Published on December 3, 2013 at 1:50 AM
•The presence of abnormal tau proteins in the brain may not be a reliable indicator of CTE. For example, various case studies have found that between 20 percent and 50 percent of subjects who had abnormal tau deposits nevertheless did not have any symptoms. "Older persons without dementia can accumulate Alzheimer's disease pathology (including tau deposition) without any associated cognitive or clinical symptoms," Karantzoulis and Randolph write. "The actual clinical significance of 'abnormal' tau deposition in the brains of retired athletes therefore remains unclear."
The authors detail how CTE originally was identified in 1928 as "punch drunk" syndrome in boxers. There is a striking parallel between the controversy over CTE today and punch drunk syndrome decades ago. In 1965, for example, a skeptic argued that punch drunk syndrome symptoms seen in boxers could have been due to alcoholism and venereal diseases, which were common in boxers at the time.
"One cannot deny that boxing and other contact sports can potentially result in some type of injury to the brain," Karantzoulis and Randolph write. "There currently are no carefully controlled data, however, to indicate a definitive association between sport-related concussion and increased risk for late-life cognitive and neuropsychiatric impairment of any form."
The authors say more rigorous and definitive studies are needed than the case reports and samples of convenience that have been done to date.
The study is titled "Modern Chronic Traumatic Encephalopathy in Retired Athletes: What is the Evidence?"
Randolph is a professor in the Department of Neurology of Loyola University Chicago Stritch School of Medicine.
Source: Loyola University Medical Center