  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.
