Eccentric-focused rehabilitation promotes myelin plasticity in individuals with chronic, incomplete spinal cord injury

BackgroundMyelin plasticity has emerged as a novel mechanism by which the nervous system can change with experience, offering new potential for rehabilitation-induced recovery after neurotrauma. This first-in-human study investigated whether innovative, downhill locomotor rehabilitation promotes myelin plasticity in individuals with chronic, incomplete spinal cord injury (SCI). MethodsOf 20 individuals with SCI that enrolled, 4 passed the imaging screen and had myelin water imaging (MWI) before and after a 12-week (3 times/week) downhill locomotor treadmill training program (SCI+DH). One individual was excluded for imaging artifacts. Uninjured control participants (n=7) had two MWI sessions within the same day. Changes in myelin water fraction (MWF), a histopathologically-validated myelin biomarker, were analyzed in a priori motor learning and non-motor learning brain regions and the cervical spinal cord using statistical approaches appropriate for small sample sizes. ResultsWithin SCI+DH individuals, significantly more motor learning regions showed increased MWF than non-motor learning regions (p<.05). Compared to Control, MWF in the SCI+DH group increased in white matter underlying postcentral and precuneus cortices, combined motor learning brain regions, and ventral spinal cord (p<.05). To account for small sample size, an estimation-based approach showed the pattern of MWF increase was specific to training and region. ConclusionDownhill training increased MWF in brain regions specifically associated with motor learning and in the ventral spinal cord. Trial RegistrationClincialTrials.gov (NCT02498548, NCT02821845) FundingNational Institutes of Health [F31NS096921 (TDF), R21HD082808 (DMB)], Craig H. Neilsen Foundation [316282 (DMB)], Foundation for Physical Therapy Research [Promotion of Doctoral Studies Level II Scholarship (TDF)]