Relationship Between Exercise Tolerance and Event-Related Potentials on Recovery in Adults with Postconcussion Syndrome

From the diagnosis and management through to determining recovery, the clinical pathway for concussions and postconcussion syndrome (PCS) is reliant on symptom reporting. Under-reporting or over-reporting bias necessitates the need for more objective measures. Exercise intolerance has shown to be a strong predictor of adolescent concussion patients likely to have protracted recoveries. Its role in predicting outcomes for adults is less clear. In addition to physiological measures, event-related potentials (ERPs) have demonstrated altered cognitive processing across the concussion recovery stages in various demographics. The aim of the present study was to assess the relationship between baseline exercise tolerance and ERPs on the degree of improvement in symptoms postrehabilitation in adults with persistent postconcussion symptoms (PPCS). Forty participants (mean age ± SD, 39 ± 13.5 years) with PPCS (mean duration ± SD, 5 ± 3 months) took part in this 6-week clinical trial. Participants were randomized at baseline to a customized rehabilitation (CR) program or standard, symptom-based care (SC). At baseline, participants underwent a standard exam inclusive of an exercise tolerance test and completed a quantitative electroencephalogram to examine three auditory ERPs (N100 for sensory processing, P300 for attention, and N400 for cognitive processing). To examine the association of exercise tolerance and ERPs on recovery, linear regression was done to compare participants' pre-post Rivermead Postconcussion Questionnaire scores (RPQ) with baseline delta heart rate (ΔHR), heart rate thresholds (HRt), and ERPs (amplitude and latency). The CR group showed significant and clinically meaningful improvements in reported symptoms (RPQ-3 and RPQ-13) and exercise tolerance (ΔHR, HRt). Notably, no baseline variables predicted outcomes in the CR group. Conversely, the SC group experienced no clinically meaningful symptom changes. For this group, baseline measures significantly correlated with symptom improvement. Exercise tolerance: Lower baseline ΔHR and HRt significantly correlated with less RPQ-3 (ΔHR: <i>p</i> = 0.01, <i>R</i>² = 0.28, coefficient = 0.03 || HRt: <i>p</i> = 0.006, <i>R</i>² = 0.36, coefficient = 0.04) and RPQ-13 improvement (ΔHR: <i>p</i> = 0.03, <i>R</i>² = 0.24, coefficient = 0.15 || HRt: <i>p</i> = 0.02, <i>R</i>² = 0.28, coefficient = 0.19). ERPs: Reduced N400 amplitude correlated with less improvement in RPQ-3 (RPQ-3: <i>p</i> = 0.05, <i>R</i>² = 0.19, coefficient = 0.55). Baseline exercise tolerance and ERPs were significant prognostic indicators for symptom improvement in adults with PPCS undergoing standard, symptom-based care. Participants with lower baseline exercise tolerance showed less improvement in postconcussion symptoms (RPQ-3 and RPQ-13), while reduced N400 amplitude was associated with poorer symptom outcomes. These baseline measures did not predict outcomes for patients receiving the customized rehabilitation program, suggesting that a comprehensive program may overcome initial physiological and cognitive vulnerabilities, leading to more robust recovery regardless of baseline presentation.