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Diffusion Tensor Imaging Identifies New Biomarker of One-Year Outcomes after Mild TBI

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A DTI scan of the brain of a patient with mild traumatic brain injury showing areas with low fractional anisotropy (FA) (red) and high FA (blue).​

Photo reproduced from Strauss SB, Kim N, Branch CA. Bidirectional Changes in Anisotropy Are Associated with Outcomes in Mild Traumatic Brain Injury. AJNR Am J Neuroradiol 2016 Jun 9.

BY SARAH OWENS

Brain abnormalities detected on diffusion tensor imaging (DTI), a magnetic resonance imaging technique, helped predict the recovery outcomes of patients with mild traumatic brain injury (mTBI) one year later, according to a new study published online ahead of print on June 9 in The American Journal of Neuroradiology.

For the study, emergency department physicians at Montefiore Medical Center performed DTI scans of 39 patients diagnosed with mTBI within 16 days of the injury, as well as healthy controls. The researchers found that the scans of those with mTBI, compared with controls, showed two distinct types of white matter damage: areas of abnormally high fractional anisotropy (FA) — the uniformity of water molecules detected on DTI — or abnormally low FA.

Follow-up assessments with 26 patients one year later found that those whose DTI scans showed abnormally high FA had better outcomes on tests of cognition and post-concussion symptoms. Study subjects who had high FA in the left frontal lobe and left temporal lobe performed better on tests of attention and those who had high FA in the right thalamus experienced fewer emotional post-concussion symptoms, for example.

These outcomes, the study authors concluded, suggest that DTI imaging analyses of high FA in specific brain areas may be a good predictor of functional outcomes at one year after mild TBI.

"While we still lack effective treatments, we now have a better understanding of the neurological mechanisms that underlie a favorable response to concussion," said study leader Michael L. Lipton, MD, PhD, professor of radiology, of psychiatry and behavioral sciences, and of neuroscience at Albert Einstein College of Medicine, in a press release accompanying the study. "[This] opens a new window on how to look at therapies and to measure their effectiveness."

Noting that previous imaging studies of outcomes after mTBI did not have the ability to recognize spatial variation in the location of the injury — a principal feature of mild TBI — researchers used an individualized approach to assess the spatial heterogeneity of traumatic axonal injury in the study participants, called the Enhanced Z score Microstructural Assessment of Pathology, or EZ-MAP. The EZ-MAP, unlike other tools that measure damage caused by TBI, can delineate abnormal brain regions that relate to particular cognitive functions in individual patients.

The researchers noted that more studies are needed to validate the approach. "While were able to predict the outcomes for the patients in our study, more refined approaches — incorporating additional patient and injury characteristics, for example — may be needed when applying the test on widely differing individuals," Dr. Lipton said.