title: Interhemispheric asymmetries of motor cortex excitability in the postacute stroke stage: a paired-pulse transcranial magnetic stimulation study.
abstract: OBJECTIVE
  Changes in the intracortical inhibition (ICI) and facilitation (ICF) of motor cortex paired-pulse transcranial magnetic stimulation were reported in the affected (AH) and unaffected (UH) hemispheres of stroke patients and reflect some of the mechanisms related to motor cortex plasticity and different degrees of functional recovery. The interhemispheric differences of the ICI/ICF slopes have been found to have a nearly identical time course in the 2 hemispheres of healthy subjects, and whether such symmetry is modified after monohemispheric stroke has not yet been examined. Our goal was to investigate the interhemispheric asymmetries of the time course of ICI/ICF between the AH and UH of stroke patients in the postacute phase of recovery.
  
  
  METHODS
  ICI/ICF recovery curves to subthreshold-conditioning suprathreshold-test magnetic stimuli were recorded from the paretic and nonparetic hand muscles of 10 well-recovered stroke patients and compared with those of a population of 10 control subjects.
  
  
  RESULTS
  In the healthy subjects, ICI/ICF showed a symmetrical time evolution between the 2 hemispheres. In stroke patients, the ICI/ICF slopes were significantly different between the UH and AH; the intracortical inhibition was reduced in the AH and normal in the UH.
  
  
  CONCLUSIONS
  The defective AH ICI associated with the effective UH ICI could represent a marker of poststroke cortical plasticity implicated as a mechanism relevant to functional recovery. Analysis of the interhemispheric asymmetries of the ICI/ICF recovery curves might provide a valuable neurophysiological parameter in the prognosis and follow-up of patients with monohemispheric stroke.
authors.affiliation: Fondazione Santa Lucia IRCCS, Via Ardeantina, 306, 00179, Rome, Italy. P.Cicinelli@hsantalucia.it
authors.forename: Paola
authors.initials: P
authors.lastname: Cicinelli
authors.forename: Patrizio
authors.initials: P
authors.lastname: Pasqualetti
authors.forename: Marina
authors.initials: M
authors.lastname: Zaccagnini
authors.forename: Raimondo
authors.initials: R
authors.lastname: Traversa
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Oliveri
authors.forename: Paolo Maria
authors.initials: PM
authors.lastname: Rossini
mesh_terms: D000208:Acute Disease; D000368:Aged; D018450:Disease Progression; D004558:Electric Stimulation / Q000295:instrumentation; D004574:Electromagnetic Fields; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D007839:Functional Laterality; D006225:Hand / Q000502:physiology / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D009433:Neural Inhibition; D009473:Neuronal Plasticity / Q000502:physiology; D020127:Recovery of Function; D012016:Reference Values; D012684:Sensory Thresholds; D020521:Stroke / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation