Investigators at Washington University School of Medicine and the University of Milan in Italy have peered inside the brains of patients who have had a severe head injury to study hour-by-hour changes in the amount of amyloid beta, a protein that is believed to play a key role in Alzheimer's disease.
This experiment was a test of a model that suggests brain injury accelerates harmful processes that cause Alzheimer's. The results of the study contradicted researchers’ expectations, which hypothesized that injuries, such as those caused by vehicle accidents and falls, would lead to an increase in amyloid beta levels.
Instead, they found recovery from brain injury, rather than the injury itself, seemed to increase amyloid beta.
Levels dropped when neurological condition worsened, but rose when they improved.
In the study, 18 patients recovering from traumatic brain injuries had amyloid beta levels measured using intracerebral microdialysis, which involves placing a small catheter into the brain tissue to sample the fluid in the spaces between cells.
A previous study in 2005 showed the amyloid-D peptide plays a central pathophysiological role in brain cell communication and Alzheimer's disease, but little is known about the concentration and dynamics of it in the human brain. Further investigation is needed to answer exactly why brain injury increases risk of Alzheimer's disease.