Chronic Traumatic Encephalopathy in a Neurodegenerative Disorders Brain Bank
Bieniek KF., Ross OA., Cormier KA., Walton RL., Soto-Ortolaza A., Johnston AE., DeSaro P., Boylan KV., Graff-Radford NR., Wszolek ZW., Rademakers R., Boeve BF., McKee AC., Dickson DW. Acta Neuropathol 2015; 130:877-889.
Take Home Message: CTE pathology was only detected in individuals with documented participation in contact sports.
Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disorder, where the onset is linked with a variety of contact sports. In the past 26 years, over 160 million people participated in high school or collegiate sports; however, the proportion of this cohort at risk for developing CTE is unknown. Therefore, the authors conducted a retrospective cohort study to screen for CTE among individuals with and without a history of contact sports. Over 1,700 brains without known neuropathologic conditions were received from a brain bank for neurodegenerative disorders. The authors collected clinical and demographic data (type of sport, medical family history, age at death, exposure to non sports-related head impacts) from available medical records and obituaries. Brain tissue was assessed for neuropathologic conditions (tau pathology) by immunohistochemistry, and brain tissue samples were collected to determine genetic association (3 genes; MAPT, TMEM106B, APOE) to CTE. Sixty-six patients (54 males, 65 Caucasian) participated in a contact sport (34 football, 8 boxers, 7 baseball, 1 basketball, 1 ice hockey, 1 soccer, 1 rodeo, 1 martial artist). The authors matched every athlete with two people that had no history of contact sports. Additionally, 66 females were included as controls. Within the control group, 33 individuals had a history of head trauma (14 falls, 10 motor vehicle accidents, 4 violent assaults, 4 domestic abuse, and 2 unspecified head incidents). The immunohistochemistry results found 32% of those that participated in contact sport had tau pathology consistent with CTE. Of the 43 patients that participated in football, 16 had CTE pathology, where 6 played up to high school, 7 played up to college, and 1 played professionally. Among the 27 former football players with no observed CTE pathology, 15 played up to high school, and 7 played up to college. No CTE pathology was observed in the control group. The authors found no differences between clinical or demographic data between patients with/without exposure to contact sports and CTE pathology. The authors also did not identify any genetic associations to CTE.
This study has important implications for the public health given the number of people that participate in contact sports. The results of this study suggest that individuals that participate in contact sports are at a higher risk for having CTE compared to those that do not participate in contact sports. It was interesting to note that the authors did not observe any CTE pathologies in the control group, including those that had previous head trauma. This suggests that CTE may be related to repetitive impacts, and a single blow is not likely going to initiate CTE. The authors did not find any genetic association to CTE but they also found no clinical or demographic differences between those with and without CTE that participated in contact sports; hence, genetic association to CTE should not be discounted. This research should be continued in a larger, prospective cohort that includes more females and other races due to the current cohort of contact sport cases were predominantly white males. Furthermore, future studies should try to recruit individuals that are reflective of the general population of athletes and nonathletes rather than relying on a brain bank that focuses on neurodegenerative disorders. This will help clarify the true risk of CTE among athletes in contact sports. It will also be interesting to see future research verify that individuals who do the assessments are unaware which specimens came from athletes and nonathletes. In the meantime, medical professionals need to be aware of these findings and educate patients on the possible long-term consequences of repetitive head impacts during contact sport participation.
Questions for Discussion: Do you address CTE pathology when you educate parents, coaches, and athletes about concussions? Do you believe there would be an increased risk of CTE pathology in athletes that start contact sport in middle school or younger youth leagues?
Written by: Jane McDevitt, PhD
Reviewed by: Jeff Driban