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2 - Neurophysiology of spasticity

Published online by Cambridge University Press:  22 August 2009

By
Geoff Sheean
Edited by
Michael P. Barnes  and
Garth R. Johnson
Geoff Sheean
Affiliation:
Professor Department of Neurosciences, University of California – San Diego Medical Centre San Diego, California, USA
Michael P. Barnes
Affiliation:
University of Newcastle upon Tyne
Garth R. Johnson
Affiliation:
University of Newcastle upon Tyne
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Summary

Introduction

The pathophysiology of spasticity is a complex subject and one frequently avoided by clinicians. Some of the difficulties relate to the definition of spasticity and popular misconceptions regarding the role of the pyramidal tracts. On a more basic level, the lack of a very good animal model has been a problem for physiologists. Nonetheless, a clear concept of the underlying neurophysiology will give the clinician better understanding of their patients' clinical features and provide a valuable basis upon which to make management decisions.

Definition

Some of the difficulty that clinicians experience with understanding the pathophysiology of spasticity is due to the definition of this condition. Most textbooks launch the discussion with a definition offered by Lance (1980) and generally accepted by physiologists:

Spasticity is a motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes (‘muscle tone’) with exaggerated tendon jerks, resulting from hyperexcitability of the stretch reflex, as one component of the upper motor neurone syndrome.

It may be difficult for clinicians to correlate this definition with a typical patient. They may see instead a patient with multiple sclerosis who has increased muscle tone in the legs, more in the extensors than the flexors, that appears to increase with the speed of the testing movements. They also recall a clasp-knife phenomenon at the knee, tendon hyperreflexia with crossed adductor reflexes, ankle clonus, extensor plantar responses, a tendency for flexor spasms and, on occasion, extensor spasms.

Keywords

contracturescutaneous reflexesneurophysiologynociceptive reflexesspasticityspinal reflexesupper motor neurone syndromeproprioceptive reflexes
Type
Chapter
Information
Upper Motor Neurone Syndrome and Spasticity
Clinical Management and Neurophysiology
 , pp. 9 - 63
Publisher: Cambridge University Press
Print publication year: 2008

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  • Neurophysiology of spasticity
    • By Geoff Sheean, Professor Department of Neurosciences, University of California – San Diego Medical Centre San Diego, California, USA
  • Edited by Michael P. Barnes, University of Newcastle upon Tyne, Garth R. Johnson, University of Newcastle upon Tyne
  • Book: Upper Motor Neurone Syndrome and Spasticity
  • Online publication: 22 August 2009
  • Chapter DOI: https://doi.org/10.1017/CBO9780511544866.003
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  • Neurophysiology of spasticity
    • By Geoff Sheean, Professor Department of Neurosciences, University of California – San Diego Medical Centre San Diego, California, USA
  • Edited by Michael P. Barnes, University of Newcastle upon Tyne, Garth R. Johnson, University of Newcastle upon Tyne
  • Book: Upper Motor Neurone Syndrome and Spasticity
  • Online publication: 22 August 2009
  • Chapter DOI: https://doi.org/10.1017/CBO9780511544866.003
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  • Neurophysiology of spasticity
    • By Geoff Sheean, Professor Department of Neurosciences, University of California – San Diego Medical Centre San Diego, California, USA
  • Edited by Michael P. Barnes, University of Newcastle upon Tyne, Garth R. Johnson, University of Newcastle upon Tyne
  • Book: Upper Motor Neurone Syndrome and Spasticity
  • Online publication: 22 August 2009
  • Chapter DOI: https://doi.org/10.1017/CBO9780511544866.003
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