Longitudinal structural connectomic and rich-club analysis in adolescent mTBI reveals persistent, distributed brain alterations acutely through to one year post-injury

TL;DR

This longitudinal diffusion MRI study reveals persistent, diffuse brain network alterations in adolescents after mTBI, with changes in global topology and rich-club subnetworks from acute to one-year post-injury.

Contribution

It provides novel longitudinal insights into structural connectome changes and rich-club network dynamics in adolescent mTBI over one year.

Findings

Global network topology becomes more diffuse post-injury

Rich-club subnetworks show increased density and integrity over time

Alterations persist up to one year post-injury

Abstract

The diffused nature of mild traumatic brain injury (mTBI) impacts brain white-matter pathways with potentially long-term consequences, even after initial symptoms have resolved. To understand post-mTBI recovery in adolescents, longitudinal studies are needed to determine the interplay between highly individualised recovery trajectories and ongoing development. To capture the distributed nature of mTBI and recovery, we employ connectomes to probe the brain's structural organisation. We present a diffusion MRI study on adolescent mTBI subjects scanned one day, two weeks and one year after injury with controls. Longitudinal global network changes over time suggests an altered and more 'diffuse' network topology post-injury (specifically lower transitivity and global efficiency). Stratifying the connectome by its back-bone, known as the 'rich-club', these network changes were driven by the 'peripheral' local subnetwork by way of increased network density, fractional anisotropy and decreased diffusivities. This increased structural integrity of the local subnetwork may be to compensate for an injured network, or it may be robust to mTBI and is exhibiting a normal developmental trend. The rich-club also revealed lower diffusivities over time with controls, potentially indicative of longer-term structural ramifications. Our results show evolving, diffuse alterations in adolescent mTBI connectomes beginning acutely and continuing to one year.