Spasticity is most commonly associated with which type of lesion?

Spasticity is most commonly associated with which type of lesion?

• A. Upper motor neuron lesions
• B. Lower motor neuron lesions
• C. Peripheral neuropathy
• D. Muscular dystrophy

Answer: (A)

Spasticity comes from loss of inhibitory control that brain pathways normally exert over the spinal stretch reflex. When upper motor neurons are damaged, the spinal circuits become hyperexcitable, so quick stretches provoke a stronger resistance and reflexes are exaggerated. This velocity-dependent tone increase, often with hyperreflexia and sometimes clonus, is a hallmark of upper motor neuron lesions—seen after stroke, traumatic brain injury, spinal cord injury above the reflex arc, or multiple sclerosis. In contrast, lower motor neuron lesions tend to produce flaccidity with reduced tone and reflexes, while peripheral neuropathies and muscular dystrophy usually cause weakness and atrophy without the characteristic spastic, velocity-dependent tone.

Spasticity comes from loss of inhibitory control that brain pathways normally exert over the spinal stretch reflex. When upper motor neurons are damaged, the spinal circuits become hyperexcitable, so quick stretches provoke a stronger resistance and reflexes are exaggerated. This velocity-dependent tone increase, often with hyperreflexia and sometimes clonus, is a hallmark of upper motor neuron lesions—seen after stroke, traumatic brain injury, spinal cord injury above the reflex arc, or multiple sclerosis. In contrast, lower motor neuron lesions tend to produce flaccidity with reduced tone and reflexes, while peripheral neuropathies and muscular dystrophy usually cause weakness and atrophy without the characteristic spastic, velocity-dependent tone.