What is Spasticity? Currently Accepted Definition for Occupational Therapy Practice vs Older Definitions

A common complication after a stroke is spasticity. Spasticity has been defined differently over the years.

One of the most popular definitions for spasticity reads something like this:

‘a motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes with exaggerated tendon jerks, resulting from hyperexcitability of the stretch reflex, as one component of the upper motor neuron syndrome'((Lance JW. Symposium synopsis. In: , Feldman RG, Young R, Koella WP, eds. Spasticity:disordered Motor ControlChicago, ILYear Book Medical Publishers1980:485–494))

Some early definitions of spasticity proposed from the 1980s-1990s include:

‘An increase in muscle tone varying from a mild degree to a state approximating to decerebrate rigidity, depending upon the seat of the lesion and the extent of co-involvement of the extrapyramidal system’

‘An exaggeration of proprioceptive reflex function due to the absence of some normal factor which conditions such function’

A more recent 2007 and simple definition of spasticity is a ‘velocity-dependent increase in stretch reflexes’.((Ibuki, A., & Bernhardt, J. (2007). What is spasticity? The discussion continues. International Journal of Therapy and Rehabilitation14(9), 391-395.))

It is also important to distinguish and differentiate spasticity from other similar, but different terms. These terms won’t be defined here as it is beyond the scope of this article.

  • Hyperreflexia
  • Hypertonia
  • Rigidity
  • Range of movement
  • Contracture
  • Associated movement
  • Spasm
  • Clonus

Historically, Lance’s (1980) definition which included ‘velocity-dependent’ was useful as it helped to distinguish spasticity from the terms mentioned. One downside to Lance’s definition is that it does not include aspects of sensory input into the experience.((Kuo, C. L., & Hu, G. C. (2018). Post-stroke spasticity: a review of epidemiology, pathophysiology, and treatments. International Journal of Gerontology12(4), 280-284.))

The most current definition(s) of spasticity seem to have omitted this part. Many definitions have been and continue to be proposed. The simpler of these ones proposed from the 2000s include:

‘Disordered sensory motor control resulting from an upper motor neurone lesion, presenting as intermittent or sustained involuntary activation of muscles’ [SPASM: Support Program for Assembly of a Database for Spasticity Management]

‘…stiffness of muscles that occurs when injury to the spinal cord or brain prevents nerve signals from reaching areas of the spinal cord …’

‘changes in movement associated with alterations in the CNS due to developmental abnormality, trauma or disease’

So are these more modern definitions better than the originally proposed ones?

To me, they seem more general and broader descriptions of the phenomenon. However, the upside is that they take into account the elastic properties of the soft tissue and sensory pathways.

So the question can still kind of remain: what is spasticity?

Despite this, experts recommend that when using the term spasticity, it is important to define precisely or describe what particular aspect you are treating.((Wood DE, Burridge JH, Van Wijck FM et al (2005) Biomechanical approaches applied to the lower and upper limb for the measurement of spasticity: A systematic review of the literature. Disabil Rehabil 27: 19–32))