The clinical presentation of chronic traumatic encephalopathy.

Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disorder attributed to repetitive mild traumatic brain injury. The diagnosis in a living individual can be challenging and can be made definitively only at autopsy. The symptoms are often nonspecific and overlap with neurodegenerative disorders such as Alzheimer's disease (AD) and frontotemporal dementia (FTD). Higher exposure to repetitive head trauma increases the risk of CTE. Genetic risk factors such as presence of an apolipoprotein E ε4 allele may be important. Individuals have varying degrees of cognitive, behavioral, and motor decline. Limitations in the manner in which data have been obtained over the years have led to different clinical descriptions of CTE. At present, there are no biomarkers to assist in the diagnosis. Standard neuroimaging may show nonspecific atrophic changes; however, newer imaging modalities such as positron emission tomography (PET) and diffusion tensor imaging (DTI) show promise. Neuropsychological testing may be helpful in determining the pattern of cognitive or behavioral decline.