Link between brain trauma and degenerative brain disease revealed

A new study suggests that just a single traumatic brain injury can generate an abnormal form of the dementia associated protein tau.

Published in the journal Brain, the study from the Mario Negri Institute for Pharmacological Research of Milan and the University of Glasgow provides first evidence that just a single brain injury can lead to an abnormal form of the dementia associated protein tau which can then slowly spread through the brain, resulting in memory deficits and neuronal damage.

“As part of this study we analysed brain specimens from patients surviving a year or more after a single, severe traumatic brain injury,” added Dr Willie Stewart, Honorary Clinical Associate Professor, Institute of Neuroscience and Psychology, University of Glasgow. “In this material we saw evidence of much more widespread deposits of abnormal tau proteins in brain injured patients than in normal control brains.”

In parallel the team observed the same type of abnormal tau in injured mice, which, over time, spread from the site of injury to involve remote brain regions. This progressive spread of tau was reminiscent of the spreading of prions, the infectious proteins more commonly associated with diseases such as CJD.

This observation – that a single brain trauma is associated with widespread tau deposition in humans and to the formation of a self-propagating form of tau ­– provides the first evidence for how a mechanical brain injury might evolve into chronic degenerative brain disease, including chronic traumatic encephalopathy (CTE).

“Traumatic brain injury is a leading cause of death and disability in young adults,” said Dr Elisa Zanier who led the Mario Negri Institute team with Dr Roberto Chiesa. “Moreover, even in milder cases, it represents a risk factor for dementia, such as CTE. Understanding the mechanism linking an acute mechanical event to a progressive, degenerative brain disease would help the development of new therapies.”