Rat middle cerebral artery occlusion: correlations between histopathology, T2-weighted magnetic resonance imaging, and behavioral indices.

During attempts to develop the intraluminal suture model of transient middle cerebral artery occlusion (MCAO) in the Sprague Dawley strain of rats, we noticed a wide variability in lesion size seen with T2-weighed magnetic resonance imaging (MRI) or histopathology, as well as in scores for behavioral indices. It was our intent to examine the results of the study carefully and determine whether there were strong point-to-point correlations between the degree of lesion size determined from T2-weighted MRI or histopathology and intermediate or long-term neurologic/behavioral assessments. Baseline behavioral scores for forelimb dexterity (staircase test) were obtained on all animals in the period before receiving 60 minutes of transient MCAO. After MCAO, animals were tested at specified intervals from 1 to 21 days for composite neurologic deficits. T2-weighted MRI was taken at 2 and 7 days post-MCAO. At 30 and 60 days post-MCAO, animals were retested in the staircase test with subsequent histopathologic examination of the brains. Indeed, there were highly significant correlations between lesion size determined by MRI and histopathology. The damage observed in the T2-weighted MRI, as well as the size of the histopathologic lesions, were in turn highly correlated to deficiencies observed in the composite neurologic assessments, as well as to deficits at 30 and 60 days post-MCAO for skilled use of the contralateral forepaw (damaged side). In the latter test, the correlations were somewhat less significant for the ability of rats to reach for food with the ipsilateral forepaw (undamaged side).