A significant reduction in the overall CC size as compared to the control group was reported by Paus et al. using T1-weighted MRI images from PEMCS group190. Reduced CC size was observed only in females, being most pronounced in the posterior third of CC (isthmus and splenium). The posterior third of CC mainly contains interhemispheric fibers forming parts of ventral and dorsal visual streams, and the small sized CC could be consequent to abnormalities in these interhemispheric fibers191. A subset of children in this study were subjected to magnetization transfer image acquisition. No effect of PEMCS on the magnetization transfer ratio based myelination index was demonstrable within any of the sections of CC, which implies that PEMCS specifically affects the size, but not the myelination of CC, possibly by interfering with the addition of axons during brain development. The authors suggest that the clinical ramifications of these findings may help explain the increased incidence of ADHD and association of PEMCS with impaired processing of visual stimuli.
