The study by Stern et al offers valuable information, but the relationships between various features of chronic traumatic encephalopathy (CTE) still are not well understood, said Allan H. Ropper, MD, executive vice chair of neurology at Harvard Medical School in Boston, in an accompanying editorial (N Engl J Med. 2019 Apr 10. doi: 10.1056/NEJMe1903746). The risk of CTE associated with a long period of playing football does not correspond with the number, severity, or serial occurrence of concussions, he observed. In addition, “individual factors such as the player’s size, head-to-neck configuration, style of play, and position, as well as biologic attributes, may influence the deposition of tau.” Because of the absence of an association between neuropsychological test results and tau deposition, neurologists can draw few conclusions based on the presence of neuropsychological abnormalities in athletes who are at risk for CTE, said Dr. Ropper.

“As with Alzheimer’s disease, the CTE field is in a phase of fumbling with circumstantial evidence for a connection between tau deposition and a clinical syndrome. ... The report in this issue certainly does strengthen the case that tau is the offender early in CTE, but other links remain to be clarified,” he concluded.

Dr. Ropper reported no relevant conflicts of interest. He is deputy editor of the New England Journal of Medicine.