Spasticity

Bailey Frei

Background 

  • Spasticity is a velocity-dependent increase in resistance to passive stretch.
  • It differs from hypertonia, which is resistance to passive stretch that is not velocity-dependent
  • Spasticity is believed to result from disruption of descending inhibitory modulation of the alpha motor neurons by an upper motor lesion, producing hyperexcitability
  • Grading (by the Modified Ashworth Scale)
    • 0: no increase in tone
    • 1: slight increase in muscle tone, manifested by a catch and release or by minimal resistance at the end of ROM when affected part is moved in flexion or extension
    • 1+: slight increase in muscle tone, manifested by a catch followed by minimal resistance through the remainder of ROM (less than 50%)
    • 2: more marked increase in muscle tone through most of ROM, but affected part is easily moved
    • 3: considerable increases in muscle tone; passive movement difficult
    • 4: affected part is rigid in flexion or extension

Management 

  • Spasticity can have functional benefits, including improving standing and transfers. However, it can also cause weakness, poor dexterity, pain, and contractures.
  • If spasticity is having undesirable effects, the first line of treatment is PT/OT and physical modalities such as stretching.
  • Oral medications are the next line of treatment.

Medication

Mechanism of Action

Side Effects/Important Considerations
Baclofen GABA-B agonist sedation, fatigue, nausea, centrally acting – risk of withdrawal
Tizanidine Alpha-2 agonist sedation, dizziness, xerostomia, weakness, centrally acting – risk of withdrawal
Diazepam/ Benzodiazepines GABA-A agonist sedation, confusion, hypotension, centrally acting – risk of withdrawal
Dantrolene inhibits Ca release from sarcoplasmic reticulum weakness, sedation, nausea, hepatotoxicity, acts directly on skeletal muscle
  • Intrathecal baclofen: reserved for pts who have significant side effects with oral anti-spasticity medications or who have severe, persistent, and diffuse spasticity despite maximal doses
  • Injections
    • Botulinum toxin: Blocks the presynaptic release of acetylcholine from motor endplates of the lower motor neuron at the myoneural junction. Effect usually lasts 3-8months
    • Alcohol block: Phenol and ethanol are neurolytic agents that can be used to block nerves with motor function.
  • Surgeries
    • Selective dorsal rhizotomy, osteotomy, muscle tendon lengthening, release, or transfer

***If a pt experiences worsening of spasticity, it is important to consider other underlying conditions such as infections, pressure ulcers, constipation, or bladder distention***

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