Voxel-based morphometric analysis (VBM) of the MRI scans of a group of adolescents, born preterm with very low birth weights and with deficits in judgment of line orientation, was used to demonstrate anomalies of cortical gray matter in a study at the Institute of Child Health and Great Ormond Street Hospital, London, UK. Subjects were assigned to 2 groups, deficit and no deficit, 11 in each, based on their scores on the Benton Judgment of Line Orientation test. IQ scores were average in both groups, and Block Design was the only WISC-III subtest showing a significant difference between groups (Deficit group=7.8; No Deficit group=10.4; p<0.05). All were neurologically normal and the MRIs showed no consistent abnormalities (thinning of the corpus callosum in 2 of the No Deficit group and 1 of the Deficit group and small hippocampi in 4 of the Deficit group). VBM analysis of scans identified a decrease in gray matter density and increase in white matter density in the ventral extrastriate cortex in children with visuospatial deficits, most prominent in the right hemisphere. These anomalies of cortical architecture were situated close to a temporooccipital area previously implicated in the line orientation task. [1]
COMMENT. Children born preterm may have cognitive deficits involving visuospatial processing of line orientation, despite normal neurologic examination and absence of specific abnormalities on conventional MRI. Subtle abnormalities of extrastriate cortex can be identified by analysis of voxel-based morphometry of MRI scans.