Rest for longer than a day is critical for allowing the brain to recover from short-term injuries and reset neural networks after a concussion, according to research published in the American Journal of Pathology.
Researchers from Georgetown University Medical Center also found that repeated, mild concussions with only a day of recovery between each injury led to increasing damage and brain inflammation that persisted a year after the last injury.
“It is good news that the brain can recover from a hit if given enough time to rest and recover,” Mark Burns, PhD, assistant professor of neuroscience at GUMC and director of the Laboratory for Brain Injury and Dementia, said in a statement. “But on the flip side, we find that the brain does not undertake this rebalancing when impacts come too close together.”
Often, mouse-model studies of concussion only examine impacts in the single digits. In order to investigate the types of brain damage that occur after sports, military, or domestic abuse injuries, the researchers of this mouse-model study examined the effect of repeated mild head trauma.
The investigators developed a mouse-model to induce repetitive, very mild concussive impacts while mice were anesthetized. They then compared how the mouse brains responded to a single concussion, how they responded to concussive impacts received daily for 30 days, and how they responded to concussive impacts received weekly for 30 weeks.
Mice with a single injury temporarily lost 10% to 15% of the neuronal connections in their brains, but no inflammation or cell death resulted, Dr Burns noted. After 3 days of rest, all neuronal concussions were restored. This pattern also held in mice that had a week of rest between concussive impacts but not in mice subjected to daily concussions.
Inflammation and damage to the brain’s white matter results when mild concussions occurred daily for 30 days. “This damage became progressively worse for 2 months and remained apparent 1 year after the last impact,” Dr Burn said.
“[These] findings mirror what has been observed about such damage in humans years after a brain injury, especially among athletes,” Dr Burns said. “Studies have shown that almost all people with single concussions spontaneously recover, but athletes who play contact sports are much more susceptible to lasting brain damage. These findings help fill in the picture of how and when concussions and mild head trauma can lead to sustained brain damage.”
Winston CN, Noël A, Neustadtl A, et al. Dendritic spine loss and chronic white matter inflammation in a mouse model of highly repetitive head trauma. Am J Pathol. 2016; doi:10.1016/j.ajpath.2015.11.006. In press.