How mental fatigue influences neurovascular coupling in post-concussion syndrome : a preliminary pilot study

Introduction: Although most concussions have symptoms only lasting a few days, some leave impact for months or more, becoming post-concussion syndrome (PCS). With PCS, there can be reduced capacity of mental processes, this is called mental fatigue. It is unknown how mental fatigue manifests in the brain, which limits treatment to those affected. It is possible that the relationship between neural activation and blood flow could provide insight. Methods: 4 participants completed a questionnaire on their concussion history and symptoms. They then completed a self-report survey on how mentally fatigued they felt, as well completing a transcranial Doppler (ultrasound) measure of the middle cerebral artery (MCA) and posterior cerebral artery (PCA) response to stimuli in and simple reaction time (SRT) before and after a 45-60-minute task designed to induce mental fatigue. Results: It was found that changes in mental fatigue questionnaire responses had a strong, positive correlation with both number of PCS symptoms (R=0.99) and symptom severity (R=0.94). Higher levels of mental fatigue were strongly associated with lower time to cerebral blood flow (CBF) peak (PCA=-0.75, MCA=-0.72) and lower increases in CBF from rest to peak stimulation (PCA=-0.67, MCA=-0.56). Higher changes in mental fatigue were strongly associated with worse SRT in both a visual task (R=0.52) and an auditory task (0.98). Discussion: These preliminary data are the first to indicate a physiological manifestation of mental fatigue as a PCS symptom, improving our understanding of the symptom. Interventions for physiological symptoms could be adapted to improve PCS-based mental fatigue.Health and Social Development, Faculty of (Okanagan)Health and Exercise Sciences, School of (Okanagan)Graduat