Specific and evolving resting-state network alterations in post-concussion syndrome following mild traumatic brain injury

Abstract

Post-concussion syndrome has been related to axonal damage in patients with mild traumatic brain injury, but little is known about the consequences of injury on brain networks. In the present study, our aim was to characterize changes in functional brain networks following mild traumatic brain injury in patients with post-concussion syndrome using resting-state functional magnetic resonance imaging data. We investigated 17 injured patients with persistent post-concussion syndrome (under the DSM-IV criteria) at 6 months post-injury compared with 38 mild traumatic brain injury patients with no post-concussion syndrome and 34 healthy controls. All patients underwent magnetic resonance imaging examinations at the subacute (1-3 weeks) and late (6 months) phases after injury. Group-wise differences in functional brain networks were analyzed using graph theory measures. Patterns of long-range functional networks alterations were found in all mild traumatic brain injury patients. Mild traumatic brain injury patients with post-concussion syndrome had greater alterations than patients without post-concussion syndrome. In patients with post-concussion syndrome, changes specifically affected temporal and thalamic regions predominantly at the subacute stage and frontal regions at the late phase. Our results suggest that the post-concussion syndrome is associated with specific abnormalities in functional brain network that may contribute to explain deficits typically observed in PCS patients.

Figure 1. Association of modularity (left) and local efficiency of superior frontal regions (right) with symptom severity in mTBI patients at the late phase.

Figure 2. Statistical connectograms of differences between mTBI patients and controls, showing significant effect in regional characteristics at the subacute and late phases after the injury at p<0.05 (uncorrected).

The outermost ring shows brain regions arranged by lobe and subcortical structures and further ordered anterior-to-posterior (color map is lobe-specific). Bottom right: legend of the representation of regional metrics in the connectogram. Within the circular structure representing the brain parcellation, two sets of seven circular heat maps (or rings) are shown. Each set encodes for the subacute and late phases after the injury respectively, while each heat map encodes for regional graph theory properties (basic and topological) associated with the corresponding parcellation. Proceeding inward towards the center of the circle, these measures are: nodal centrality and efficiency, local efficiency, degree, edge diversity and strength. Red (resp. blue) color represents positive (resp. negative) effect.

Figure 3. Brain regions with significant group differences in basic graph properties (s and d_e) between mTBI patients and controls at p<0.05 (uncorrected).

The node size indicates the number of basic properties with significant group differences. The nodal regions are located according to their centroid stereotaxic coordinates. Nodal color code for the average size effect, hot (resp. cold) colors represent increased (resp. decreased) properties.

Figure 4. Brain regions with significant group differences in topological graph properties (k, E_l, E_n and bc) between mTBI patients and controls at p<0.05 (uncorrected).

The node size indicates the number of topological properties with significant group differences. The nodal regions are located according to their centroid stereotaxic coordinates. Nodal color code for the average size effect, hot (resp. cold) colors represent increased (resp. decreased) properties.