Changes in Brain Volume, Blood Flow After Concussion

Athletes with a history of concussion show evidence of brain abnormalities months and years after injury, including changes in brain structure size, blood flow, and connectivity.

The cohort, made up of collegiate athletes from 7 different contact and non-contact sports, proves that the findings are relevant for the sports community as a whole.

In order to examine the potential long-term consequences of concussion, Nathan Churchhill, PhD, of St. Michael’s Hospital in Toronto, ON, Canada and colleagues used multi-modal MRI to describe abnormalities of structure and function in the brain — including cerebral blood flow, cortical volume, and white matter microstructure — of 43 college athletes (21 male, 22 female). Twenty-one participants had a history of concussion and 22 did not based on baseline assessment with the Sport Concussion Assessment Tool 3 (SCAT3).

Voxel-wise MRI measures showed the greatest volumetric decreases in the left cerebellum, temporal lobes, right precentral gyrus, supplementary motor area, and superior frontal lobes in athletes with prior concussion compared to those without. Volumetric increases were observed in the right hippocampus, left caudate, and cuneus. Reduced cerebral blood flow and gray matter volume were observed in the precentral gyrus, supplementary motor area, and superior frontal lobes, while increased cerebral blood flow was observed in the right hippocampus and the posterior cingulate, proximal to the cuneus.

A greater number of previous concussions was associated with increased volume in the parietal and occipital lobes and decreased volume in the insula bilaterally. Longer recovery time was linked to reduced volume in the temporal lobes, supplementary motor area, and anterior cingulated. Additionally, a greater number of prior concussions was associated with perfusion decreases in the frontal and temporal lobes. Longer recovery was associated with mainly focal increases in the cerebellum and middle occipital lobe, with minimal differences in cerebral blood flow.

The authors noted that volumetric increases seen in the hippocampus, caudate, and cuneus may indicate “cortical reorganization beyond simple atrophy. Although not, to our knowledge, previously reported in the concussion literature, cortical growth has long been recognized as part of neuroplastic adaptation in brain injury, e.g., stroke,” they said. “The regions showing significant differences are of particular interest, as they are implicated in emotion and visual attention, two domains that often show dysfunction after head injury. Given that athletes with prior history of concussion had no persistent symptom complaints, volumetric increases may reflect adaptation to preserve these domains following injury.”

“We want to emphasize that, in general, the health benefits of sport participation still outweigh the risk of concussion,” Tom Schweizer, PhD, of St. Michael’s Hospital, said in a statement. “Our findings can help to guide concussion management, and to minimize any future risk to athletes. The more we know about concussion, the better we can reduce these risks.”

Reference

Churchill N, Hutchison M, Richards D, Leung G, Graham S, Schweizer TA. Brain structure and function associated with a history of sport concussion: a multi-modal MRI study. J Neurotrauma. 2016 Jul 21. [Epub ahead of print].