Concussions are non-structural injuries that cannot be detected by routine neuroimaging or, simply put, invisible brain injuries. Strong hits on the head can lead to temporary changes in neuronal functioning, which are associated with short-term symptoms, such as dizziness or nausea, as well as long-term effects, such as memory loss or depression.
“But, concussions are just the tip of the iceberg,” warned Stern. Sub-concussive blows, resulting from hits on the head or even heading in soccer, can also lead to long-term effects on neuronal functioning without having immediate concussion-like symptoms. The extent of these unnoticed brain injuries can be tremendous. Football players, for example, receive 2,000 to 3,000 blows per season, each at 20 – 30 g. In comparison, a headed soccer ball has an average of 15 g, but can reach up to 60 g. In order to provide the audience with a basis for comparison, Stern said, “A car driving at 35 mph into a brick wall corresponds to about 20 g.” A possible long-term repercussion of these repetitive brain injuries can be Chronic Traumatic Encephalopathy (CTE), a neurodegenerative disease similar to Alzheimer’s. Stern’s case study showed that repetitive sub-concussive blows are very likely to result in CTE, as 34 of 35 professional Football players who were examined had developed the disease. Although CTE begins early in life, the symptoms, such as memory loss, depression and aggression, appear years or decades after the brain trauma and continue to increase, with most cases progressing to full-blown dementia. Unfortunately, CTE can only be diagnosed postmortem, said Stern.
The study conducted by Koerte and her team paves the way for a possible future diagnosis of CTE while an individual is alive. The usage of an advanced neuroimaging technique helped to visualize heading-related sub-concussive brain traumas in living subjects. “My job is to make the invisible visible,” said Koerte. The study compared 12 professional male soccer players with 11 professional male swimmers. None of the, on average, 20-year-old participants showed a history of symptomatic concussion. The images revealed that heading leads to alterations of the brain’s structure, metabolism, and function, which resemble tissue alterations of mild traumatic brain injuries.
The postmortem description of CTE has already had a great impact on public policy and awareness. As a reaction to the latest scientific research, sports leagues in the U.S. and Germany have started to introduce new regulations. Nevertheless, “we are at the infancy of this knowledge,” said Stern. The underlying mechanisms are not yet clear. “What we need to do now is find a way to diagnose it during life.”
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