To the Editor.—I noted with interest the recent publication by Prensky et al,1 confirming past observations of transiently abnormal brain scans in patients with focal seizures. To answer Dr. Schultz's question, there is indeed a means of differentiating stroke from a seizure focus on the brain scan.
One must perform a "flow" study, obtaining rapid sequential scinti-photos over the cerebral circulation following the intravenous bolus injection of the technetium isotope. When there is hypoperfusion of the same hemisphere that later manifests an infarct pattern on follow-up scan, one can confidently diagnose a cortical stroke.2,3 The data are now so compelling for this combination of findings that we now include a flow study as part of the routine brain scan.
In the case of hemiparesis secondary to focal fits, the isotope flow to the involved hemisphere should be normal.