Controlled aerobic exercise rehabilitation may help relieve symptoms that patients with post-concussion syndrome experience with exercise and after prolonged cognitive working memory tasks by restoring normal cerebral blood flow regulation, finds an important new study.
The conventional wisdom has been that PCS should be treated with rest, reassurance and anti-depressants, and that physical activity should be avoided, but emerging research suggests that controlled exercise rehabilitation may be a core component of treatment of children, adolescents, and young adults who are slow to recover from concussion.
In a landmark 2010 study, researchers at the State University of New York-Buffalo (SUNY-Buffalo) showed that exercise assessment and aerobic exercise training may reduce symptoms PCS patients experience during prolonged cognitive working memory tasks, such as fatigue and difficulty concentrating.
The reason they believed a controlled, graded, symptom-free exercise protocol worked was because it restored the regulatory system responsible for maintaining cerebral blood flow, which may be dysfunctional in people with concussion.
"The data suggest that some PCS symptoms are related to disturbed cerebral autoregulation, and that after this treatment, the brain was able to regulate blood flow when the blood pressure rose during exercise," said John J. Leddy, MD, Associate Professor of Orthopaedics and Co-Director of the Sports Medicine Clinic at SUNY-Buffalo, and lead author of the study. "We think progressive stepwise aerobic training may improve cerebral autoregulation by conditioning the brain to gradually adapt to repetitive mild elevations of systolic blood pressure."
To test their theory, Leddy and his colleagues used a form of functional magnetic resonance imaging (fMRI) called blood oxygenation level dependent (BOLD) imaging. By measuring differences in the magnetic properties of oxygenated versus deoxygenated blood, it indirectly indicates changes in cerebral blood flow to areas of increased brain activity. They recruited 10 patients diagnosed with PCS who experienced exacerbation of concussion symptoms on a progressive exercise test and had been symptomatic for 6 weeks or more but 12 months or less along, along with 10 healthy controls.
After completing a baseline fMRI and an exercise treadmill test, five PCS patients were randomly assigned to perform a controlled and progressive aerobic exercise program in which they exercised for 20 minutes a day, 6 days a week, for 12 weeks, either on a treadmill at home or in a gym, at 80% of the heart rate at which their concussion symptoms were exacerbated. Their programs were individually modified as the heart rate provoking symptoms increased. When they were able to exercise up to age-predicted maximum heart rate without symptoms returning, the group then underwent a second fMRI scan.
The other five PCS patients were assigned to a standardized 12-week program involving 20 minutes per day, six days a week of low-impact breathing and stretching (e.g. quadriceps, double or single knee to chest, sitting hamstring, etc.) and instructed not to exceed a low target heart rate of 40%-50% of age predicted maximum heart rate so as not to affect cardiovascular fitness. They underwent a baseline fMRI scan and again at approximately 12 weeks.
At baseline, the researchers found that the PCS patients had reduced exercise capacity, more fatigue and other symptoms, and showed activations in areas of the brain on performing a math processing test during an fMRI not used by the healthy controls, who also had significantly greater brain activation during the math test.
When tested again after 12 weeks, the PCS exercise group achieved significantly greater exercise heart rate and had fewer symptoms, and their fMRIs did not differ from healthy controls, while the PCS stretching group still had significantly less activity in several areas of the brain. Cognitive performance did not differ by group or time.
"Before exercise treatment, the 2 PCS groups combined were different from healthy controls but not from each other. After treatment, the exercise group was not different from healthy controls whereas the placebo group showed several regional differences from healthy controls and showed a small regional difference approaching significance when compared with the exercise group," wrote Leddy.
"Controlled exercise treatment may therefore help to restore normal local CBF regulation, as least as reflected by fMRI BOLD activation patterns, during a cognitive test," he said.
Leddy and his colleagues speculated that the "same physiologic dysfunctions, problem with CBF regulation, and autonomic imbalance that are associated with exacerbation of symptoms during exercise are also responsible for the symptoms PCS patients experience during prolonged cognitive working memory tests, such as fatigue and difficulty concentrating," citing earlier studies reporting abnormal activations during working memory tasks after mild traumatic brain injury.[5-10]
The pilot study sets the stage for a randomized study with a larger sample in order to correlate symptoms and cognitive performance with fMRI results.
"Although the number of participants is extremely small, the results are statistically significant and the overall experimental design is good, said Dave Ellemberg, PhD, Professor in the Department of Kinesiology at the University of Montreal, who was not involved in the study. "I think that this approach is promising, and am convinced that the future of concussion rehabilitation is through exercise."
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