Comprehensive Locomotor Outcomes Correlate to Hyperacute Diffusion Tensor Measures After Spinal Cord Injury in the Adult Rat

In adult rats, locomotor deficits following a contusive thoracic spinal cord injury (SCI) are caused primarily by white matter loss/dysfunction at the epicenter. This loss/dysfunction decreases descending input from the brain and cervical spinal cord, and decreases ascending signals in long propriospinal, spinocerebellar and somatosensory pathways, among many others. Predicting the long-term functional consequences of a contusive injury acutely, without knowledge of the injury severity is difficult due to the temporary flaccid paralysis and loss of reflexes that accompanies spinal shock. It is now well known that recovery of high quality hindlimb stepping requires only 12-15% spared white matter at the epicenter, but that forelimb-hindlimb coordination and precision stepping (grid or horizontal ladder) requires substantially more trans-contusion communication. In order to translate our understanding of the neural substrates for functional recovery in the rat to the clinical arena, common outcome measures and imaging modalities are required. In the current study we furthered the exploration of one of these approaches, diffusion tensor magnetic resonance imaging (DTI), a technique now used commonly to image the brain in clinical research but rarely used diagnostically or prognostically for spinal cord injury. In the adult rat model of SCI, we found that hyper-acute (