Botulinum toxin type-A treatment in spastic paraparesis: a neurophysiological study

J Neurol Sci. 2000 Dec 1;181(1-2):89-97. doi: 10.1016/s0022-510x(00)00439-1.


Objective: The aim of this study was to verify the action of Botulinum toxin type-A (BoNT-A) by means of neurophysiological techniques, in patients presenting lower limb spasticity and requiring BoNT-A injections in the calf muscles, due to the poor response to medical antispastic treatment.

Subjects and method: Patients presenting paraparesis were enrolled. They underwent clinical evaluation for spasticity according to the Ashworth scale and neurophysiological recordings including: motor evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) of the leg area; compound motor action potential (cMAP) to tibial nerve stimulation, F-wave, and H-reflex before the treatment and 24 h, 2 weeks and 1 month after the injection of BoNT-A. In all patients, gastrocnemius was treated and in some cases soleus or tibialis posterior muscles were also injected.

Results: In all patients, BoNT-A injections induced a clear clinical improvement as showed by the reduced spasticity values of the Ashworth scale. A significant increment of MEP latency and central conduction time (CCT) duration were observed 2 weeks after the treatment only in the injected muscles.

Conclusions: Prolonged MEP latencies and CCT after BoNT-A injections is probably due to a central alteration in responsiveness of spinal motor neurons to descending impulses from the corticospinal tracts. Such changes represent objective parameters heralding clinical efficacy of treatment.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Botulinum Toxins, Type A / administration & dosage*
  • Botulinum Toxins, Type A / adverse effects
  • Electric Stimulation
  • Evoked Potentials, Motor / drug effects
  • Evoked Potentials, Motor / physiology
  • Female
  • Functional Laterality / drug effects
  • Functional Laterality / physiology
  • H-Reflex / drug effects
  • H-Reflex / physiology
  • Humans
  • Magnetics
  • Male
  • Middle Aged
  • Motor Neurons / drug effects
  • Motor Neurons / physiology
  • Muscle, Skeletal / drug effects
  • Muscle, Skeletal / physiopathology
  • Neural Conduction / drug effects
  • Neural Conduction / physiology
  • Paraparesis, Spastic / drug therapy*
  • Paraparesis, Spastic / physiopathology
  • Peripheral Nerves / drug effects
  • Peripheral Nerves / physiopathology
  • Pyramidal Tracts / drug effects
  • Pyramidal Tracts / physiopathology
  • Reaction Time / drug effects
  • Reaction Time / physiology
  • Spinal Cord / drug effects
  • Spinal Cord / physiopathology


  • Botulinum Toxins, Type A