• Clinical science

Spasticity

Summary

Spasticity is defined as a velocity-dependent increase in muscle tone that manifests with resistance to movement and involuntary muscle spasms and contractions. It is caused by a lesion in the descending motor pathways. Common etiologies of spasticity include multiple sclerosis, stroke, tumor, cerebral palsy, and spinal or peripheral nerve injury. Nerve conduction studies and imaging of the brain and/or spinal cord may be requested to determine the underlying etiology. The management of spasticity is broad and may include physical and occupational therapy, pharmacotherapy (i.e., muscle relaxants such as diazepam, tizanidine, baclofen, or dantrolene; paralytics such as botulinum toxin), or surgery.

Etiology

An upper motor neuron lesion, commonly caused by:

References:[1]

Pathophysiology

  • The mechanism of spasticity is not completely understood.
  • It is thought that upper motor neuron damage leads to loss of descending inhibitory inputs → increased muscle stretch reflex → increased muscle tone

References:[1][2]

Clinical features

  • Increased muscle tone and velocity-dependent resistance to movement
    • Elicited by flexion and extension of various muscles with alternating speed
    • Clasp knife phenomenon: initial resistance (“catch”) when a limb is moved rapidly, followed by a sudden decrease in resistance; observed in patients with upper motor neuron lesions
    • Upper extremity flexors and lower extremity extensors are usually more affected.
    • Must be distinguished from rigidity
  • Involuntary muscle spasms or contractions

References:[3][1][2]

Diagnostics

  • Clinical diagnosis
  • Further tests (e.g., nerve conduction studies or brain imaging) depend on the suspected underlying etiology.

References:[1]

Treatment

References:[1]

Complications

  • Musculoskeletal deformity
  • Impaired mobility
  • Reduced functional independence
  • Pain

References:[1]

We list the most important complications. The selection is not exhaustive.

Prognosis

The prognosis of spasticity depends on the underlying condition.

References:[1]

  • 1. Vanek ZF, Berman SA. Spasticity. In: Spasticity. New York, NY: WebMD. http://emedicine.medscape.com/article/2207448-overview. Updated February 4, 2016. Accessed May 22, 2017.
  • 2. Ropper A, Klein J, Samuels M. Adams and Victor's Principles of Neurology 10th Edition. McGraw-Hill Education / Medical; 2014.
  • 3. Gelb D, Aminoff MJ, Wilterdink JL. The Detailed Neurologic Examination in Adults. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/the-detailed-neurologic-examination-in-adults. Last updated September 7, 2012. Accessed March 2, 2017.
  • Kobayashi H, Hasegawa Y, Ono H. Cyclobenzaprine, a centrally acting muscle relaxant, acts on descending serotonergic systems. Eur J Pharmacol. 1996; 311(1): pp. 29–35. doi: 10.1016/0014-2999(96)00402-5.
  • Brioschi TM de LS, Schramm SG, Kano EK, et al. Pharmacokinetics and Bioequivalence Evaluation of Cyclobenzaprine Tablets. BioMed Research International. 2013; 2013: pp. 1–6. doi: 10.1155/2013/281392.
last updated 03/19/2020
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