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Spasticity

Doug Bryant and Jake Dovgan

Background

  • Spasticity is a velocity-dependent increase in resistance to passive stretch.

  • It differs from hypertonia in that hypertonia 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 half)

  • 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, first line of treatment is PT/OT and physical modalities such as stretching.

  • Oral Medications

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