Even mild concussions cause severe and long-lasting impairments in the brain’s ability to clean itself of toxins, and this may seed it for Alzheimer’s disease, dementia and other neurodegenerative problems, new research from the University of Virginia School of Medicine, published in Nature Communications, reveals.

“This provides some of the best evidence yet that if you haven’t recovered from a brain injury and you get hit in the head again, you’re going to have even more severe consequences. This reinforces the idea that you have to give people an opportunity to heal. And if you don’t, you’re putting yourself at a much higher risk for long-term consequences that you might not see in a year but could see in a couple of decades.”

— John Lukens, PhD, of UVA’s Department of Neuroscience and the Center for Brain Immunology and Glia (BIG)

Unknown Consequence of TBI?

Lukens’ research suggests a previously unknown consequence of TBI that can have long-lasting effects. When the brain swells, it presses against the skull; trapped in-between are tiny lymphatic vessels that clean the brain. This pressure on the vessels, the UVA researchers found, causes serious and long-lasting impairment of the brain’s ability to purge itself of toxins.

Working with lab mice, the scientists found the impairment could last at least 2 weeks and possibly much longer.

These lymphatic vessels were identified by Jonathan Kipnis, PhD, and his collaborators at UVA in 2015. Until then, medical textbooks insisted the vessels did not exist and that the brain was “immune privileged,” meaning that it did not interact with the immune system. Kipnis’ discovery changed all that, and he has since determined the vessels play important roles in both Alzheimer’s and the cognitive decline that comes with age.

Now they emerge as an important player in TBI, a media release from the University of Virginia Health System explains.

“We know that traumatic brain injury carries an increased risk for a bunch of long-term issues like dementia, Alzheimer’s disease and CTE [chronic traumatic encephalopathy], and this has really been made extra public because of the NFL. Then there’s also anxiety, depression, suicide. The reasons why TBI results in increased risk for this isn’t totally known, and we think that our findings might provide a mechanism as to why.”

— researcher Ashley C. Bolte, an MD/PhD student

Who Are Most at Risk?

People who have pre-existing problems with their brain drainage, either from prior concussions or naturally, are likely to suffer much more severe consequences from TBI, according to the research. In mice, this led to more brain inflammation and worse outcomes, including memory impairment.

“If you have a pre-existing kink in the pipes and you get hit in the head, then everything is taken to a higher level — the impacts on memory, the neuroinflammation. There are a lot of implications to it.”

— John Lukens, PhD

Some Good News

Emerging imaging technology may eventually make it possible for doctors to identify people who will suffer the greatest consequences of TBI. Doctors may also one day be able to rejuvenate the impaired lymphatic vessels with drugs to improve patients’ outcomes and possibly stave off long-term consequences. This also may prove useful in the battle against the cognitive decline that naturally occurs with age, the release continues.

In addition, Lukens adds, it eventually may be possible for doctors to evaluate brain drainage after injury to determine when it is safest for patients to return to action.

“Right now, we really don’t know what to tell these kids who want to get back out on the field, or even members of the military. It would be important to have empirical tests to say you can continue or never to do those things ever again.”

[Source(s): University of Virginia Health System, Science Daily]

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