Chronic traumatic encephalopathy (CTE) is a syndrome caused by repeated head trauma resulting in cumulative neurocognitive and neuropsychiatric symptoms. CTE is characterized by progressive cognitive impairment (executive dysfunction, memory changes), neuropsychiatric symptoms (personality or behavioral changes, depression), and parkinsonism as well as speech and gait abnormalities.

While the incidence of CTE is unknown, it has been well described in populations at risk for repetitive traumatic brain injury (TBI) such as professional football players, boxers, and soldiers in combat. Risk of developing CTE increases with an increased frequency and severity of TBI and with older age.

Symptoms of CTE may not present until years following TBI. Pathologically, CTE is defined by deposition of abnormal tau proteins and degenerative changes that are distinct from other forms of dementia. Diagnosis is made either on a clinical basis (probable) or pathologically from postmortem examination (definite). Prognosis is variable depending on the extent of injury, and recovery is unlikely.