title: Corticospinal excitability measurements using transcranial magnetic stimulation are valid with intramuscular electromyography.
abstract: OBJECTIVE
  Muscular targets that are deep or inaccessible to surface electromyography (sEMG) require intrinsic recording using fine-wire electromyography (fEMG). It is unknown if fEMG validly record cortically evoked muscle responses compared to sEMG. The purpose of this investigation was to establish the validity and agreement of fEMG compared to sEMG to quantify typical transcranial magnetic stimulation (TMS) measures pre and post repetitive TMS (rTMS). The hypotheses were that fEMG would demonstrate excellent validity and agreement compared with sEMG.
  
  
  METHODS
  In ten healthy volunteers, paired pulse and cortical silent period (CSP) TMS measures were collected before and after 1200 pulses of 1Hz rTMS to the motor cortex. Data were simultaneously recorded with sEMG and fEMG in the first dorsal interosseous. Concurrent validity (r and rho) and agreement (Tukey mean-difference) were calculated.
  
  
  RESULTS
  fEMG quantified corticospinal excitability with good to excellent validity compared to sEMG data at both pretest (r = 0.77-0.97) and posttest (r = 0.83-0.92). Pairwise comparisons indicated no difference between sEMG and fEMG for all outcomes; however, Tukey mean-difference plots display increased variance and questionable agreement for paired pulse outcomes. CSP displayed the highest estimates of validity and agreement. Paired pulse MEP responses recorded with fEMG displayed reduced validity, agreement and less sensitivity to changes in MEP amplitude compared to sEMG. Change scores following rTMS were not significantly different between sEMG and fEMG.
  
  
  CONCLUSIONS
  fEMG electrodes are a valid means to measure CSP and paired pulse MEP responses. CSP displays the highest validity estimates, while caution is warranted when assessing paired pulse responses with fEMG. Corticospinal excitability and neuromodulatory aftereffects from rTMS may be assessed using fEMG.
authors.affiliation: Program in Physical Therapy, Department of Physical Medicine and Rehabilitation, University of Minnesota, Minneapolis, MN, United States of America.|Department of Physical Medicine and Rehabilitation, Rehabilitation Science, University of Minnesota, Minneapolis, MN, United States of America.
authors.forename: Rebekah L S
authors.identifier: http://orcid.org/0000-0002-1783-3362
authors.initials: RL
authors.lastname: Summers
authors.affiliation: Department of Physical Medicine and Rehabilitation, Rehabilitation Science, University of Minnesota, Minneapolis, MN, United States of America.|Institute for Engineering in Medicine, University of Minnesota, Minneapolis, MN, United States of America.
authors.forename: Mo
authors.initials: M
authors.lastname: Chen
authors.affiliation: Program in Physical Therapy, Department of Physical Medicine and Rehabilitation, University of Minnesota, Minneapolis, MN, United States of America.|Department of Physical Medicine and Rehabilitation, Rehabilitation Science, University of Minnesota, Minneapolis, MN, United States of America.
authors.forename: Teresa J
authors.initials: TJ
authors.lastname: Kimberley
mesh_terms: D000328:Adult; D004576:Electromyography / Q000379:methods*; D019054:Evoked Potentials, Motor; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009119:Muscle Contraction; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D055815:Young Adult