BACKGROUND: Reduced intracortical inhibition is a neurophysiologic finding in focal dystonia that suggests a broader problem of impaired cortical excitability within the brain. A robust understanding of the neurophysiology in dystonia is essential to elucidate the pathophysiology of the disorder and develop new treatments. The cortical silent period (cSP) is a reliable, non-invasive method to measure intracortical inhibition in the primary motor cortex associated with a muscle of interest. In adductor spasmodic dysphonia (AdSD), cSP of the laryngeal motor cortex (LMC) which directly corresponds to the affected musculature, the thyroarytenoid (TA), has not been examined.
OBJECTIVE: This work evaluated the cSP of the LMC and the relationship between cSP and functional magnetic resonance imaging (fMRI) blood-oxygen-level dependent (BOLD) activation in people with AdSD (n = 12) compared to healthy controls (CTL, n = 14).
RESULTS: Shortened LMC cSP were observed bilaterally in people with AdSD vs CTL (F (1, 99) = 19.5226, p < 0.0001), with a large effect size (η 2 = 0.1834). Between-group fMRI analysis revealed greater activation in bilateral LMC in the AdSD > CTL contrast as compared to CTL > AdSD contrast. Correlation analysis showed that people with AdSD have positive correlation of left LMC BOLD activation and the cSP. Further, the right LMC cSP lacks either positive or negative associations with BOLD activation. CTL individuals displayed both positive and negative correlations between cSP and BOLD activation in the left LMC. In CTL, the LMC cSP and BOLD activation showed exclusively negative correlations in both hemispheres.
CONCLUSION: In AdSD, the cortical activation during phonation may not be efficiently or effectively associated with inhibitory processes, leading to muscular dysfunction. These findings may give insight into the maladaptive cortical control during phonation in people with AdSD.
Bibliographical noteFunding Information:
This work was partly supported by the National Institute of Communication Disorders and Deafness , National Institutes of Health ( R21DC012344 , 1R01DC015216 ); Research Grants, National Spasmodic Dysphonia Association (NSDA) .
We acknowledge the support provided by the University of Minnesota’s MnDRIVE (Minnesota’s Discovery, Research and Innovation Economy) initiative, Brain Conditions Program in this work. We thank Yi Ling Kuo for editorial assistance.
© 2020 The Author(s)
- Adductor spasmodic dysphonia
- Cortical silent period
- Laryngeal motor cortex
- Thyroarytenoid, laryngeal dystonia
- Transcranial magnetic stimulation
- Middle Aged
- Magnetic Resonance Imaging/methods
- Motor Cortex/diagnostic imaging
- Transcranial Magnetic Stimulation/methods
- Dysphonia/diagnostic imaging
PubMed: MeSH publication types
- Research Support, Non-U.S. Gov't
- Journal Article
- Research Support, N.I.H., Extramural