title: Cortical Silent Period Reveals Differences Between Adductor Spasmodic Dysphonia and Muscle Tension Dysphonia.
abstract: BACKGROUND
  The pathophysiology of adductor spasmodic dysphonia (AdSD), like other focal dystonias, is largely unknown.
  
  
  OBJECTIVE
  The purposes of this study were to determine (a) cortical excitability differences between AdSD, muscle tension dysphonia (MTD), and healthy controls; (b) distribution of potential differences in cranial or skeletal muscle; and (c) if cortical excitability measures assist in the differential diagnosis of AdSD and MTD.
  
  
  METHODS
  Ten participants with adductor spasmodic dysphonia, 8 with muscle tension dysphonia, and 10 healthy controls received single and paired pulse transcranial magnetic stimulation (TMS) to the primary motor cortex contralateral to tested muscles, first dorsal interosseus (FDI), and masseter. We tested the hypothesis that cortical excitability measures in AdSD would be significantly different from those in MTD and healthy controls. In addition, we hypothesized that there would be a correlation between cortical excitability measures and clinical voice severity in AdSD.
  
  
  RESULTS
  Cortical silent period duration in masseter and FDI was significantly shorter in AdSD than MTD and healthy controls. Other measures failed to demonstrate differences.
  
  
  CONCLUSIONS
  There are differences in cortical excitability between AdSD, MTD, and healthy controls. These differences in the cortical measure of both the FDI and masseter muscles in AdSD suggest widespread dysfunction of the GABAB mechanism may be a pathophysiologic feature of AdSD, similar to other forms of focal dystonia. Further exploration of the use of TMS to assist in the differential diagnosis of AdSD and MTD is warranted.
authors.affiliation: University of Minnesota, Minneapolis, MN, USA University of Wisconsin, River Falls, WI, USA sharyl.samargia@uwrf.edu.
authors.forename: Sharyl
authors.initials: S
authors.lastname: Samargia
authors.affiliation: University of Minnesota, Minneapolis, MN, USA.
authors.forename: Rebekah
authors.initials: R
authors.lastname: Schmidt
authors.affiliation: University of Minnesota, Minneapolis, MN, USA.
authors.forename: Teresa Jacobson
authors.initials: TJ
authors.lastname: Kimberley
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D055154:Dysphonia / Q000175:diagnosis / Q000503:physiopathology* / Q000628:therapy; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008406:Masseter Muscle / Q000503:physiopathology; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D009129:Muscle Tonus / Q000502:physiology; D018482:Muscle, Skeletal / Q000503:physiopathology; D012720:Severity of Illness Index; D050781:Transcranial Magnetic Stimulation / Q000009:adverse effects / Q000379:methods; D016896:Treatment Outcome; D014833:Voice Quality / Q000502:physiology; D055815:Young Adult
keywords: adductor spasmodic dysphonia; cortical silent period; muscle tension dysphonia; transcranial magnetic stimulation