T2-weighted MRI correlates with long-term histopathology, neurology scores, and skilled motor behavior in a rat stroke model.

The intraluminal suture model of transient middle cerebral artery occlusion (MCAO) in the Sprague Dawley strain of rats characteristically results in an inconsistently sized brain lesion. The purpose of the investigation reported here was to determine whether there were strong point-to-point correlations between the degree of cortical lesion size, as assessed in vivo using T2-weighted magnetic resonance imaging (MRI) and corresponding cortical lesion size using routine histopathological techniques. Moreover, we aimed to investigate if cortical lesion size as determined by these two modalities correlates with neurological and/or skilled motor deficits observed in individual animals. Baseline behavioral scores were obtained on the animals prior to receiving 60 min of transient MCAO. Following MCAO, animals were tested for 1-21 days for neurological deficits. T2-weighted MRIs of the cortex were taken at two and seven days post-MCAO. At 30 and 60 days the rats were retested for forelimb dexterity in the staircase test. Subsequently, the cortex was examined for histopathological damage. Indeed, there were highly significant correlations between lesion size determined by MRI and histopathology. The degree of cortical damage observed in the T2-weighted MRI, as well as the size of the histopathological lesions were, in turn, highly correlated with the degrees of deficiencies observed in the composite neurological assessments and with the deficits involving skilled use of the contralateral forepaw (damaged side).