Using cortical pattern matching algorithms and techniques for measuring cortical thickness in the same cohort mentioned earlier, Sowell et al. reported significant cortical thickness excesses, up to 1.2mm, in bilateral temporal, inferior parietal and right frontal regions in the PEA group when compared to control subjects. Verbal recall and visuo-spatial measures correlated strongly with the right dorsal frontal and left occipital region thicknesses, respectively147. It should be noted that gray matter density and cortical thickness are not identical measures, as each provide unique and independent information. Gray matter density essentially reflects the proportion of tissue that has gray matter signal value on MRI, relative to other tissue types. Cortical thickness, however, reflects regional structural integrity. It is a specific measure of cortical anatomy, reflecting intrinsic alterations within the gray matter, and is unaffected by sulcal widening or other CSF related effects148. With progressive myelination, pruning of synaptic connections and, consequently, cortical thinning, occurs during normal brain development and maturation149. The findings of this study provide evidence that synaptic pruning and myelination may not be occurring normally, or may be disrupted in children with PEA.
