Sangari S, et al. - Researchers studied the impact of residual descending motor pathways on spasticity in humans with spinal cord injury (SCI) using neurophysiological and imaging techniques. Without preserving voluntary motor output in the quadriceps femoris muscle, spasticity was measured in 33 people with motor complete SCI. Investigators observed that 60% of participants showed spasticity symptoms while the other 40% showed none, signifying the existence of two clear human subgroups with motor complete SCI. Motor evoked potentials (MEPs) were only seen in people with spasticity and MEP size associated with spasticity severity. In non-spastic patients, spinal cord atrophy was greater vs spastic patients. In the lateral regions of the spinal cord, the degree of spared tissue was positively linked with the severity of spasticity, signifying the preservation of white matter associated with motor tracts when spasticity was present. The theory that preserving descending motor pathways impact spasticity in humans with motor complete SCI was supported, which may help rehabilitate and evaluate people with SCI.