Diffusion Tensor Imaging Suggests Brain Compensation After Traumatic Injury
A special MRI technique may be able to predict which patients who have experienced concussions will improve, according to researchers. The results suggest that in some patients, the brain may change to compensate for the damage caused by the injury.
“This finding could lead to strategies for preventing and repairing the damage that accompanies traumatic brain injury [TBI],” said Michael Lipton, MD, PhD, Associate Director of the Gruss Magnetic Resonance Research Center at Albert Einstein College of Medicine of Yeshiva University and Medical Director of MRI Services at Montefiore Medical Center, both in Bronx, New York.
Each year, 1.7 million people in the United States sustain a TBI, according to the CDC. Concussions and other mild TBIs (or mTBIs) account for at least 75% of these injuries. Following a concussion, some patients experience a brief loss of consciousness. Other symptoms include headache, dizziness, memory loss, attention deficit, depression, and anxiety. Some of these conditions may persist for months or years in as many as 30% of patients.
The study involved 17 patients who were admitted to the emergency department at Montefiore and Jacobi Medical Centers and diagnosed with mTBI. Within two weeks of their injuries, the patients underwent diffusion tensor imaging (DTI), which reveals the movement of water molecules within and along axons. DTI allows researchers to measure the uniformity of water movement (fractional anisotropy) throughout the brain. Areas of low fractional anisotropy indicate axonal injury, and areas of abnormally high fractional anisotropy indicate changes in the brain.
“In a TBI, it’s not one specific area that is affected, but multiple areas of the brain that are interconnected by axons,” said Dr. Lipton. “Abnormally low fractional anisotropy within white matter has been correlated with cognitive impairment in concussion patients. We believe that high fractional anisotropy is evidence not of axonal injury, but of brain changes that are occurring in response to the trauma.”
One year after their brain injury, the patients completed two standard questionnaires to assess their postconcussion symptoms and evaluate their health status and quality of life. “Most TBI studies assess cognitive function, but it is not at all clear if and how well such measures assess real-life functioning,” said Dr. Lipton. “Our questionnaires asked about postconcussion symptoms and how those symptoms affected patients’ health and quality of life.”
After comparing the DTI data to the patient questionnaires, the researchers found that abnormally high fractional anisotropy predicted fewer postconcussion symptoms and better functioning. The results suggest that the brain may be actively compensating for its injuries in patients who exhibit areas of high fractional anisotropy on DTI.
“These results could lead to better treatment for concussion if we can find ways to enhance the brain’s compensatory mechanisms,” Dr. Lipton said.
Exercise Rate Related to Improvements in Parkinson’s Disease
People with Parkinson’s disease may benefit from exercise programs on stationary bicycles, and patients who pedal fastest may obtain the greatest benefit. Functional connectivity MRI (fcMRI) data showed that faster pedaling led to greater connectivity in brain areas associated with motor ability.
After Jay L. Alberts, PhD, a neuroscientist at the Cleveland Clinic Lerner Research Institute, rode a tandem bicycle across Iowa with a patient with Parkinson’s disease, the patient experienced improvements in her symptoms.
“The finding was serendipitous,” said Dr. Alberts. “I was pedaling faster than she was, which forced her to pedal faster. She had improvements in her upper extremity function, so we started to look at the possible mechanism behind this improved function.”
As part of this inquiry, Dr. Alberts, researcher Chintan Shah, BS, and their Cleveland Clinic colleagues used fcMRI to study the effect of exercise on 26 patients with Parkinson’s disease.
“By measuring changes in blood oxygenation levels in the brain, fcMRI allows us to look at the functional connectivity between different brain regions,” said Mr. Shah.
The patients underwent bicycle exercise sessions three times per week for eight weeks. Some patients exercised at a voluntary level, and others underwent forced-rate exercise, pedaling at a speed above their voluntary rate. The researchers induced forced-rate activity with a modified exercise bike.
“We developed an algorithm to control a motor on the bike and used a controller to sense the patient’s rate of exertion and adjust the motor based on his or her input,” said Dr. Alberts.
The researchers conducted fcMRI before and after the eight weeks of exercise therapy and again as follow-up four weeks later. The team calculated brain activation and connectivity levels from the fcMRI results and correlated the data with average pedaling rate. Results showed increases in task-related connectivity between the primary motor cortex and the posterior region of the thalamus. Faster pedaling rate was the key factor related to these improvements, which were still evident at follow-up.