Mechanisms of Different Motor Neurons in the Occurrence of Spasticity After Spinal Cord Injury: A Narrative Review

Spasticity is a common complication after spinal cord injury (SCI) that significantly diminishes quality of life and complicates daily management. As a hallmark of upper motor neuron lesions, spasticity emerges through a complex post-injury process involving the resolution of spinal shock, an imbalance between excitatory and inhibitory signaling, and maladaptive neuronal plasticity, leading to hyperreflexia and chronic spasticity. Severe spasticity frequently results in pain, sleep disturbances, and marked functional impairments. This review systematically integrates motor neuron alterations with corresponding muscle manifestations, providing a comprehensive analysis of the brain-spinal cord-muscle pathway in spasticity pathogenesis. Through an in-depth analysis of the pathological and physiological changes in motor neurons post-SCI, this review offers a novel perspective that unveils the intrinsic mechanisms underlying spasticity formation, thereby establishing a robust theoretical foundation for developing targeted therapeutic strategies.