Cerebral blood flow reduced after concussion

By Anne Harding

Cerebral blood flow (CBF) is reduced in athletes following a concussion, according to the first-ever longitudinal study to look at changes in regional CBF in humans after concussion.

Blood flow in the dorsal midinsular cortex (dmIC) remained low at one month post-concussion in the athletes who took longer to recover, Dr. Timothy Meier of The Mind Research Network/Lovelace Biomedical and Environmental Research Institute in Albuquerque, New Mexico, and his colleagues found.

They also found reduced dmIC CBF was also associated with worse initial psychiatric symptoms. They report the findings online March 2 in JAMA Neurology.

While the findings are "encouraging" and suggest CBF could one day be used as a biomarker for concussion prognosis, Dr. Meier told Reuters Health in a telephone interview, "we're a ways away from realizing the full potential of CBF in the clinical setting." For one thing, he noted, the arterial spin labeling magnetic resonance imaging (MRI) used in the study is expensive and not widely available.

Studies in animals have shown reduced CBF after concussion, Dr. Meier and his colleagues write, and has also been shown in human traumatic brain injury (TBI). However, they note, most studies in humans have focused on individuals with chronic symptoms of TBI, who represent a small minority of concussion patients.

In the new study, the researchers recruited 44 collegiate football players, 17 of whom sustained concussions. The concussed athletes underwent neuropsychological testing and arterial spin labeling MRI at one day, one week, and one month after they were injured, while the healthy controls had the tests at a single time point. Injured athletes were classified as having poor outcomes if they were withheld from competition for longer than 14 days.

Average Hamilton Anxiety (HAM-A) and Hamilton Depression (HAM-D) scores were higher in the injured athletes one day after their injury than in the healthy athletes, but recovered over time. HAM-D scores remained higher than those in the normal athletes at each time point, while HAM-A scores were higher at one day and one week after injury, and trended higher at one month post-injury.

CBF in the dmIC and the right superior temporal sulcus were lower at time 1 and time 2 than at time 3 in the injured athletes. By time 3, CBF in both areas did not differ significantly for the injured athletes versus healthy controls.

However, the athletes who had poor outcomes had lower dmIC CBF at time 3 than the athletes who had good outcomes. The athletes with worse outcomes also had significantly higher average HAM-A and HAM-D scores at time 1 than those with good outcomes. Scores were also higher for the athletes with worse outcomes at visits 2 and 3, although the difference was not significant.

"The current results suggest that regional CBF may provide an objective biomarker for tracking both normal and potentially pathological recovery from concussion," Dr. Meier and colleagues write.

"The dmIC belongs to a middle-posterior insular network that has been associated with visceral (ie, autonomic) input (eg, pain) and plays a role as a general salience and action system and participates in functions of body orientation and response selection," they add. "Common concussion symptoms, including balance problems, dizziness, and reduced reaction times, could possibly be related to the disruption of this network."

Dr. Meier said he and his colleagues are now planning a study in which they would perform brain scans in all Division 1 athletes in the Albuquerque area at the start of the season and the end of the season, as well as in any athletes who sustain concussions. "We're trying to grow this program to the high school level as well," he added. "There's definitely a lot of remaining questions."

The study was funded with a grant from the Laureate Institute for Brain Research, which is supported by The William K. Warren Foundation. The authors report no conflicts of interest.

SOURCE: http://bit.ly/1wExTu5

JAMA Neurol 2015.

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