Having multiple (3-5+) concussions may disrupt the brain’s default mode network

By Ian Scott. This article was initially published in our Concussion Update newsletter; please consider subscribing.

An abstract presented at the Radiological Society of North America (RSNA) 2021 Annual Meeting demonstrated that “multiple concussions [three to five] seem to disrupt the brain’s default mode network (DMN), which could increase the risk of long-term cognitive disruption,” according to an article in Medscape.

Utilizing resting-state functional MRI (fMRI), researchers led by Thomas Johnson, M.D, Ph.D., examined the DMN of adolescents and young adults enrolled in a clinic for persistent post-concussive symptoms, as well as a matched control group. The DMN is “active in internal goal-oriented and conceptual cognitive tasks,” as well as non-task-oriented processes such as daydreaming, thinking about the future, and recalling memories.

Compared to the age- and sex-matched control group, there was “no difference in the connectivity in the DMN in patients who had experienced 1 or 2 concussions,” according to a press release by the Radiological Society of North America. However, in patients who sustained three to five concussions, there was a disruption in the DMN. 

These results indicate that concussions may be a “two-tier disease,” where several concussions have different consequences than one or two concussions, which will help athletes make more informed return-to-play and retire-from-play decisions. 

Johnson hopes to perform a study on the same patients five years from now to see if the disruption in the DMN is persistent, which hopefully offers a fuller picture of the long-term consequences of concussions. While the scientific committee reviewed this abstract for the Radiological Society of North America conference, it has not been peer-reviewed or published yet.