title: Exploring the Evolution of Cortical Excitability Following Acute Stroke.
abstract: BACKGROUND
  Evolution of changes in intracortical excitability following stroke, particularly in the contralesional hemisphere, is being increasingly recognized in relation to maximizing the potential for functional recovery.
  
  
  OBJECTIVE
  The present study utilized a prospective longitudinal design over a 12-month period from stroke onset, to investigate the evolution of intracortical excitability involving both motor cortices and their relationship to recovery, and whether such changes were influenced by baseline stroke characteristics.
  
  
  METHODS
  Thirty-one patients with acute unilateral ischemic stroke were recruited from a tertiary hospital stroke unit. Comprehensive clinical assessments and cortical excitability were undertaken at stroke onset using a novel threshold-tracking paired-pulse transcranial magnetic stimulation technique, and repeated at 3-, 6-, and 12-month follow-up in 17 patients who completed the longitudinal assessment.
  
  
  RESULTS
  Shortly following stroke, short-interval intracortical inhibition (SICI) was significantly reduced in both lesioned and contralesional hemispheres that correlated with degree of recovery over the subsequent 3 months. Over the follow-up period, ipsilesional SICI remained reduced in all patient groups, while SICI over the contralesional hemisphere remained reduced only in the groups with cortical stroke or more baseline functional impairment.
  
  
  CONCLUSIONS
  The current study has demonstrated that evolution of intracortical excitability, particularly over the contralesional hemisphere, may vary between patients with differing baseline stroke and clinical characteristics, suggesting that ongoing contralesional network recruitment may be necessary for those patients who have significant disruptions to the integrity of ipsilesional motor pathways. Results from the present series have implications for the development of neuromodulatory brain stimulation protocols to harness and thereby facilitate stroke recovery.
authors.affiliation: Brain and Mind Research Institute, University of Sydney, New South Wales, Australia Prince of Wales Clinical School, University of New South Wales, New South Wales, Australia w.huynh@neura.edu.au.
authors.forename: William
authors.initials: W
authors.lastname: Huynh
authors.affiliation: Western Clinical School, University of Sydney, New South Wales, Australia.
authors.forename: Steve
authors.initials: S
authors.lastname: Vucic
authors.affiliation: Prince of Wales Clinical School, University of New South Wales, New South Wales, Australia.
authors.forename: Arun V
authors.initials: AV
authors.lastname: Krishnan
authors.affiliation: University of New South Wales, New South Wales, Australia.
authors.forename: Cindy S-Y
authors.initials: CS
authors.lastname: Lin
authors.affiliation: Brain and Mind Research Institute, University of Sydney, New South Wales, Australia.
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Kiernan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002545:Brain Ischemia / Q000503:physiopathology* / Q000534:rehabilitation; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D007839:Functional Laterality; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D011446:Prospective Studies; D012720:Severity of Illness Index; D020521:Stroke / Q000503:physiopathology*; D000071939:Stroke Rehabilitation; D062606:Tertiary Care Centers; D050781:Transcranial Magnetic Stimulation / Q000379:methods
keywords: plasticity; stroke; transcranial magnetic stimulation (TMS)