Protein deposits associated with Alzheimer’s disease have been found in the brains of people who have suffered a head injury, according to a two-part study published in Neurology. While past research has linked brain trauma to an increased dementia risk later in life, the present findings may help explain the biological changes that cause this effect.

"Although previous research has shown that some head injury patients have these amyloid plaques shortly after the incident, these findings suggest these plaques are still present in the brains of patients over 10 years later. This helps shed light on why brain injury patients seem to be at increased risk of dementia — and may help us develop treatments that reduce this risk,” Dr Gregory Scott, lead author of the paper, said in a statement.

Researchers collected data from 28 patients: Nine who had suffered traumatic brain injuries, nine healthy patients, and 10 with Alzheimer’s disease. The participants underwent a brain scan that used a technique that allows scientists to view amyloid plaques, which are thought to be a hallmark of Alzheimer's disease. The patients with head injuries were found to have more amyloid plaques than the healthy volunteers, but fewer than those with Alzheimer's disease.

Specifically, the clumps were mainly found in the posterior cingulate cortex — a highly active area in the center of the brain involved in controlling attention and memory, and the cerebellum — a region at the base of the brain involved in motor control and coordination.

For the second part of the study, researchers examined the impact the head injuiries had on the so-called white matter — a component of the central nervous system, found in the deep tissues of the brain, that enables cells to communicate with each other. They found that amyloid plaque levels in the posterior cingulate cortex were related to the amount of white matter damage, suggesting that injury to the brain's wiring may be linked to the formation of amyloid plaques.

Although the study is limited by its size, researchers believe their findings provide hope for developing treatments to remedy the long-term effects of head injuries. 

"[The study] supports the idea that the window of treatment for brain injury is potentially months or even years after the initial event. If we can find out exactly what processes are going on in the brain, it may be that we can intervene and improve long-term outcomes for patients,” Scott said.

Alzheimer’s disease usually begins with mild memory loss and can progress until patients lose the ability to carry on a conversation or carry out their daily activities.   In 2013, about 5 million Americans were living with Alzheimer’s disease, with 14 million expected by 2050, according to the Centers for Disease Control and Prevention.

Scott G, Ramlackhansingh A, Hellyer P, et al. Amyloid pathology and axonal injury after brain trauma.  Neurology. 2016.