Perfusion-weighted CT predicts stroke outcome after thrombolysis


WESTPORT, CT (Reuters Health) – Besides approximating final infarct size in stroke patients with complete recanalization after thrombolysis, perfusion-weighted CT (PWCT) predicts which patients will have poor clinical outcomes, according to a report in the September issue of Stroke.

"Perfusion-weighted CT is a technique that uses conventional CT scanning with contrast (a standard technique) to simultaneously acquire images of the cerebral vasculature (CTA or CT angiography, used to detect intravascular clot) and of blood flow to the brain parenchyma (CT perfusion or CTP, used to assess tissue level perfusion)," Dr. Michael H. Lev from Massachusetts General Hospital and Harvard Medical School in Boston explained to Reuters Health.

Dr. Lev and colleagues performed PWCT in 22 consecutive patients with middle cerebral artery occlusion who underwent intra-arterial thrombolysis and compared the results with final infarct size and clinical outcomes.

Overall initial infarct volume (as determined by PWCT hypodensity) correlated significantly with follow-up infarct volume (p < 0.002), the authors report, especially for the patients who achieved complete or partial recanalization.

Initial lesion volumes were slightly larger than final volumes in the complete recanalization group, the report indicates, and smaller than final volumes in the groups with partial or no recanalization.

Clinical outcomes were poor in all patients whose initial PWCT lesion volumes were greater than 100 mL, the researchers note. In contrast, all patients with initial volumes below 100 mL who had partial or complete recanalization experienced good or fair outcomes.

In fact, clinical outcome and initial infarct size were linearly related in the complete (p = 0.03) and partial (p = 0.05) recanalization groups, the results indicate, but not in the no-recanalization group (p = 0.71).

"By its ability to predict those patients more–rather than less–likely to benefit from MCA recanalization, PWCT can play an important role in guiding acute stroke treatment," the authors conclude.

"Because CTA with CTP is fast, convenient, and relatively inexpensive compared to MRI, it may prove to be an ideal first screening test in patients with acute stroke who are being considered for thrombolytic treatment–patients in whom 'time is brain'," Dr. Lev said.

"We are not advocating CT 'over' MRI," Dr. Lev cautioned. "Diffusion-weighted MR remains the 'gold standard' for the sensitive detection of acute stroke. We are simply saying that the addition of CTA/CTP to the already routine noncontrast CT is an efficient means of getting critical data that aids in quick and efficient decision-making."

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