Dissecting aneurysms of the posterior inferior cerebellar artery: report of four cases and review of the literature.

Dissecting aneurysms frequently involve the vertebral arteries and their branches, but those exclusively on the posterior inferior cerebellar artery (PICA) represent only 24 cases in the literature, including the four cases discussed in this article. The clinical diagnosis lacks pathognomonic signs or symptoms, with presentations such as subarachnoid haemorrhage or ischaemia of the brain stem or the cerebellum, and the management is controversial. Wrapping, clipping and embolisation of the aneurysms were tried in this series with different outcomes. Exclusion of the pathological segment should be performed, as shown by rebleeding from our case which was wrapped or by progression of the vascular disease in cases where treatment was delayed. Surgical or endovascular occlusion are well tolerated in our cases and in those reported from the literature, which implies the absence of normal perforating branches to the brain stem arising from the proximal dissected segment of the PICA and a good collateral circulation. A revascularisation procedure using the occipital artery can be performed in order to prevent infarction if an endovascular test occlusion is not tolerated.