title: Reliability of TMS metrics in patients with chronic incomplete spinal cord injury.
abstract: METHODS
  Test-retest reliability analysis in individuals with chronic incomplete spinal cord injury (iSCI).
  
  
  OBJECTIVE
  The purpose of this study was to examine the reliability of neurophysiological metrics acquired with transcranial magnetic stimulation (TMS) in individuals with chronic incomplete tetraplegia.
  
  
  METHODS
  Cleveland Clinic Foundation, Cleveland, Ohio, USA.
  
  
  METHODS
  TMS metrics of corticospinal excitability, output, inhibition and motor map distribution were collected in muscles with a higher MRC grade and muscles with a lower MRC grade on the more affected side of the body. Metrics denoting upper limb function were also collected. All metrics were collected at two sessions separated by a minimum of two weeks. Reliability between sessions was determined using Spearman's correlation coefficients and concordance correlation coefficients (CCCs).
  
  
  RESULTS
  We found that TMS metrics that were acquired in higher MRC grade muscles were approximately two times more reliable than those collected in lower MRC grade muscles. TMS metrics of motor map output, however, demonstrated poor reliability regardless of muscle choice (P=0.34; CCC=0.51). Correlation analysis indicated that patients with more baseline impairment and/or those in a more chronic phase of iSCI demonstrated greater variability of metrics.
  
  
  CONCLUSIONS
  In iSCI, reliability of TMS metrics varies depending on the muscle grade of the tested muscle. Variability is also influenced by factors such as baseline motor function and time post SCI. Future studies that use TMS metrics in longitudinal study designs to understand functional recovery should be cautious as choice of muscle and clinical characteristics can influence reliability.
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH, USA.
authors.forename: K A
authors.initials: KA
authors.lastname: Potter-Baker
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH, USA.
authors.forename: D P
authors.initials: DP
authors.lastname: Janini
authors.affiliation: Department of Physical Medicine and Rehabilitation, Neurological Institute, Cleveland Clinic Foundation, Cleveland OH, USA.
authors.forename: F S
authors.initials: FS
authors.lastname: Frost
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH, USA.
authors.forename: P
authors.initials: P
authors.lastname: Chabra
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH, USA.
authors.forename: N
authors.initials: N
authors.lastname: Varnerin
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH, USA.|School of Biomedical Sciences, Kent State University, Kent, OH, USA.
authors.forename: D A
authors.initials: DA
authors.lastname: Cunningham
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH, USA.
authors.forename: V
authors.initials: V
authors.lastname: Sankarasubramanian
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH, USA.|Department of Physical Medicine and Rehabilitation, Neurological Institute, Cleveland Clinic Foundation, Cleveland OH, USA.|Center for Neurological Restoration, Neurosurgery, Neurological Institute, Cleveland Clinic Foundation, Cleveland Clinic, Cleveland, OH, USA.
authors.forename: E B
authors.initials: EB
authors.lastname: Plow
mesh_terms: D000368:Aged; D001931:Brain Mapping; D002908:Chronic Disease; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology; D011712:Pyramidal Tracts / Q000503:physiopathology; D011930:Reaction Time / Q000502:physiology; D015203:Reproducibility of Results; D013119:Spinal Cord Injuries / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation