Patients with fusiform aneurysms can present with subarachnoid hemorrhage (SAH), mass effect, ischemia, or unrelated symptoms. The absence of an aneurysm neck impedes the direct application of a clip and endovascular coil deployment. To evaluate the effects of their treatments, the authors retrospectively analyzed a consecutive series of patients with posterior circulation fusiform aneurysms treated at Stanford University Medical Center between 1991 and 2005.Forty-nine patients (mean age 53 years, male/female ratio 1.2:1) treated at the authors' medical center form the basis of the analysis. Twenty-nine patients presented with an SAH. The patients presenting without SAH had cranial nerve dysfunction (five patients), symptoms of mass effect (eight patients), ischemia (six patients), or unrelated symptoms (one patient). The aneurysms were located on the vertebral artery (VA) or posterior inferior cerebellar artery (PICA) (21 patients); vertebrobasilar junction (VBJ) or basilar artery (BA) (18 patients); and posterior cerebral artery (PCA) (10 patients). Pretreatment clinical grades were determined using the Hunt and Hess scale; for patients with unruptured aneurysms (Hunt and Hess Grade 0) functional subgrades were added. Outcome was evaluated using the Glasgow Outcome Scale (GOS) score during a mean follow-up period of 33 months. Overall long-term outcome was good (GOS Score 4 or 5) in 59%, poor (GOS Score 2 or 3) in 16%, and fatal (GOS Score 1) in 24% of the patients. In a univariate analysis, poor outcome was predicted by age greater than 55 years, VBJ location, pretreatment Hunt and Hess grade in patients presenting with SAH, and incomplete aneurysm thrombosis after endovascular treatment. In a multivariate analysis, age greater than 55 years was the confounding factor predicting poor outcome. Stratification by aneurysm location removed the effect of age. Of 13 patients with residual aneurysm after treatment, five (38%) subsequently died of SAH (three patients) or progressive mass effect/brainstem ischemia (two patients).Certain posterior circulation aneurysm locations (PCA, VA-PICA, and BA-VBJ) represent separate disease entities affecting patients at different ages with distinct patterns of presentation, treatment options, and outcomes. Favorable overall long-term outcome can be achieved in 90% of patients with PCA aneurysms, in 60% of those with VA-PICA aneurysms, and in 39% of those with BA-VBJ aneurysms when using endovascular and surgical techniques. The natural history of the disease was poor in patients with incomplete aneurysm thrombosis after treatment.
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