Abstract
Neuroimaging has identified significant disturbances in cerebrovascular reactivity (CVR) in the early symptomatic phase of sport-related concussion. However, less is known about how whole-brain alterations in CVR evolve after concussion and whether they remain present beyond medical clearance to return to play (RTP). In the present study, CVR was evaluated using blood-oxygenation-level-dependent functional magnetic resonance imaging (BOLD fMRI) during a respiratory challenge. Imaging data were collected for 110 university-level athletes, including 39 concussed athletes and 71 athletic controls. The concussed athletes were imaged at the acute phase of injury (1–7 days post-injury), the subacute phase (8-14 days post-injury), medical clearance to RTP, 1 month post-RTP, and 1 year post-RTP. Enhanced negative BOLD response to controlled breathing was seen at acute injury, with attenuation of the effect mainly occurring by 1 year post-RTP. Secondary analyses showed that greater symptom severity and prolonged recovery were associated with enhanced BOLD response in the acute phase of injury, but a more attenuated BOLD response in the subacute phase. This study provides novel information characterizing the CVR response after concussion and shows CVR to be a sensitive technique for evaluating long-term brain recovery.
Highlights
Concussion is a form of mild traumatic brain injury (TBI) that manifests as functional disturbances, usually in the absence of overt radiological findings
None of the concussed athletes in this study had acquired a new concussion between acute phase of injury (ACU) and 1 year post-RTP (1YR) imaging sessions, and all athletes had returned to normal school and/or work, social, and sport activities following return to play (RTP)
The BOLD response was similar to previous studies [12, 17, 21], with progressively more negative signal during the controlled breathing (CB) phase, followed by a plateau and subsequent return to baseline during breath holding (BH) and normal breathing (NB) phases
Summary
Concussion is a form of mild traumatic brain injury (TBI) that manifests as functional disturbances, usually in the absence of overt radiological findings. The diagnosis and management of sport-related concussion is based on symptom status, along with brief evaluations of cognition and balance. Based on international consensus guidelines [1], the medical clearance to return to play (RTP) is determined by symptom resolution, following the completion of a graded exercise protocol. The physiological mechanisms that underlie post-concussion impairments remain incompletely understood [2]. It is presently unclear which physiological changes have dissipated at the time of RTP and which ones persist beyond medical clearance.
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