Uncommon Patterns of Intracranial Aneurysms: A Pictorial Essay

 Abstract

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.