What is the pathophysiology of spasticity?

Updated: Jun 28, 2019
  • Author: Krupa Pandey, MD; Chief Editor: Stephen A Berman, MD, PhD, MBA  more...
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The pathophysiologic basis of spasticity is incompletely understood. Polysynaptic responses may be involved in spinal cord–mediated spasticity, while enhanced excitability of monosynaptic pathways is involved in cortically mediated spasticity.

Spasticity-related changes in muscle tone probably result from alterations in the balance of inputs from reticulospinal and other descending pathways to the motor and interneuronal circuits of the spinal cord, along with the absence of an intact corticospinal system. Loss of descending tonic or phasic excitatory and inhibitory inputs to the spinal motor apparatus, alterations in the segmental balance of excitatory and inhibitory control, denervation supersensitivity, and neuronal sprouting may be observed.

Once spasticity is established, the chronically shortened muscle may develop physical changes, such as shortening and contracture, that further contribute to muscle stiffness. [7]

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