Computed tomography in cerebral aneurysms with special emphasis on giant intracranial aneurysms.

The computed tomography (CT) findings of 105 patients with a total of 139 intracranial aneurysms are analyzed. The rate of detection of subarachnoid and intracerebral hemorrhage in relation to time since bleeding episode agreed well with previously reported results. Direct visualization of small intracranial aneurysms using 5 mm sections in the postcontrast scan was possible in 58% of the cases. Ten cases of giant intracranial aneurysms (GIA) more than 25 mm in diameter are analyzed in depth. Diagnostic criteria for differentiation of GIA from tumors are discussed. Ring shaped postcontrast enhancement of the outer margin of the aneurysm or curvilinear interrupted calcifications were found in totally or partially thrombosed GIA; central or peripheral homogeneous enhancement of the aneurysm's lumen (target sign) was typical of partially thrombosed GIA; and nonthrombosed GIA usually presented as homogeneously enhancing lesions. Differential diagnostic criteria are discussed.