Session Information
Date: Thursday, June 23, 2016
Session Title: Dystonia
Session Time: 12:00pm-1:30pm
Location: Exhibit Hall located in Hall B, Level 2
Objective: To investigate the effects of rapid paired associative stimulation (PAS) in organic and psychogenic dystonia to see if this technique can differentiate them.
Background: PAS is an established measure of cortical plasticity that is obtained by pairing transcranial magnetic stimulation and peripheral nerve stimulation set to arrive at the same time to the motor cortex. Dystonia is a disease of abnormal muscle contractions, associated with abnormal cortical plasticity as measured by PAS. One study has previously shown promise in using the technique to differentiate organic from psychogenic dystonia, but this has not been reproduced. Rapid PAS decreases testing time, minimizing subject and investigator fatigue.
Methods: We designed an internal pilot study of 18 participants, then repowering using the primary outcome measure of change from baseline of motor evoked potential amplitudes at 30 minutes after rapid PAS. Six patients with organic dystonia, six patients with psychogenic dystonia and six healthy volunteers underwent transcranial magnetic stimulation using 5 Hz rapid PAS protocol. Motor evoked potentials were recorded at S50 intensity and over a range of stimulus intensities and a sigmoidal recruitment curve was fitted at four time points (baseline, immediately after, 30 minutes after, and one hour after rapid PAS). All subjects also had temporal discrimination thresholds (TDT) and short interval intracortical inhibition (SICI) measured.
Results: No significant group differences were found in the TDT, SICI, motor recruitment curve parameters or motor evoked potential amplitudes change from baseline at all time points in the study. Repowering produced an impractical number needed to proceed with the study, and the study was halted. One patient with organic dystonia had to be withdrawn from the study because no reliable motor evoked potential amplitudes could be obtained.
Conclusions: The present study shows that rapid PAS, TDT, and SICI do not easily differentiate between organic and psychogenic dystonia.
Submitted to the American Academy of Neurology meeting April 2016.
To cite this abstract in AMA style:
V.F.M. Ramos, P. Srivanitchapoom, S. Pandey, A. Holmes, S. Kukke, R. Paine, N. Thirugnanasanbandam, N. Dang, M. Hallett. Investigating the plastic effects of rapid paired associative stimulation in dystonia [abstract]. Mov Disord. 2016; 31 (suppl 2). https://www.mdsabstracts.org/abstract/investigating-the-plastic-effects-of-rapid-paired-associative-stimulation-in-dystonia/. Accessed June 14, 2025.« Back to 2016 International Congress
MDS Abstracts - https://www.mdsabstracts.org/abstract/investigating-the-plastic-effects-of-rapid-paired-associative-stimulation-in-dystonia/