Pathophysiology of spasticity

Spasticity arises from lesions involving the corticoreticulospinal system in the brain, brainstem or spinal cord. Abnormal suprasegmental influences lead to increased spinal cord excitability and to impairment of interneuronal systems thereby giving rise to increased muscle tone, enhanced stretch reflexes, muscle overactivity and antagonist muscle co-contraction. Additionally, muscle paresis and immobilisation in a shortened position result over time in structural changes that involve muscles, joint, tendons and bones and contribute to muscle stiffness. Spasticity is a complex motor disorder that arises from a central nervous system dysfunction and causes changes at all locomotor system levels, from the cerebral cortex to muscles, joints and bone.