Impact of contrast CT angiography and whole brain contrast CT perfusion study on the accuracy of cerebrovascular diagnosis in patients presenting with a major stroke-like syndrome
Objective: The diagnosis of ischemic stroke subtype is difficult in the emergency setting when based only upon a non-contrast CT scan and clinical findings. Accurate diagnosis may be important because prognosis depends upon the size and location of the infarct and emergency therapeutic decisions rest upon attempts to improve prognosis. Diffusion/perfusion weighted MR identifies acute ischemia and ischemic injury but is expensive, and not consistently accessible nationwide. We investigated the ability of a readily available CT contrast study (CT angiography, CTA; and whole brain CT perfusion, CTP) to enhance diagnostic accuracy of stroke subtype. Methods:All patients (1/97–12/98) who received a CTA within 24 hours of stroke onset (mean=4.6 hrs) and a follow-up CT or MRI within 2 weeks were analyzed (N=40). Stroke neurologists made stroke subtype diagnoses based upon: 1) non contrast CT and clinical vignette; 2) #1 and CTA; 2) #1, #2 and CTP. Diagnostic accuracy at each sequential step was measured against the gold standard based upon all available clinical, lab and follow-up imaging information. Results: The addition of the contrast CT study (CT+CTP)led to a statistically significant, relative improvement in accuracy of 1)infarct localization, 100%; 2) involved vascular territory, 69%; 3) occluded vessel, 94%; 4) TOAST stroke subtype, 44%; and 5) Oxfordshire stroke subtype, 81%. CTA led to significant improvement in diagnostic accuracy of vessel occlusion and TOAST subtype. CTP led to significant improvement in diagnostic accuracy of infarct localization, vascular territory and Oxfordshire classification. Conclusion: The addition of a contrast CT study to evaluate the intracranial vessels (CTA) and whole brain perfusion (CTP) enables highly accurate diagnosis of stroke subtype in the emergency setting. The ability of this widely accessible, emergency neuroimaging technique to predict functional outcome and guide therapeutic decisions can now be investigated.