Uncommon Patterns of Intracranial Aneurysms: A Pictorial Essay

Intracranial aneurysms are relatively common, with a prevalence of approximately 4%. Unruptured aneurysms may cause symptoms mainly due to a mass effect, but the real danger is when an aneurysm ruptures, leading to a subarachnoid hemorrhage. Most aneurysms are asymptomatic and will not rupture, but they grow unpredictably and even small aneurysms carry a risk of rupture. There are many risk factors for the development of intracranial aneurysms, both inherited and acquired. Females are more prone to aneurysm rupture, with subarachnoid hemorrhage (SAH) 1.6 times more common in women. The prevalence of aneurysm increases in certain genetic diseases. There are four main types of intracranial aneurysms: saccular, fusiform (atherosclerotic or dolichoectatic type/congenital type), dissecting, and the mycotic type. The saccular type accounts for 90% of intracranial aneurysms. We observed some patients who were referred for diagnosis and further angiographic evaluation. They had presented with various histories and clinical findings. Their imaging findings such as CT scan, CTA, MRI and MRA findings were unusual. Every one of these patients has an uncommon form of aneurysm which could be misdiagnosed with other conditions or might need special and different treatment and knowledge of these situations could be of great help.