Which BEST defines spasticity as it relates to spinal cord injury?

Which BEST defines spasticity as it relates to spinal cord injury?

• A. A constant, unchanging increase in muscle tone at rest regardless of movement speed
• B. Involuntary rhythmic oscillations of a joint during sustained stretch
• C. A velocity-dependent increase in muscle tone in response to passive stretch
• D. Flaccid paralysis below the level of the lesion with absent deep tendon reflexes

Answer: (C)

Spasticity after a spinal cord injury is the velocity-dependent increase in muscle tone that occurs with passive movement. When the limb is moved quickly, the stretch reflex is exaggerated because the brain’s normal inhibitory control over spinal reflex pathways is reduced. This makes the resistance rise as the movement speed increases, and you may also see features like hyperreflexia and, with sustained stretch, clonus. If you move slowly, the resistance is less pronounced. By contrast, a constant, non–speed-dependent increase in tone describes rigidity, not spasticity, and flaccid paralysis with absent reflexes points to a different state, often in the acute stage or involving lower motor neurons.

Spasticity after a spinal cord injury is the velocity-dependent increase in muscle tone that occurs with passive movement. When the limb is moved quickly, the stretch reflex is exaggerated because the brain’s normal inhibitory control over spinal reflex pathways is reduced. This makes the resistance rise as the movement speed increases, and you may also see features like hyperreflexia and, with sustained stretch, clonus. If you move slowly, the resistance is less pronounced. By contrast, a constant, non–speed-dependent increase in tone describes rigidity, not spasticity, and flaccid paralysis with absent reflexes points to a different state, often in the acute stage or involving lower motor neurons.