Botulinum toxin changes intrafusal feedback in dystonia: a study with the tonic vibration reflex

Mov Disord. 2006 Jun;21(6):777-82. doi: 10.1002/mds.20801.


To investigate the possible role of botulinum toxin (BT-A) injection in reducing muscle afferent feedback, we evaluated electrophysiologically 10 right-handed patients with writer's cramp before and 3 weeks after treatment. The ratio between pre- and postinjection values of maximal M-wave (M-max), maximal voluntary contraction (MVC), and tonic vibration reflex (TVR) were measured in the injected muscles (wrist flexors or extensors). In all the subjects, BT-A injection reduced the TVR more than the M-max and MVC (mean ratio +/- SD: TVR, 0.24 +/- 0.22; MVC, 0.59 +/- 0.32; M-max, 0.68 +/- 0.24; P = 0.003). Long-term evaluation of 2 patients disclosed that, after 7 months, when some clinical benefits persisted, M-max and MVC had fully recovered, whereas the TVR was still depressed. This special sensitivity of the TVR to suppression by BT-A injection could be mediated by the chemodenervation of intrafusal muscle fibers, leading to a reduction in spindle inflow to the central nervous system during vibration. The action on intrafusal fibers could alter sensorimotor integration, thus contributing to the clinical benefits of BT-A injection.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Afferent Pathways / drug effects
  • Afferent Pathways / physiopathology
  • Aged
  • Botulinum Toxins / pharmacology*
  • Dystonia / physiopathology*
  • Feedback / drug effects*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Motor Activity / drug effects*
  • Muscle Contraction / drug effects*
  • Reflex
  • Vibration


  • Botulinum Toxins