A study published online Thursday in Brain, a journal of neurology, presents that repetitive hits to the head, separate from or in addition to known concussions, can cause CTE, just as concussions are believed to potentially lead to CTE. The researchers analyzed human brains — from four teenagers and young adults who had been exposed to mild head impact but died from another cause soon after. They found early evidence of brain pathology (focal phosphorylated tau protein) in two of the four brains that was consistent with what is seen in CTE, and early-stage CTE in one case.
The researchers note that clearly, not every individual who sustains a head injury, even if repeated, will develop CTE brain pathology. While clinicopathological correlation in the case series suggests that closed-head impact injury can trigger early brain pathologies associated with CTE, the causal mechanisms, temporal relationships, and contextual circumstances that link specific brain pathology to a particular antemortem insult are impossible to ascertain with certainty based solely on post-mortem neuropathology.