Evidence for normal intracortical inhibitory recruitment properties in cervical dystonia

Rebekah L S Summers; Mo Chen; Colum D MacKinnon; Teresa J Kimberley

doi:10.1016/j.clinph.2020.03.019

Evidence for normal intracortical inhibitory recruitment properties in cervical dystonia

Clin Neurophysiol. 2020 Jun;131(6):1272-1279. doi: 10.1016/j.clinph.2020.03.019. Epub 2020 Apr 2.

Authors

Rebekah L S Summers¹, Mo Chen², Colum D MacKinnon³, Teresa J Kimberley⁴

Affiliations

¹ Divisions of Physical Therapy and Rehabilitation Science, Department of Rehabilitation Medicine, School of Medicine, University of Minnesota, 426 Church St. SE, Minneapolis, MN 55455, USA; Department of Neurology, School of Medicine, University of Minnesota, 717 Delaware St. SE, Minneapolis, MN 55414, USA. Electronic address: Schm2203@umn.edu.
² Divisions of Physical Therapy and Rehabilitation Science, Department of Rehabilitation Medicine, School of Medicine, University of Minnesota, 426 Church St. SE, Minneapolis, MN 55455, USA; Non-invasive Neuromodulation Laboratory, MnDRIVE Initiative, University of Minnesota, 247, 717 Delaware St. SE, Minneapolis, MN 55414, USA.
³ Department of Neurology, School of Medicine, University of Minnesota, 717 Delaware St. SE, Minneapolis, MN 55414, USA.
⁴ Divisions of Physical Therapy and Rehabilitation Science, Department of Rehabilitation Medicine, School of Medicine, University of Minnesota, 426 Church St. SE, Minneapolis, MN 55455, USA; School of Health and Rehabilitation Sciences, Department of Physical Therapy, Massachusetts General Hospital, Institute of Health Professions, 36 First Ave, Boston, MA 02129, USA.

Abstract

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 normal intracortical inhibition recruitment properties challenge the commonly held view that cortical inhibition is reduced in dystonia.

Keywords: Cortical excitability; Cortical silent period; Dystonia; Motor evoked potential; Transcallosal inhibition; Transcranial magnetic stimulation.

Publication types

Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

MeSH terms

Adult
Cerebral Cortex / physiopathology*
Electroencephalography
Electromyography
Evoked Potentials, Motor / physiology*
Female
Humans
Male
Middle Aged
Motor Cortex / physiopathology*
Neural Inhibition / physiology*
Superficial Back Muscles / physiopathology*
Torticollis / physiopathology*
Transcranial Magnetic Stimulation

Abstract

Publication types

MeSH terms

Grants and funding