Objective: Dystonia is associated with reduced intracortical inhibition as measured by the cortical silent period (cSP); however, this may be due to abnormal cSP threshold or input-output properties. This study evaluated cSP recruitment properties in people with cervical dystonia (CD). Methods: Bilateral electromyographic recordings were collected in the upper trapezius muscle in response to transcranial magnetic stimulation of the left and right primary motor cortex in a group with CD (n = 19) and controls (n = 21). cSP threshold, cSP input-output properties at stimulation intensities from 1 to 1.4x the cSP threshold, ipsilateral silent period duration (iSP) and timing and magnitude of the contralateral and ipsilateral motor evoked potential (MEP) were assessed. Results: The cSP threshold, input-output properties, and contralateral MEP magnitude were not significantly different between groups (all p > 0.07). Hemispheric symmetry was present in the control group while the CD group had reduced iSP (p < 0.01) and a trend for reduced ipsilateral MEP response (p = 0.053) in the left hemisphere. Conclusions: Recruitment properties of intracortical inhibition are similar between control and CD groups. Transcallosal inhibition is asymmetric between hemispheres in people with CD. Significance: Evidence of normative intracortical inhibition recruitment properties challenge the commonly held view that cortical inhibition is reduced in dystonia.
Bibliographical noteFunding Information:
We thank the following staff for their assistance collecting data: Alana Lieske, Michael Plant, Jared Hoffmann, Aaron Miller, Matthew Gehrke, and Aaron Moyer. This work was supported by the National Institutes of Health’s National Center for Advancing Translational Sciences (grants TL1R002493 , UL1TR000114 , and UL1TR002494 ), University of Minnesota Doctoral Dissertation Fellowship , University of Minnesota’s MnDRIVE (Minnesota’s Discovery, Research and Innovation Economy) initiative, Foundation for Physical Therapy (Promotion of Doctoral Studies II award), and the Divisions of Rehabilitation Science and Physical Therapy , Department of Rehabilitation Medicine, University of Minnesota .
© 2020 International Federation of Clinical Neurophysiology
- Cortical excitability
- Cortical silent period
- Motor evoked potential
- Transcallosal inhibition
- Transcranial magnetic stimulation
PubMed: MeSH publication types
- Journal Article
- Research Support, N.I.H., Extramural
- Research Support, Non-U.S. Gov't