Brain Injury Lingers at Least 4 Months After Concussion

November 26, 2013

Although symptoms have usually resolved, there is still evidence of brain injury 4 months after a concussion, a new study shows.

The study was conducted by a team led by Andrew R. Mayer, PhD, University of New Mexico School of Medicine in Albuquerque.

"My take-home message is even though symptoms appear to have resolved, the brain is still injured for several months after concussion, and it may not be safe to return to activities where mild brain traumatic injury may be experienced again," Dr. Mayer told Medscape Medical News.

He said it was not possible from this study to give advice on how long the brain takes to return to normal. "But I would say that the current advice that the patient just sits out for a week is really not satisfactory. Our results suggest a much longer period is needed for healing. If it was my child with a concussion I would try and preclude activities that might result in another mild traumatic brain injury for at least a couple of months and probably longer."

Their results were published online November 20 in Neurology.

Increased Diffusion

For the study, Mayer and colleagues evaluated 50 patients with mild traumatic brain injury and compared them with 50 controls matched for age, sex, and education.

Participants underwent a battery of clinical and neuroimaging tests approximately 14 days after the injury, with 26 patients returning for follow-up 4 months after injury.

Clinical measures included tests of attention, processing speed, executive function, working memory, memory, and self-reported postconcussive symptoms. Neuroimaging studies recorded measures of diffusion and atrophy for cortical and subcortical structures.

Results showed that patients with concussion reported more cognitive, somatic, and emotional symptoms during the first 2 weeks, but these were significantly reduced at the 4-month time point.

Patients with concussion also showed evidence of brain injury, signaled by increased diffusion in the bilateral superior frontal cortex at 2 weeks, with this measurement remaining elevated in the left superior frontal cortex at 4 months. The increase equated to about 10% compared with values in the controls.

Dr. Mayer explained that the increased diffusion signals the movement of water in the brain. "This probably reflects the taking up of water by cells during injury — known as cytotoxic edema — which is associated with cellular changes in astrocytes, neurones, and glial cells in animal studies. It could also be the result of reactive gliosis, the change in shape of glial cells in response to damage to the central nervous system."

There were no significant differences between patients and matched controls on neuropsychological testing or measures of gray matter atrophy/mean diffusivity at either time point, suggesting that frank neuronal or neuropil loss does not occur early in the chronic disease course for patients with typical mild traumatic brain injury.

Clinical Implications?

Dr. Mayer believes the diffusion changes seen could have potential clinical implications. "Our results certainly could have long-term implications. We know repetitive concussions increase the risk of developing chronic encephalopathy, and there is evidence that if you have had one concussion you are more likely to suffer another one, so these finding may have important implications about when it is truly safe to resume physical activities that could produce a second concussion, potentially further injuring an already vulnerable brain."

He compares healing from concussions to recovering from a burn. "During recovery, reported symptoms like pain are greatly reduced before the body is finished healing, when the tissue scabs. The same appears to be true for concussion."

But he says that any conclusions drawn from this study have to be seen as speculative. "Right now we have no biological markers for mild traumatic brain injury, and it's hard to be sure what our results mean from a clinical standpoint. All we can say is the brain is not fully healed at 4 months."

He added that it is not known how long it will take for the brain to go back to normal after a single mild traumatic brain injury. "We need to determine the natural recovery course," he said. "We would like to follow these patients up long term to shed more light on this, but we have no funding for this at present."

The study was supported by the National Institutes of Health.

Neurology. Published online November 20, 2013. Abstract

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