Concussions disrupt the brain’s ability to clean itself

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Traumatic brain injuries (TBIs) involve sudden damage to the brain caused by a head injury, such as falls, vehicle-related collisions, violence, sports injuries or combat injuries. TBIs can range from mild concussions to severe brain damage. Millions of individuals worldwide are affected by TBIs each year, but those most at risk include:

  • Children, primarily newborns to 4-year olds,
  • Young adults, between the age of 15-24,
  • Adults, age 60 and older,
  • Males in any age group.

It has been recently established that even mild TBIs can cause long lasting effects, such as anxiety, depression, Alzheimer’s, dementia, and more. Despite TBIs being a global and pressing medical issue, the precise consequences of TBIs is still unclear and improved treatments are desperately needed.

Source: TheraSpecs, “10 Symptoms of Moderate or Severe Traumatic Brain Injury (TBI)”, Bullock (2018).

A new study published in Nature from the University of Virginia School of Medicine explored the effect of TBIs on the brain in the long-term. By studying mice with TBIs, the researchers gained crucial new insights on TBIs!

When the brain swells following a TBI, it presses against the skull. In between these, there are lymphatic vessels responsible for cleaning the brain that get trapped, known as the meningeal lymphatics. The pressure imposed on these vessels may cause serious long-lasting impairment to the brain’s ability to ‘clean’ itself. These vessels have also been found to play an important role in cognitive decline with age and Alzheimer’s. Therefore, this may be where the relationship between TBIs and Alzheimer’s stems from. The authors of the study also believe that this may be the reason for the development of anxiety or depression following TBIs.

Brain meningeal lymphatics used for cleaning. Source: “Human and nonhuman primate meninges harbor lymphatic vessels that can be visualized noninvasively by MRI”, eLife, Absinta, et al. (2017).

Additionally, the study found that people with pre-existing brain damage are likely to suffer more severe consequences from TBIs. This was demonstrated in mice, where previous damage led to additional brain inflammation and worse outcomes (such as memory impairment). This is essential to consider for sport players or those in the military, for example, who wish to continue what they were previously doing following a TBI, exposing themselves to greater risks.

The researchers stated that they are hoping to, one day, be able to rejuvenate the impaired lymphatic vessels, via medications for example, to improve a patient’s outcome and reduce the long-term consequences.

Study source: Bolte, A.C., Dutta, A.B., Hurt, M.E. et al. “Meningeal lymphatic dysfunction exacerbates traumatic brain injury pathogenesis”. Nature Communications. 11, 4524 (2020).
Link: https://doi.org/10.1038/s41467-020-18113-4

Featured image source: Ahn, J.H., Cho, H., Kim, J. et al. Meningeal lymphatic vessels at the skull base drain cerebrospinal fluid. Nature 572, 62–66 (2019).

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