Concussions often result in cognitive impairments, balance deficit, mood disturbances, and a range of other symptoms. But what happens when a person experiences multiple concussions?

Athletes, especially those playing contact sports like ice hockey or football, are at an increased risk of sustaining multiple concussions. It is estimated that a third of all individuals who have sustained a traumatic brain injury (TBI) will experience another one. For instance, previous studies found that college football players with a concussion history are more likely to sustain another concussion compared to players who have never had a concussion. 

The effects of sustaining multiple concussions

Past studies of athletes with a history of concussions revealed that those who have sustained three or more concussions took longer to recover compared to those with one or no previous concussion. More specifically, those who have sustained three or more concussions had more enhanced unresolved impairment on cognitive tasks eight days after their concussion compared with athletes who had one concussion. 

Reaction time was also slower to return to baseline levels after injury in those who sustained two concussions compared to the athletes who had experienced one concussion. 

These athletes also experienced longer duration of migraine-cognitive-fatigue symptoms which consist of headache, dizziness, fatigue, drowsiness, sensitivity to light/noise, feeling slowed down, mentally foggy, and difficulty remembering/concentrating compared to individuals who had experienced one concussion.

Do symptoms accumulate when sustaining multiple concussion?

Some theories suggest that cumulative cognitive effects occur when people are subjected to multiple concussions where the deficits build up with every concussion sustained. However, there is no definite answer to whether this actually occurs due to limitations in studying this topic and the conflicting evidence. However, studies have reached the same conclusion that recovery slows down, the number of symptoms increase, and cognitive abilities are poorer when individuals sustain multiple concussions.

Does the brain look different due to multiple concussions?

TBI has been linked to cerebral atrophy or the loss of brain cells. Aging is also associated with mild brain volume loss as well as cognitive deficits. TBI can cause accelerated aging, especially memory deficits. A study compared the volume of specific brain regions and found that the left hippocampus, the area that supports memory formation and retention, has atrophied faster in former football athletes who have sustained multiple concussions compared to control.

The smaller left hippocampus was associated with the verbal memory deficits that are experienced after concussions. Additionally, the number of years they played football, a proxy for the number of concussions endured, is associated with smaller hippocampal volume and an atrophied amygdala (the emotional part of the brain). Therefore, in these former football players, repeated concussions could lead to greater atrophy and neuronal death than expected for their age which could indicate accelerated aging of the brain.

Written by Lea Farah

References

Covassin, T., Moran, R., & Wilhelm, K. (2013). Concussion symptoms and neurocognitive performance of high school and college athletes who incur multiple concussions. The American Journal of Sports Medicine, 41(12), 2885-2889. https://doi.org/10.1177/0363546513499230

Misquitta, K., Dadar, M., Tarazi, A., Hussain, M. W., Alatwi, M. K., Ebraheem, A., Multani, N., Khodadadi, M., Goswami, R., Wennberg, R., Tator, C., Green, R., Colella, B., Davis, K. D., Mikulis, D., Grinberg, M., Sato, C., Rogaeva, E., Louis Collins, D., & Tartaglia, M. C. (2018). The relationship between brain atrophy and cognitive-behavioural symptoms in retired canadian football players with multiple concussions. NeuroImage Clinical, 19, 551-558. https://doi.org/10.1016/j.nicl.2018.05.014

Yumul, J. N., & McKinlay, A. (2016). Do multiple concussions lead to cumulative cognitive deficits? A Literature review. Pm & r, 8(11), 1097-1103. https://doi.org/10.1016/j.pmrj.2016.05.005