Published Online
on July 7, 2005

A more recent version of this article appeared on August 1, 2005

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Submitted on January 10, 2005
Accepted on February 8, 2005

"Clinical-CT" Mismatch and the Response to Systemic Thrombolytic Therapy in Acute Ischemic Stroke

David M. Kent MD, MS^*; Michael D. Hill MD, MS; Robin Ruthazer MPH; Shelagh Coutts MBChB; Andrew M. Demchuk MD; Imanuel Dzialowski MD; Olaf Wunderlich MD; and Rudiger von Kummer MD

From the Institute for Clinical Research and Health Policy Studies (D.M.K., R.R.), Department of Medicine, Tufts-New England Medical Center, Tufts University School of Medicine, Boston, Mass; the Department of Clinical Neurosciences (M.D.H., S.C., A.M.D.), University of Calgary, Calgary, Canada; and the Department of Neuroradiology (I.D., O.W., R.v.K.), University of Technology, Dresden, Germany.

^* To whom correspondence should be addressed. E-mail: dkent1{at}tufts-nemc.org.

Background and Purpose--Mismatch between clinical deficits and imaging lesions in acute stroke has been proposed as a method of identifying patients who have hypoperfused but still have viable brain, and may be especially apt to respond to reperfusion therapy. We explored this hypothesis using a combined database including 4 major clinical trials of intravenous (IV) thrombolytic therapy.

Methods--To determine what the radiological correlates of a "matched" functional deficit are, we calculated the relationship between the ASPECT score of the 24-hour (follow-up) CT scan and the 24-hour National Institutes of Health Stroke Scale (NIHSS) score on the subsample with ASPECT scores performed at this time (n=820). Based on this empirical relationship, we computed the absolute difference between the observed baseline ASPECT score and the "expected" score (ie, matched) based on baseline NIHSS for all patients (n=2131). We tested whether patients with better than expected baseline ASPECTS were more likely to benefit from IV recombinant tissue plasminogen activation (rtPA).

Results--At 24 hours, there was a strong, linear, negative correlation between NIHSS and ASPECTS (r²=0.33, P<0.0001); on average, an increase of 10 points on NIHSS corresponded to a decrease of 3 points on ASPECTS. At baseline, the average degree of mismatch between the observed and "expected" ASPECTS was 2.1 points (interquartile range, 1.0 to 3.4). However, multiple analyses failed to reveal a consistent relationship between the degree of clinical-CT mismatch at baseline and a patient’s likelihood of benefiting from IV rtPA.

Conclusion--Clinical-CT mismatch using ASPECT scoring does not reliably identify patients more or less likely to benefit from IV rtPA.

Key words: cerebrovascular accident • computed tomography • emergency treatment • neuroimaging • stroke, acute • stroke, ischemic • thrombolytic therapy

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