PICA aneurysms: case report and review of the literature

An aneurysm is defined as a localised dilation of a blood vessel secondary to disease or weakening of the vessel wall. Studies by radiographic and autopsy series on 10 to 15 million people have shown the prevalence of intracranial saccular aneurysms to be about 5% in the United States. Intracranial aneurysms commonly occur at bifurcations and branching points of the large arteries of the Circle of Willis. Approximately 85% of intracranial aneurysms develop in the anterior part of the Circle of Willis, with the remaining 15% found in the vertebrobasilar system. The majority of aneurysms are discovered after an episode of subarachnoid haemorrhage (SAH).