Cerebral perfusion and diffusion in stroke: Association with aphasia severity in the early phases of recovery

Abstract

The purpose of this study was to investigate the relationship between aphasia severity and cerebral perfusion and lesion size in stroke. Nine subjects with acute ischemic stroke were examined within 24 hours of symptom onset and six were reexamined at one-month post-stroke. Examination included aphasia testing, testing of face discrimination ability, administration of the National Institutes of Health Stroke Scale, and perfusion MRI (PI), diffusion MRI (DWI), and T2-weighted MRI (T2-MRI). Subjects with a variety of aphasia types and a large range of aphasia severity participated in the study. MR images were visually inspected to verify perfusion and diffusion abnormalities. Perfusion abnormality was quantified by calculating a perfusion signal ratio of the affected hemisphere over the whole image (left/whole = ratio). Lesion volume was calculated from the DWI and T2-MRI. A perfusion abnormality larger than a DWI lesion was observed in 8 of 9 subjects. Minimal lesions were observed on DWI in three of the subjects while their PI revealed significant perfusion abnormality. Correlation coefficients (Spearman) between aphasia severity and hypoperfusion were significant in the acute stage and again at one-month post-stroke. Five of six subjects that were reexamined at one-month post-stroke experienced significant aphasia recovery. Visual inspection of their PI scans suggests that aphasia recovery was accompanied by increase in cerebral perfusion. The correlation between aphasia severity and lesion size was not statistically significant in the acute stage or at one-month post-stroke. Consequently, it is probable that cerebral hypoperfusion is a better predictor of aphasia severity and recovery in early stroke than lesion volume.