Half of moderate to severe traumatic brain injury patients had markedly impaired corpus callosum (CC) functioning and structural integrity that is associated with poor neurocognitive functioning, according to a study of children aged 8-19 years.

The researchers used high angular resolution diffusion-weighted imaging to determine the structural integrities of the CC in 32 children who had suffered a traumatic brain injury (TBI) and of the CC in 31 healthy children. Patients in the experimental group had suffered from a moderate to severe TBI 1-5 months prior to the study. The researchers assessed CC function through interhemispheric transfer time (IHTT) – the time required to transfer stimulus-locked neural activity between the left and right brain hemispheres. Each participant’s IHTT was calculated from recording electroencephalography, while he or she completed a computerized, pattern-matching task with bilateral field advantage.

Half of the TBI patients had significantly slower IHTTs than did the control group. The IHTTs of this so-called IHTT-slow TBI group deviated by at least 1.5 standard deviations from data for the healthy control group.

The IHTT-slow TBI group also demonstrated lower CC integrity and poorer neurocognitive functioning than did both the control group and the remaining members of the experimental group. Lower fractional anisotropy (FA) – a common sign of impaired white matter (WM) – and slower IHTTs also predicted poor neurocognitive function.

“When we compared the IHTT-slow TBI group to the healthy control group, we found significant differences in callosal WM integrity, as well as the integrity of the association and projection tract systems tested. Lower FA and higher mean diffusivity (MD) in the IHTT-slow group suggests myelin disruption,” noted Emily L Dennis of the University of Southern California, Marina del Rey, and her colleagues. “When we compared the IHTT-normal TBI group to the healthy control group, we found only a few areas where the TBI group had significantly lower FA and no significant differences in MD [mean diffusivity].”

Read the full study in the Journal of Neuroscience ( doi:10.1523/JNEUROSCI.1595-15.2015 ).