Brain lesions in players of contact sports

Abstract

It is well known that boxing causes brain damage, but the hazards for the brain of some popular contact games, such as American football or soccer, have not been investigated by modern imaging. We studied 15 male amateur soccer players (aged from 18 to 34 years) and 17 male American football players (from 18 to 36 years) by magnetic resonance imaging (MRI) (1·0 T); 20 age-matched and sex-matched non-athletes served as controls. The imaging and analysing methods have been described in detail previously. All men were examined carefully and were healthy at the time of the MRI. One soccer player having drug treatment for hypothyroidism and one American football player had medication for high blood pressure. Smoking and drinking habits did not differ between the groups. Because of the many orthopaedic operations undergone, some players had been anaesthetised several times (seven soccer and five American football players). Eight players had had head traumas and unconsciousness at least once. One soccer player had had a subdural haematoma which had been operated on. All players had trained more than five times weekly for many years and played in men’s elite series for 1–15 years. On MRI, 11 soccer players, seven American football players, and five controls had high-signal foci in the white matter on T2-weighted images; range (mean and median) of these foci were 1–39 (12 and 5), 2–15 (7 and 6), and 1–15 (5 and 4), respectively. 79% of these high-signal foci, which could not be found on proton density-weighted images, are thought to represent enlarged perivascular spaces, a sign of axonal rarefaction in the white matter, or non-ischaemic demyelination associated with subependymal gliosis. However, eight soccer players, three American football players, and two non-athletic controls had from one to nine high-signal foci both on T2-weighted images and on proton density-weighted images, suggesting instead microinfarcts or ischaemic tissue damage. The size of these foci was under 5 mm in all cases. The number of foci did not correlate with age nor with years of active play. The clinical significance of incidental white-matter foci is controversial. However, quite recently these foci in healthy individuals have been found to be correlated with subtle cognitive dysfunction. But why do soccer players have such foci so much more frequently than American football players and non-athletes? Today American football players wear helmets. We believe that the foci in the brain seen in soccer players may be due to minor brain traumas sustained during the game.