Abstract 2: Structural Integrity of the Corpus Callosum Correlates with Sensorimotor Impairment after Stroke

Introduction: Responsiveness to motor rehabilitation varies greatly after stroke. Improved knowledge of the brain correlates of motor function are needed to assist in the development of more effective and personalized rehabilitation protocols. Changes in the integrity of the ipsilesional corticospinal tract after stroke have been well documented, but less is known about changes in the corpus callosum (CC). The purpose of this study was to determine if structural integrity of the motor and sensory portions of the CC change after stroke and whether any such changes are related to clinical measures of sensorimotor impairment and function. Methods: Fifty-five individuals with chronic stroke (age 60.5±13.2; days post-stroke 351.9±560; UE Fugl-Meyer (FM) motor score 38.5±14.6, no lesion in the CC) and 16 age-matched controls underwent diffusion tensor imaging (DTI) and behavioral assessments. Mean fractional anisotropy (FA) values for the motor and sensory regions of the CC were extracted and examined in relation to motor system behavioral measures including the UEFM, Box & Blocks (BB), Nottingham sensory score, and Stroke Impact Scale (SIS) hand subsection. Results: Participants with stroke had significantly lower FA values compared to controls in both the motor and sensory CC regions ( p <0.02) despite their strokes sparing the CC. In the CC motor region, FA was related to UEFM, BB, and SIS scores, such that higher structural integrity correlated with better motor status ( ρ >0.30, p <0.03 across comparisons). In the CC sensory region, FA was related to UEFM and SIS scores ( ρ >0.31, p <0.02) as well as Nottingham sensory scores (ρ=0.33, p<0.05). CC motor and sensory FA did not correlate with FA in the ipsilesional peduncle ( ρ <0.12, p >0.40), suggesting that the magnitude of change in each region of the motor system was distinct. Conclusions: Decreased structural connectivity between the sensorimotor regions of the two hemispheres is related to motor impairment in chronic stroke in a manner that is distinct from corticospinal tract injury. Interventions that target the communication between hemispheres during motor rehabilitation may be warranted.