Predictive Value of ^99mTc-HMPAO-SPECT for Neurological Outcome/Recovery at the Acute Stage of Stroke

Abstract

Background and Purpose: Combined perfusion and oxygen metabolism PET imaging is highly predictive of spontaneous outcome after middle cerebral artery (MCA) stroke, independent of clinical scores, but whether the assessment of perfusion alone by SPECT provides similar information remains unclear. We have assessed the prognostic value of ^99mTc-HMPAO-SPECT at the acute stage of stroke. Methods: Twenty-seven first-ever nonhemorrhagic MCA territory stroke patients were prospectively studied 4–20 h (mean: 12 h) after onset with ^99mTc-HMPAO-SPECT. None was part of a therapeutic trial or received thrombolysis. Neurological deficits were quantified at admission and 2 months later with Orgogozo’s MCA scale. SPECT images were visually classified by 3 independent observers into one of three patterns, as follows: pattern I = marked and extensive tracer hypofixation; pattern II = moderate and/or focal hypofixation with or without combined hyperfixation, and pattern III = normal or increased uptake without hypofixation. In addition to this visual analysis, we also calculated a voxel-based ‘hypoperfusion score’, an index of severity × extent of hypofixation according to Mountz’s method. Results: There was a good intra- and interobserver agreement. After consensus, 9, 14 and 4 patients were classified in patterns I, II and III, respectively. These patterns had a significant predictive value for raw outcome but not for percentage recovery (p = 0.008 and p = 0.127, respectively). Thus, all patients in pattern III had a good outcome, while most (but not all) patients in pattern I had a poor or intermediate outcome; pattern II patients were more evenly distributed among outcomes. Hypoperfusion scores were highly significantly positively correlated with both 2-month outcomes and percentage recoveries, even after controlling the predictive value of day 0 MCA scores by partial correlations. Comments: We found that SPECT had a significant added predictive value even when compared to admission neurological scores. Although less accurate than PET, ^99mTc-HMPAO-SPECT may help to predict spontaneous individual neurological evolution, especially whenever perfusion images are normal or show an increased tracer uptake without associated hypofixation.

The Quest for Early Predictors of Stroke Evolution

“…However, even in the same clinical subgroup, we observed a wide spectrum of outcomes. Indeed, it is known from daily clinical practice and from recent single-photon emission CT studies 27 that patients presenting with the same symptoms may subtend diverse etiologies and perfusional deficits. This variability, which remains unrevealed in Bamford's classification, may explain the different therapeutic response and the clinically relevant frequency of intracranial hemorrhage after thrombolysis.…”

The Concept of Ischemic Penumbra in Acute Stroke and Therapeutic Opportunities

“…Other studies have suggested that patients with a normal SPECT scan, performed within 3–6 h from stroke onset, will most likely recover spontaneously and therefore may not benefit from thrombolysis [50,51,52]. Furthermore, studies performed at a later time after the onset of symptoms could also identify different tissue compartments and SPECT results could help predict neurological development in addition to neurological scores [53, 54]. …”

Ischaemic Penumbra: Highlights

“…[12] Several studies have highlighted the validity of HMPAO-SPET as a prognostic tool in ischaemic stroke by showing a correlation between the size and=or the degree of hypoperfusion and neurological and functional outcome. [13][14][15] However, apart from assessing and visualizing CBF, SPET does not provide any information on the metabolic state of brain, thus limiting its use in the evaluation of the pathophysiology and outcome of the ischaemic penumbra. Moreover, the occurrence of spontaneous reperfusion of necrotic tissue in the first 48 hours after stroke prevents SPET from distinguishing tissue still at risk of infarction from already infarcted brain areas.…”