Physiological effects produced by botulinum toxin treatment of upper limb dystonia: Changes in reciprocal inhibition between forearm muscles

Alberto Priori, Alfredo Berardelli, Bruno Mercuri, Mario Manfredi

Research output: Contribution to journalArticlepeer-review

Abstract

Patients with upper limb dystonia have abnormal reciprocal inhibition between flexor and extensor forearm muscles. To see whether botulinum toxin treatment alters segmental motor system function, we studied reciprocal inhibition between forearm flexor and extensor muscles, before and after botulinum toxin injection In forearm muscles in 12 patients with upper limb dystonia. Reciprocal inhibition was studied by conditioning the H reflex in forearm flexors with a radial nerve stimulus delivered at a range of time intervals. Botulinum toxin injection improved upper limb dystonia. Before botulinum toxin injection, the dystonic patients had a decreased second phase of reciprocal inhibition. After botulinum toxin injections this second abnormal phase of reciprocal inhibition increased. Botulinum toxin did not change the first phase of reciprocal inhibition. Botulinum toxin treatment also reduced the M wave and the H reflex by a similar amount but left the Hmax:Mmax ratio unchanged. Ample evidence has shown that the therapeutic effects of botulinum toxin in dystonia depend mainly on its neuromuscular junction blocking action. Our data now suggest a concurrent indirect effect on spinal cord circuitry, probably through the action of botulinum toxin on the intrafusal neuromuscular junction.

Original languageEnglish
Pages (from-to)801-807
Number of pages7
JournalBrain
Volume118
Issue number3
Publication statusPublished - Jun 1995

Keywords

  • Botulinum toxin
  • H reflex
  • Reciprocal inhibition
  • Upper limb dystonia

ASJC Scopus subject areas

  • Neuroscience(all)
  • Statistics, Probability and Uncertainty
  • Applied Mathematics
  • Mathematics(all)
  • Statistics and Probability
  • Agricultural and Biological Sciences (miscellaneous)
  • Clinical Neurology

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