Differentiation between Transient Ischemic Attack and Ischemic Stroke within the First Six Hours after Onset of Symptoms by Using ^99mTc-ECD-SPECT

Abstract

Summary: The aim of this study was to define the accuracy of 99 mTc-ethyl cysteinate dimer-single photon emission com puted tomography e 9 mTc-ECD-SPECT) in distinguishing tran sient ischemic attack from completed ischemic stroke at early stages after the onset of symptoms. In a prospective study we examined 82 patients within 6 hours after the onset of symp toms (neurologic deficit caused by middle cerebral artery isch emia) using both 99 mTc-ECD-SPECT and computed tomogra phy (CT). The follow-up was 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) analysis.According to visual SPECT analysis, on admission 59 of 82 patients had activity deficits in the symptomatic hemisphere. After 7 days, all these patients had neurologic symptoms (SSS 28 ± 12 points), caused by a cerebral infarction as evidencedThe consideration of new and aggressive therapies in patients with acute focal cerebral ischemia calls for re liable diagnostic information within a short therapeutic window. Within this period the following specific infor mation is required: whether the symptoms are caused by stroke, where the stroke is located, and what subtype of stroke it is (Brass, 1997). Moreover, prognostication of the course of stroke is urgently required because it may range from complete neurologic restitution after a few 921with CT. Twenty-three of 82 patients displayed no early activ ity deficit despite clinical symptoms. None of these patients had neurologic symptoms after 7 days (indicating transient isch emic attack or prolonged reversible ischemic neurologic defi cit). In the semiquantitative SPECT analysis, all patients had abnormal count densities in the respective ROI (activity <90% compared with the contralateral side). All patients with tran sient ischemia (n = 23) had count rate densities more than 70% of the respective contralateral ROI, whereas all patients with subsequent infarction (n = 59) had values < 70%. Use of 99 mTc-ECD-SPECT allows transient ischemia to be distin guished from ischemic infarction using relative regional activ ity thresholds within the first 6 hours after onset of symptoms.

Comparative Overview of Brain Perfusion Imaging Techniques

“…Perfusion SPECT provides valuable information in acute stroke with respect to complications, 26 outcome, 27,28 or choice of treatment strategy. 29 In chronic cerebrovascular disease, SPECT assessment of functional reserve capacity may guide decisions regarding vascular surgery.…”

Imaging-Based Decision Making in Thrombolytic Therapy for Ischemic Stroke

“…While SPECT and especially positron emission tomography (PET) may render semiquantitative and quantitative hemodynamic data, 45,46 these modalities are not widely available and thus are of academic interest but probably will not have any practical implications for the general stroke patient in the near future.…”

Guidelines and Recommendations for Perfusion Imaging in Cerebral Ischemia

“…It is more difficult to clinically differentiate those neurological deficits due to ischemia that are likely to improve or reverse spontaneously from those that are likely to persist or worsen, and this is a significant value of perfusion imaging. [12][13][14][15][16][17] The demonstration of a normal level of CBF suggests that reperfusion has occurred spontaneously and that no acute vascular thrombolysis or flow augmentation is necessary. 18 -20 The level of perfusion to the ischemic tissues may help to determine the relative benefits and risks of a given therapy.…”