in Atypical Locations: A Single-Center Experience and Comprehensive Literature Review

Objective: Blister-like aneurysms (BLAs) were originally described to arise typically along the nonbranching segment of the dorsal wall of the internal carotid artery (ICA); however, BLAs located in areas other than the dorsal ICA have been described more recently. We present a case series of "atypical" BLAs and a systematic review of the literature on this subject. Methods: We conducted a literature search using the key word "blister-like aneurysm." Studies reporting BLAs in locations other than the dorsal ICA wall were selected. Clinical presentation, treatment modality, complications, and outcomes (modified Rankin Scale for neurologic outcomes and Roy scale for radiologic outcomes) were extracted from each study. We also reviewed our single-institution experience with atypical BLAs and analyzed the topography and outcomes of all the atypical BLAs according to each specific treatment modality. Results: Atypical BLAs were observed in the anterior communicating, middle cerebral, basilar, posterior cerebral, anterior cerebral, and posterior inferior cerebellar arteries. Surgery was the treatment in 65% of patients, an endovascular approach was used in 30%, and a combined approach was used in 5%. A good outcome (modified Rankin Scale 0-1-2) was experienced by 88% and 55% of the patients in the endovascular and surgical groups, respectively. There were 4 deaths, 2 in the endovascular group and 2 in the surgical group. Conclusions: Endovascular treatment of BLAs seems to be associated with reduced morbidity and mortality and to provide a better outcome compared with surgical approaches. Further prospective studies are needed to confirm these results. It is important for clinicians to remember that BLAs may also occur in sites other than the typical ICA location.