REPORT FROM THE AMERICAN ACADEMY OF NEUROLOGY (AAN) ANNUAL MEETING, PHILADELPHIA PA, APRIL 26-MAY 3, 2014 – There has been a growing recognition in the U.S. of the problem of sports-related traumatic brain injury (TBI), notably in children and adolescents. An analysis of the U.S. National Electronic Injury Surveillance database found that the incidence of TBI-related Emergency Department visits increased 62% over a 10-year period, with 248,418 visits recorded in 2009 (Gilchrist J. MMR Weekly 2011;60:1337-1342). The estimated incidence of TBI visits was 298 per 100,000 population.
The highest TBI rates were seen in males aged 10-19 years. Long-term consequences of TBI include chronic traumatic encephalopathy, chronic post-concussion syndrome, chronic neurocognitive impairment, post-traumatic cognitive impairment or dementia, and post-traumatic parkinsonism.
While much attention has focused on football-related head injury, the most common cause of sports-related TBI is bicycling (football is number 2). Other higher risk activities are playing in a playground, basketball, soccer, horseback riding, ice skating, golf, all-terrain vehicle riding and tobogganing.
Several studies presented at AAN 2014 have examined TBI in professional athletes. A review of the hockey literature found that the most common CNS injuries were concussion (0.2-6.6 per 1000 player-hours), and spinal cord injuries (5.0 per 1000 player-hours) (Toy et al. AAN 2014; abstract P5.343). An analysis of blood biomarkers in 28 Swedish Hockey League players reported that levels of total-tau (T-tau, a marker of axonal injury) and S100 calcium binding B (S-100B, a marker of astroglial injury) were elevated versus pre-season values following a concussion (Shahim et al. AAN 2014; abstract S11.005). Biomarker concentrations peaked immediately after a concussion but decreased during rehabilitation.
A study of 26 retired National Football League players compared results on neuropsychological testing with functional imaging findings (Womack et al. AAN 2014; abstract I12-1.005). Delayed recall on verbal and visual memory testing was significantly correlated with abnormalities in the left perforant pathway and the inferior longitudinal fasciculus. The main finding was that grade 3 concussions were associated with decreased hippocampal volume, suggesting that the hippocampus is susceptible to damage during TBI events.
A separate study of retired NFL players found frontal lobe hyperactivation on fMRI, which was correlated with the self-reported number of concussions (Hubbard et al. AAN 2014; abstract I12-1.001). While subjects showed only modest deficits on tests of memory and planning, frontal lobe activation was notably pronounced when planning demands were increased.
Cumulative damage with frequent concussions was also seen in a study of 34 patients aged 10-50 years who were diagnosed with concussion (Shetty et al. AAN 2014; abstract P5.308). Overall, females had a longer recovery time than males (125 vs. 86 days), and all females had recovery times of at least two weeks. People who hit their head had longer recovery times than those with injuries resulting from a collision. Recovery time was significantly longer in people who read, or listened to audio books, talk radio or podcasts. Subjects with a history of a previous concussion had recovery times that were about four-fold longer than first-concussion patients.
To view the AAN’s current guidelines on the evaluation and management of concussion in sport, see Giza et al. Neurology 2013;80:2250-2257; free full text at www.neurology.org/content/80/24/2250.full).
Guest Reviewer: Dr. Daniel Selchen, Head of Neurology, St. Michael’s Hospital, Toronto, Canada