Atypical intracranial aneurysms: spectrum of imaging findings in computed tomography and magnetic resonance imaging.

We aim to describe demographics, clinical presentation, and spectrum of CT and MRI features suggestive of atypical intracranial aneurysms. The imaging protocols used for the diagnosis of intracranial aneurysms were thoroughly reviewed, including different CT and MRI protocols. We classified atypical aneurysms according to their location, size, clinical presentation, and specific imaging features. Dissecting aneurysms are one of the causes of stroke in young adults that may show intimal flap and double lumen. Traumatic intracranial aneurysms are a rare but serious complication of head injuries. Mycotic aneurysms are small and multiple at distal branch points with a high risk of rupture. Aneurysms with vasculitis are fusiform with a wide neck at a non-branch point that may be associated with vessel wall enhancement. Atherosclerotic aneurysms are usually large fusiform that affect large arteries. Oncotic aneurysms are relatively rare. They were reported to occur in patients with left atrial myxoma. Our study represented a wide spectrum of atypical intracranial aneurysms with their detailed diagnostic imaging findings on MRI and CT including newly introduced MRI sequences, which greatly influenced early diagnosis and timely management.