Focally active medications are for specialist use in conjunction with physical treatments (e.g. splints).

1) Botulinum Neurotoxin (BoNTx) Injection:94022899-lh-dr-with-clipboard

  • Genetically engineered toxin derived from clostridium botulinum, a bacterium which causes botulism, a disease manifest by muscle paralysis.
  • It works by blocking presynaptic cholinergic nerve terminals.
  • Advantage in use is to target affected muscles, sometimes with the added benefit of augmenting effectiveness of antagonist muscles.
  • Treatment effect lasts 3 to 4 months, the time required for neural pathways to develop a new neuromuscular junction through new axonal sprouting.
  • Repeat injection at 3 to 4 monthly intervals are required.  Tolerance may develop over time and reduce effectiveness.
  • Treatment may be ineffective.  Reasons for this may include:
    • Inappropriate use in contracted rather than spastic muscle.
    • Poor muscle localisation.  Electromyography (EMG) or ultrasound guidance is strongly recommended to improve localisation.
    • Insufficient dose.
    • Development of tolerance.
  • Potential side effects include:
    • Paresis of injected muscle.
    • Paresis of adjacent muscles.
    • Local pain or haematoma.

2) Other Focal Treatment Options including:

a. Phenol injection/motor nerve block:430895416-phenol

  • Similar advantages to botulinum toxin in terms of local versus systemic effect.
  • But its use is limited for the following reasons:
    • Its use is only applicable in nerves that have predominantly motor (vs sensory) roles and in nerves which are easily accessible (typically tibial or obturator nerves or lumbar spinal cord).
    • It requires specialist expertise which is not widely available.

b. Intrathecal Baclofen Pump:

  • Useful when:
    • Spasticity is predominantly in lower limbs.
    • Complete loss of function in lower limbs is pre-existing and accepted.
    • All other treatment options have failed.
  • Principal risk arises from:
    • Administration errors or failures can lead to abrupt withdrawal or overdose syndromes.
    • Respiratory depression or central sedation if Baclofen disperses to cervico-thoracic regions.