title: Intracortical inhibition abnormality during the remission phase of multiple sclerosis is related to upper limb dexterity and lesions.
abstract: OBJECTIVE
  The impact of inhibitory cortical activity on motor impairment of people with relapsing-remitting multiple sclerosis (RRMS) has not been fully elucidated despite its relevance to neurorehabilitation. The present study assessed the extent to which transcranial magnetic stimulation (TMS)-based metrics of intracortical inhibition are related to motor disability and brain damage.
  
  
  METHODS
  Participants included forty-three persons with RRMS in the remitting phase and twenty-nine healthy controls. We stimulated the dominant hemisphere and recorded from the dominant hand to assess short-interval intracortical inhibition (SICI) and cortical silent period (CSP) duration. Disability was evaluated with the Multiple Sclerosis Functional Composite (MSFC). Regional cortical thickness and lesion volume were measured.
  
  
  RESULTS
  RRMS participants with dominant upper limb dexterity impairments had prolonged CSP, but equivalent SICI, compared to participants with preserved function. CSP was not related to walking or cognitive performance. Higher normalized lesion volume correlated with longer CSP duration. When adjusting for normalized lesion volume, longer CSP significantly predicted worse dominant upper extremity impairment.
  
  
  CONCLUSIONS
  High intracortical inhibition possibly contributes to (or prevents remission from) motor impairment. Lesions may be associated with intracortical inhibition shifts.
  
  
  CONCLUSIONS
  CSP duration and lesion burden should be considered when developing interventions aiming to mitigate motor impairment.
authors.affiliation: Integrated Program in Neuroscience, McGill University, 3801 University Street, Room 141, Montreal, Que. H3A 2B4, Canada; Research Institute of the McGill University Health Centre, 2155 Guy Street, 5th Floor, Montreal, Que. H3H 2R9, Canada. Electronic address: julia.nantes@mail.mcgill.ca.
authors.forename: Julia C
authors.initials: JC
authors.lastname: Nantes
authors.affiliation: Research Institute of the McGill University Health Centre, 2155 Guy Street, 5th Floor, Montreal, Que. H3H 2R9, Canada; Department of Neurology and Neurosurgery, McGill University, 845 Rue Sherbrooke Ouest, Montréal, Que., Canada. Electronic address: jidan.zhong@mail.mcgill.ca.
authors.forename: Jidan
authors.initials: J
authors.lastname: Zhong
authors.affiliation: Integrated Program in Neuroscience, McGill University, 3801 University Street, Room 141, Montreal, Que. H3A 2B4, Canada; Research Institute of the McGill University Health Centre, 2155 Guy Street, 5th Floor, Montreal, Que. H3H 2R9, Canada. Electronic address: scott.holmes@mail.mcgill.ca.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Holmes
authors.affiliation: Integrated Program in Neuroscience, McGill University, 3801 University Street, Room 141, Montreal, Que. H3A 2B4, Canada; Research Institute of the McGill University Health Centre, 2155 Guy Street, 5th Floor, Montreal, Que. H3H 2R9, Canada. Electronic address: bwhatley@dal.ca.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Whatley
authors.affiliation: Department of Neurology and Neurosurgery, McGill University, 845 Rue Sherbrooke Ouest, Montréal, Que., Canada; Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, Que. H3A 2B4, Canada. Electronic address: sridar.narayanan@mcgill.ca.
authors.forename: Sridar
authors.initials: S
authors.lastname: Narayanan
authors.affiliation: Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, Que. H3A 2B4, Canada. Electronic address: yves.lapierre@mcgill.ca.
authors.forename: Yves
authors.initials: Y
authors.lastname: Lapierre
authors.affiliation: Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, Que. H3A 2B4, Canada. Electronic address: douglas.arnold@mcgill.ca.
authors.forename: Douglas L
authors.initials: DL
authors.lastname: Arnold
authors.affiliation: Research Institute of the McGill University Health Centre, 2155 Guy Street, 5th Floor, Montreal, Que. H3H 2R9, Canada; Department of Neurology and Neurosurgery, McGill University, 845 Rue Sherbrooke Ouest, Montréal, Que., Canada. Electronic address: lisa.koski@mcgill.ca.
authors.forename: Lisa
authors.initials: L
authors.lastname: Koski
mesh_terms: D000328:Adult; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000175:diagnosis / Q000503:physiopathology*; D009433:Neural Inhibition / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods; D034941:Upper Extremity / Q000502:physiology*
keywords: Brain damage; Cortical silent period; Intracortical inhibition; Motor control; Multiple sclerosis; Transcranial magnetic stimulation