Alternate links: Google News | Twitter

Chronic traumatic encephalopathy, or CTE, is a degenerative brain disease that can only be diagnosed with a brain dissection after death. Because of that, most research about the disease has relied on brains donated to researchers by families or by individuals themselves, many of whom had seen or experienced symptoms, such as memory loss or major mood swings, that led them to believe they might have the disease.

That dynamic has long muddied the picture about the actual prevalence of CTE " especially for combat veterans exposed to traumatic brain injuries, or current and former elite-level athletes in contact sports like American football and ice hockey, where blows to the body and head are a regular occurrence.