Effects of Multiple Sports Related Concussions On Neurocognition and Cerebral Vascular Function

Abstract

PURPOSE: To determine the differences in neurocognition (NC) and cerebral vascular reactivity (CVR) between athletes with multiple sports related concussions (mTBI) and matched controls (C). METHODS: Twelve athletes (22±0.5 y SEM) who reported multiple sports related concussions (≥3) and 12 matched [age, sex, body mass index (BMI), and athletic status] healthy concussion free controls (23±0.5 y) were recruited. Neurocognitive methods Each participant completed neurocognitive testing (NC) including WASI II, HVLT R, Grooved Pegboard, DKEFS, Connors’ CPT test II, WAIS-IV subsets, and BRIEF. CVR methods Participants were fitted with a custom breathing circuit attached to a computer-controlled gas-blending device to evaluate baseline end-tidal carbon dioxide (PetCO2). To alter brain blood flow a PetCO2 gas challenge, which consisted of two square wave increases of 10 mmHg above baseline PetCO2 and a ramp protocol that decreased PetCO2 to 32 mmHg and then increased linearly to 50 mmHg over a 7 min. period was utilized while PetO2 was maintained at 100 mmHg. Each participant underwent brain imaging using a 3T MRI for concurrent structural and functional (BOLD) imaging. CVR (% BOLD signal change/mmHg CO2) was computed by using a robust linear least squares fit to the correlation between the two time courses. RESULTS: As expected mTBI and C were similar in age (22±1 vs. 23±1 y, P=0.07), height (173±3 vs. 174±3 cm, P = 0.76), weight (76±6 vs. 80±6 kg, P=0.37) and BMI (24±1 vs. 26±1 kg/m2, P=0.18). Baseline PetCO2 (38±1 vs. 36±1 mmHg, P=0.44) was not significantly different. Whole brain gray matter CVR was also not significantly different in mTBI vs. C groups for the full sequence (0.380 ± 0.014 vs. 0.379 ± 0.014 %BOLD/mmHg, P=0.94), squares waves only (0.380 ±0.017 vs. 0.390±0.017, P=0.68) and ramp only (0.377±0.013 vs. 0.375±0.013, P=0.92). Differences in NC testing (mTBI vs. C) were DKEFS Trail Making-motor speed (11.4±0.3 vs.12.5±0.3, P=0.02); DKEFS Color Word Inference inhibition (13.0 ± 0.4 vs. 11.8 ± 0.4, P=0.05); and Conners’ CPT Test II Commission (%) (58.2±2.8 vs. 51.4±2.8, P=0.04). CONCLUSIONS: The data from this study suggest that multiple sports related concussions do not have long-term effects on CVR, however NC data showed reduced reaction time and attention. Supported by National Football League Charities