title: Plastic changes in spinal synaptic transmission following botulinum toxin A in patients with post-stroke spasticity.
abstract: OBJECTIVE
  The therapeutic effects of intramuscular injections of botulinum toxin-type A on spasticity can largely be explained by its blocking action at the neuromuscular junction. Botulinum toxin-type A is also thought to have a central action on the functional organization of the central nervous system. This study assessed the action of botulinum toxin-type A on spinal motor networks by investigating post-activation depression of the soleus H-reflex in post-stroke patients. Post-activation depression, a presynaptic mechanism controlling the synaptic efficacy of Ia-motoneuron transmission, is involved in the pathophysiology of spasticity.
  
  
  METHODS
  Eight patients with chronic hemiplegia post-stroke presenting with lower limb spasticity and requiring botulinum toxin-type A injection in the ankle extensor muscle.
  
  
  METHODS
  Post-activation depression of soleus H-reflex assessed as frequency-related depression of H-reflex was investigated before and 3, 6 and 12 weeks after botulinum toxin-type A injections in the triceps surae. Post-activation depression was quantified as the ratio between H-reflex amplitude at 0.5 and 0.1 Hz.
  
  
  RESULTS
  Post-activation depression of soleus H-reflex, which is reduced on the paretic leg, was affected 3 weeks after botulinum toxin-type A injection. Depending on the residual motor capacity of the post-stroke patients, post-activation depression was either restored in patients with preserved voluntary motor control or further reduced in patients with no residual voluntary control.
  
  
  CONCLUSIONS
  Botulinum toxin treatment induces synaptic plasticity at the Ia-motoneuron synapse in post-stroke paretic patients, which suggests that the effectiveness of botulinum toxin-type A in post-stroke rehabilitation might be partly due to its central effects.
authors.affiliation: APHM, Hôpital de la Timone, Pôle de Médecine Physique et de Réadaptation, FR-13385, Marseille, France. E-mail : marjorie.kerzoncuf@ap-hm.fr.
authors.forename: Marjorie
authors.initials: M
authors.lastname: Kerzoncuf
authors.forename: Laurent
authors.initials: L
authors.lastname: Bensoussan
authors.forename: Alain
authors.initials: A
authors.lastname: Delarque
authors.forename: Jacques
authors.initials: J
authors.lastname: Durand
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Viton
authors.forename: Christiane
authors.initials: C
authors.lastname: Rossi-Durand
mesh_terms: D019274:Botulinum Toxins, Type A / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007273:Injections, Intramuscular; D008297:Male; D008875:Middle Aged; D009128:Muscle Spasticity / Q000188:drug therapy*; D009465:Neuromuscular Agents / Q000627:therapeutic use*; D013131:Spine / Q000187:drug effects* / Q000473:pathology; D000071939:Stroke Rehabilitation; D009435:Synaptic Transmission / Q000187:drug effects*
chemical_list: D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A