Cerebral blood flow recovery could be a biomarker of outcomes in athletes following concussion, according to an imaging study published online ahead of print March 2 in JAMA Neurology. “To our knowledge, this study provides the first prospective evidence of reduced cerebral blood flow and subsequent recovery following concussion in a homogeneous sample of collegiate football athletes and also demonstrates the potential of quantified cerebral blood flow as an objective biomarker for concussion,” said lead author Timothy B. Meier, PhD, and his research colleagues. According to the investigators, the resolution of cerebral blood flow abnormalities closely mirrors that of previous reports from the animal literature and shows real-world validity for predicting outcome following concussion.
Timothy B. Meier, PhD
Dr. Meier, of the Mind Research Network/Lovelace Biomedical and Environmental Research Institute in Albuquerque, and colleagues enrolled 44 collegiate football athletes in a mixed longitudinal and cross-sectional study at a private research institute specializing in neuroimaging. The study was conducted from March 2012 to December 2013.
Of the 44 football players, 17 were concussed and had serial imaging performed approximately one day, one week, and one month postconcussion. The study also included 27 healthy football players who served as a control group. All athletes reported no premorbid mood disorders, anxiety disorders, substance abuse, or alcohol abuse.
Arterial spin labeling MRI was used to collect voxelwise relative cerebral blood flow data at each visit. Neuropsychiatric evaluations and a brief cognitive screen also were performed at all three time points (ie, one day, one week, and one month). Clinicians trained in sports medicine provided an independent measure of real-world concussion outcome (ie, number of days withheld from competition).
Cognitive (ie, simple reaction time) and neuropsychiatric symptoms at one day postconcussion resolved at either one week postinjury or one month postinjury. Imaging data suggested cross-sectional (ie, healthy vs concussed athletes) and longitudinal (ie, one day and one week vs one month postinjury) evidence of cerebral blood flow recovery in the right insular and superior temporal cortex. The researchers also found that cerebral blood flow in the dorsal midinsular cortex was decreased at one month postinjury in slower-to-recover athletes and was inversely related to the magnitude of initial psychiatric symptoms, as rated on the Hamilton Depression Scale and the Hamilton Anxiety Scale.
“The current results suggest that regional cerebral blood flow may provide an objective biomarker for tracking both normal and potentially pathologic recovery from concussion,” the researchers concluded.
Future studies identifying the time course of metabolic dysfunction following concussion and its relationship to cerebral blood flow are crucial to characterize the physiologic effect of concussion, according to the investigators. “Specifically, the cerebral metabolic rate of glucose, the cerebral metabolic rate of oxygen, and cerebral blood flow are tightly coupled in health, but become dysregulated following mild traumatic brain injury.”
—Glenn S. Williams