Triphasic perfusion computed tomography in acute middle cerebral artery stroke - A correlation with angiographic findings

Objective: To evaluate the usefulness of triphasic perfusion computed tomog raphy (TPCT) in diagnosing middle cerebral artery (MCA) occlusion and in as sessing the perfusion deficit and collateral circulation in patients with a cute ischemic stroke. Background: Conventional angiography is the criterion standard for the diag nosis of MCA occlusion and for the assessment of perfusion deficit and coll ateral blood supply. The risk of hemorrhagic transformation after recanaliz ation of occluded arteries by thrombolytic therapy is considered high when pretherapeutic residual flow is markedly reduced. Patients and Methods: In 8 patients within 3 hours of onset of acute MCA st roke, precontrast computed tomographic scans were taken, and then TPCT was performed after power-injector controlled intravenous administration of con trast media. Sequential images of early, middle, and late phases were obtai ned. The whole procedure took 5 minutes. Perfusion deficit on TPCT was grad ed as "severe" or "moderate," depending on the state of collateral flow. Di gital subtraction angiography (DSA) was performed in all patients within 6 hours of acute stroke. Direct intra-arterial urokinase infusion was begun i mmediately after the angiographic superselection of the MCA occlusion site in 6 of the 8 patients within 7 hours of onset (range, 4.3-6.2 hours). Results: The DSA findings showed occlusion of the MCA stem (n=1) and at the bifurcation (n=4). The sites of proximal MCA occlusion could be identified on the early and middle images of TPCT in all 5 patients. On DSA findings, all 8 patients had a zone of perfusion deficit with markedly slow leptomen ingeal collaterals and a zone of perfusion deficit with no collaterals. The zone of severe perfusion deficit on TPCT corresponded to the zone of perfu sion deficit with no or few collaterals on angiography, and the zone of mod erate perfusion deficit on TPCT corresponded to that of perfusion deficit w ith markedly slow leptomeningeal collaterals. Early parenchymal hypoattenua tion on precontrast computed tomography was confined to the zone of severe perfusion deficit on TPCT. The initial National Institutes of Health Stroke Scale score correlated better with the total extent of severe perfusion de ficit and moderate perfusion deficit on TPCT than that of severe perfusion deficit alone. After direct intraarterial thrombolysis within 7 hours of on set, symptomatic hemorrhagic transformation did not develop in 4 patients w ith small severe perfusion deficit (33% or less of the presumed MCA territo ry). However, the remaining 2 patients with large severe perfusion deficit (more than 50% of the presumed MCA territory) deteriorated to death with he morrhagic transformation. Conclusions: Triphasic perfusion computed tomography is useful for diagnosi ng proximal MCA occlusion and assessing perfusion deficit and collateral ci rculation as reliably as DSA. The zone of severe perfusion deficit on TPCT may be presumed to be the ischemic core, and that of moderate perfusion def icit, the penumbra zone. Triphasic perfusion computed tomography may be use d as a rapid and noninvasive tool to make thrombolysis safer.