Traumatic Brain Injury: Risk Factors and Biomarkers of Alzheimer's Disease and Chronic Traumatic Encephalopathy

Abstract

A complex interaction between genetic and environmental risk factors has often been a suspected trigger for the development of neurodegenerative disease. Yet of all the possible environmental risk factors, trauma to the central nervous system is one of the most consistent candidates for initiating the molecular cascades that result in several neurodegenerative diseases including Alzheimer's disease (AD). In almost all of the studies investigating traumatic brain injury and AD risk, AD was diagnosed based on clinical criteria for probable or possible AD, without neuropathological verification. Recent evidence also suggests that mild traumatic brain injury, including repetitive concussions and subconcussive trauma, can provoke another distinctive neurodegeneration termed chronic traumatic encephalopathy. Because most reports were based on clinical diagnostic criteria that may lack the specificity to rule out other causes of dementia, it is possible that the increased incidence of dementia following head injuries is due to CTE, alone or in conjunction with other neurodegenerative conditions such as AD. The search for, and validation of, biomarkers for specific neurodegenerative diseases provide disease diagnosis and indicators of risk and disease progression, and offer a means to monitor therapeutic efficacy.