Purpose: To determine the value of perfusion computed tomography (CT) in prediction of the clinical course and late functional outcome in patients with acute ischaemic stroke who had unremarkable initial brain CT examination.
Material and methods: Single slice perfusion CT was performed in 55 consecutive patients (27 women, mean age 67 +/- 11 years) with acute ischaemic stroke within 6 hours (median 2.26 hours) from onset of symptoms. Values of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) obtained from affected hemisphere were compared to respective values in non-affected hemisphere (relative parameters). Initial neurological deficits were estimated using NIH Stroke Scale (NIHSS) score and correlated with perfusion CT values, employing Spearman rank correlation coefficient (r). Values of perfusion CT parameters in prediction of functional outcome were determined by comparing against scores on modified Rankin Scale (mRS) and Glasgow Outcome Scale (GOS) after three months of onset of stroke.
Results: All perfusion CT parameters significantly correlated with initial neurological deficit. The highest correlation with the NIHSS was found for relative CBF, which correlated better than absolute CBF (rCBF r = 0.69; CBF r = 0.50, P < 0.001). In prediction of favourable outcome (mRS <or= 2) the commonly employed thresholds (in parentheses) and associated sensitivity, specificity, positive and negative predictive values were: 87%, 44%, 79%, and 58% for CBF (10 ml/min/100 g), 59%, 81%, 88%, and 49% for rCBF (48%), 49%, 56%, 73%, and 31% for CBV (2 ml/100 g), 87%, 44%, 79% and 58% for rCBV (60%), 41%, 81%, 84% and 36% for MTT (6 s) and 54%, 81%, 87% and 49% for rMTT (145%), respectively, while for prediction of excellent outcome (mRS <or= 1), the only statistically significant respective accuracy measures were for rCBV, 90%, 35%, 60%, 75%, and for rCBF, 62%, 69%, 69% and 62%.
Conclusions: In patients within the first 6 hours from stroke onset, and without a hypodensity sign on initial routine CT examination, perfusion CT provides quantitative parameters that correlate well with initial neurological status and late functional outcome.