DIFFERENTIATION BETWEEN TRANSIENT ISCHEMIC ATTACK AND ISCHEMIC STROKEWITHIN THE FIRST 6 HOURS AFTER ONSET OF SYMPTOMS BY USING TC-99M-ECD-SPECT

The aim of this study was to define the accuracy of Tc-99m-ethyl cyste inate dimer-single photon emission computed tomography (Tc-99m-ECD-SPE CT) in distinguishing transient ischemic attack from completed ischemi c stroke at early stages after the onset of symptoms. In a prospective study we examined 82 patients within 6 hours after the onset of sympt oms (neurologic deficit caused by middle cerebral artery ischemia) usi ng both Tc-99m-ECD-SPECT and computed tomography (CT). The follow-up w as based on Scandinavian Stroke Scale (SSS) 24 hours and 5-7 days, as well as on CT 7 days, after the event. SPECT evaluation was performed both visually and using semiquantitative region-of-interest (ROI) anal ysis. According to visual SPECT analysis, on admission 59 of 82 patien ts had activity deficits in the symptomatic hemisphere. After 7 days, all these patients had neurologic symptoms (SSS 28 +/- 12 points), cau sed by a cerebral infarction as evidenced with CT. Twenty-three of 82 patients displayed no early activity deficit despite clinical symptoms . None of these patients had neurologic symptoms after 7 days (indicat ing transient ischemic attack or prolonged reversible ischemic neurolo gic deficit). In the semiquantitative SPECT analysis, all patients had abnormal count densities in the respective ROI (activity <90% compare d with the contralateral side). All patients with transient ischemia ( n = 23) had count rate densities more than 70% of the respective contr alateral ROI, whereas all patients with subsequent infarction (n = 59) had values < 70%. Use of Tc-99m-ECD-SPECT allows transient ischemia t o be distinguished from ischemic infarction using relative regional ac tivity thresholds within the first 6 hours after onset of symptoms.