Evaluation of diffusion measurements reveals radial diffusivity indicative of microstructural damage following acute, mild traumatic brain injury.

PURPOSE:Mild TBI, characterized by microstructural damage, often undetectable on conventional imaging techniques, is a pervasive condition that disturbs brain function and can potentially result in long-term deficits. Deciphering the underlying microstructural damage in mild TBI is crucial for establishing a reliable diagnosis and enabling effective therapeutics. Efforts to capture this damage have been extensive, but results have been inconsistent and incomplete. METHODS:To that effect, we set out to examine the shape of the diffusion tensor in mild TBI during the acute phase of injury. We inspected diffusivity and geometric measurements describing the diffusion tensor's shape and compared mild TBI (N = 34, 20.4-66.6 yo) measurements with those from healthy control (N = 42, 20.7-67.2 yo) participants using voxelwise tract-based spatial statistics. Subsequently, to explore associations between the diffusion measurements in mild TBI, we performed nonparametric statistics and machine learning techniques. RESULTS:Overall, mild TBI displayed a diffuse increase in Dλ2, Dλ3, Dradial, Dmean, and Cspherical, with a diffuse decrease in Afractional, Amode, and Clinear, in addition to no change in Daxial or Cplanar. Most notably, our results provide evidence for Dradial as a potential biomarker for microstructural damage, specifically its main component Dλ2, based on their performance in discriminating between mild TBI and control groups. Afractional was also found to be important for discriminating between groups. CONCLUSION:Our results revealed the importance of a diffusion measurement often overlooked, Dradial, in assessing TBI and suggest differentiating diffusion measurements has the potential utility to detect variations in the underlying pathophysiology after injury.