Review of electrical stimulation, botulinum toxin, and their combination for spastic drop foot

1
Review of electrical stimulation, botulinum
toxin, and their combination for spastic drop
foot

• Ari Jacob Levi Wilkenfeld, MD, PhD

2

• Aim
• Review pathophysiology of spastic drop foot and
  its treatment options.
• Present theoretical reasons why functional
  electrical stimulation (ES) and botulinum toxin
  (BTX) injections could work synergistically.
• Relevance
• There are reasons to think functional ES and BTX
  injections might work effectively in combination,
  but no clear consensus exists in literature.

3
Background

• Spastic drop foot
• Weak ankle dorsiflexors and spastic ankle plantar
  flexors predispose ankle to stay pathologically
  plantar flexed.
• Functional ES
• Uses electric current to activate muscles and
  nerves that are weak/paralyzed but still have
  intact lower motor neurons and musculature.
• BTX
• Prevents acetylcholine release at presynaptic
  terminal, thus impairing neuromuscular
  transmission and inducing weakness.

4
Treatment

• 4 mechanisms by which ES might increase
  antispasticity effect of BTX.
• Animal experiments BTXs paralytic effect starts
  earlier when toxin uptake is increased with ES.
• Moving muscle through flexion/extension cycles
  could help mechanically spread toxin.
• Direct effects of ES on tone reduction.
• Simultaneously addressing positive and negative
  components of upper motor neuron syndrome could
  lead to increased functional gains in gait.

5
Conclusions

• For ES Evidence of decreased spasticity.
• But, e.g., whether stimulation should be over
  spastic muscle or its antagonist, how long effect
  lasts, and whether it works during gait must be
  clarified.
• For BTX Evidence of decreased tone.
• But evidence lacking for improved gait.
• ESBTX Evidence that ES of muscle may increase
  efficacy of BTX.
• However, large controlled studies examining
  relative effects are lacking.