The first prospective evidence suggesting that concussion is associated with reduced cerebral blood flow, which recovers in most individuals within a few weeks, has been reported from a new study.
The authors suggest that if these results can be confirmed and expanded in further studies, they could have important implications for the management of concussion and cerebral blood flow may become an objective biomarker for the condition.
"While it's too early for these observations to have any immediate impact on clinical practice, they could be a first step towards developing an objective biological based biomarker which can predict concussion and help determine when it is safe to return to play," lead author, Timothy B. Meier, PhD, The Mind Research Network, Albuquerque, New Mexico, commented to Medscape Medical News.
He explained that the symptoms of concussion appear to subside before the brain has fully recovered.
"In our study, self-reported symptoms had all recovered by 1 week. Mood symptoms, which are an understudied area, may take a bit longer but still are usually recovered by 1 month," he said. "But in some patients, blood flow does not appear to have completely recovered by 1 month, and those with lower blood flows at 1 month had worse outcomes in terms of earlier clinical symptoms. So this could be a real-world independent measure."
Their findings were published online in JAMA Neurology on March 2.
"A Real-World Independent Measure"
The current study involved 17 collegiate football athletes with concussions diagnosed at the time of head injury by physicians trained in sports medicine.
Dr Meier and colleagues then used MRI to assess cerebral blood flow in these individuals at 1 day, 1 week, and 1 month after concussion, and these observations were compared with similar measurements from a control group of 27 nonconcussed football athletes matched for age. Neuropsychiatric evaluations and a brief cognitive screen were also performed at all three time points.
Clinicians trained in sports medicine also provided an independent measure of concussion outcome: the number of days withheld from competition.
Results showed that cognitive (simple reaction time) and/or neuropsychiatric symptoms were present at 1 day but that the cognitive symptoms had resolved by 1 week and the neuropsychiatric symptoms had resolved by 1 month after injury.
Imaging data showed that cerebral blood flow in the right superior temporal sulcus and the right dorsal midinsular cortex was significantly reduced at 1 day and 1 week after injury compared with the control athletes, but cerebral blood flow in the concussed individuals improved over time. By 1 month there were no differences between the two groups.
Blood Flow Inversely Related to Symptoms
However, cerebral blood flow in the dorsal midinsular cortex was still reduced at 1 month after concussion in athletes deemed slower to recover by the sports medicine physicians. Cerebral blood flow in this region in these individuals was also inversely related to the magnitude of initial psychiatric symptoms, suggesting a potential prognostic indication for cerebral blood flow as a biomarker, the researchers report.
They note that most of the 3.8 million sports-related traumatic brain injuries that occur annually are concussions. Because of the high incidence and potentially deleterious consequences of repeat injury, it is imperative that methods for accurately and objectively diagnosing the presence and severity of concussions are developed.
They conclude: "The resolution of cerebral blood flow abnormalities closely mirrors previous reports from the animal literature and show real-world validity for predicting outcome following concussion….Thus, the current results suggest that regional cerebral blood flow may provide an objective biomarker for tracking both normal and potentially pathological recovery from concussion."
Noting that "second-impact syndrome" is believed to result from autodysregulation of intracranial and cerebral perfusion pressures following concussion, they suggest that the development of objective biomarkers to measure cerebral blood flow recovery after concussion may have clinical use for reducing this rare but fatal disorder.
The researchers are now involved in a larger study in which all first-division athletes in Albuquerque undergo head scanning at the start and end of the season, as well as at multiple time points after a head injury, which will provide additional information.
This research was conducted using internal funds from the Laureate Institute for Brain Research, which is supported by The William K. Warren Foundation. The authors have disclosed no relevant financial relationships.
JAMA Neurol. Published online March 2, 2015. Abstract
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Cite this: Cerebral Blood Flow: A Biomarker for Concussion? - Medscape - Mar 06, 2015.