Stretch reflex responses in Complex Regional Pain Syndrome-related dystonia are not characterized by hyperreflexia

W. Mugge, Alfred Christiaan Schouten, G.J. Bast, J. Schuurmans, J.J. van Hilten, F.C.T. van der Helm

Research output: Contribution to journalArticleAcademicpeer-review

6 Citations (Scopus)

Abstract

Objective To evaluate if hyperreflexia (exaggerated reflexes) due to disinhibition is associated with dystonia in Complex Regional Pain Syndrome (CRPS). Methods Stretch reflexes at the wrist were assessed in healthy controls (n = 10) and CRPS-patients with dystonia (n = 10). Subjects exerted a wrist flexion torque of 5% of maximum voluntary contraction torque (TMVC) to a manipulandum which applied ramp-and-hold stretches to the wrist flexors. Since reflex responses scale with background contraction, controls additionally performed the task at 1% and 3% TMVC to attain similar torques as patients who have reduced TMVC. The M1 onset and the magnitudes of the short latency M1 and long latency M2 were assessed using the electromyographic signals (EMG) of the flexor carpi radialis. EMG of the extensor carpi radialis was recorded to monitor cocontraction. Results Compared to controls, patients had a substantially reduced TMVC. Ramp velocity had a significant effect on M1 onset time and magnitude. Conclusions Since M1 magnitude decreased with flexion torque, no significant difference was found between patients and controls at 5% TMVC, while comparison at similar absolute torques (controls at 1% TMVC) resulted in significantly smaller M1 magnitudes for patients with dystonia.
Original languageEnglish
Pages (from-to)569-576
Number of pages8
JournalClinical neurophysiology
Volume123
Issue number3
DOIs
Publication statusPublished - 2012

Keywords

  • METIS-292633
  • IR-84965

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