EXPERIENCE WITH COMPUTED TOMOGRAPHIC ANGIOGRAPHY FOR THE DETECTION OFINTRACRANIAL ANEURYSMS IN THE SETTING OF ACUTE SUBARACHNOID HEMORRHAGE

OBJECTIVE: To objectively compare computed tomographic angiography (CT A) with selective digital subtraction angiography (DSA) in the detecti on and anatomic definition of intracranial aneurysms, particularly in the setting of acute subarachnoid hemorrhage (SAH). METHODS: In a blin ded prospective study, 40 patients with known or suspected intracrania l saccular aneurysms underwent both CTA and DSA, including 32 consecut ive patients with SAH in whom CTA was performed after CT images were o btained diagnostic for SAH, The CT angiograms were interpreted for the presence, location, and size of the aneurysms, and anatomic features, such as the number of aneurysm lobes, aneurysm neck size (less than o r equal to 4 mm), and the number of adjacent arterial branches were as sessed. The images obtained with CTA were then compared with the image s obtained with DSA, with the latter images serving as controls. RESUL TS: DSA revealed 43 aneurysms in 30 patients and ruled out intracrania l aneurysms in the remaining 70 patients. For aneurysm presence alone, the sensitivity and specificity for CTA was 86 and 90%, respectively. For the presence of an aneurysm, six CT angiograms showed false negat ive results and one CT angiogram showed a false positive result. False negative results were usually caused by technical problems with the i mage, tiny aneurysm domes (<3 mm), and unusual aneurysm locations (i.e ., intracavernous carotid or posterior inferior cerebellar artery aneu rysms), The results obtained with CTA were, compared with the results obtained with DSA, more than 35% accurate in determining dome and neck size of aneurysm, aneurysm lobularity, and the presence and number of adjacent arterial branches. In addition, CTA provided a three-dimensi onal representation of the aneurysmal lesion, which was considered use ful for surgical planning. CONCLUSION: CTA is useful for rapid and rel atively noninvasive detection of aneurysms in common locations, and th e anatomic information provided in images showing positive results is at least equivalent to that provided by DSA. In cases of SAH in which die nonaugmented CT and CTA results indicate a clear source of bleedin g and provide adequate anatomic detail, we think it is possible to for ego DSA before urgent early aneurysm surgery. In all other cases, DSA is indicated.