Cortical reorganization of language functioning following perinatal left MCA stroke.

OBJECTIVE: Functional MRI was used to determine differences in patterns of cortical activation between children who suffered perinatal left middle cerebral artery (MCA) stroke and healthy children performing a silent verb generation task.

METHODS: Ten children with prior perinatal left MCA stroke (age 6-16 years) and ten healthy age matched controls completed an executive language activation task. fMRI scans were acquired on a 3T scanner using T2* weighted gradient echo, echo-planar imaging (EPI) sequence. Random effects analysis and independent component analysis (ICA) were used to compute activation maps.

RESULTS: Both analysis methods demonstrated alternative activation of cortical areas in children with perinatal stroke. Following perinatal stroke, typical left dominant productive language areas in the inferior frontal gyrus were displaced to anatomical identical areas in the right hemisphere (p=.001). In addition, stroke patients showed more bilateral activation in superior temporal and anterior cingulate gyri and increased activation in primary visual cortex when compared to healthy controls. There was no relation between lesion size and the degree of right hemisphere activation. ICA showed that the healthy controls had a negative correlation with the time course in the right inferior frontal gyrus in the same region that was activated in stroke subjects.

INTERPRETATION: This functional MRI study in children revealed novel patterns of cortical language reorganization following perinatal stroke. The addition of ICA is complementary to Random Effects Analysis, allowing for the exploration of potential subtle differences in pathways in functional MRI data obtained from both healthy and pathological groups.