Subarachnoid hemorrhage and aneurysms.

Ruptured intracranial aneurysms are the usual cause of acute subarachnoid hemorrhage (SAH). Noncontrast CT is the primary imaging procedure of choice for establishing the diagnosis of SAH. Conventional contrast angiography is the gold standard for establishing the presence of intracranial aneurysms, but CT and MRI have supplementary roles. The pathogenesis, presentation, and imaging of SAH and intracranial aneurysms are discussed.