title: The Mirror Illusion Increases Motor Cortex Excitability in Children With and Without Hemiparesis.
abstract: Mirror therapy provides a visual illusion of a normal moving limb by using the mirror reflection of the unaffected arm instead of viewing the paretic limb and is used in rehabilitation to improve hand function. Little is known about the mechanism underlying its effect in children with hemiparesis.
  
  
  
  To investigate the effect of the mirror illusion (MI) on the excitability of the primary motor cortex (M1) in children and adolescents.
  
  
  
  Twelve patients with hemiparesis (10-20 years) and 8 typically developing subjects (8-17 years) participated. Corticospinal reorganization was classified as contralateral (projection from contralateral hemisphere to affected hand) or ipsilateral (projection from ipsilateral hemisphere to affected hand). M1 excitability of the hemisphere projecting to the affected (nondominant in typically developing subjects) hand was obtained during 2 different conditions using single-pulse transcranial magnetic stimulation (TMS). Each condition (without/with mirror) consisted of a unimanual and a bimanual task. Motor-evoked potentials (MEPs) were recorded from the abductor pollicis brevis and flexor digitorum superficialis muscles.
  
  
  
  MEP amplitudes were significantly increased during the mirror condition ( P = .005) in typically developing subjects and in patients with contralateral reorganization. No significant effect of MI was found in subjects with ipsilateral reorganization. MI increased M1 excitability during active movements only. This increase was not correlated to hand function.
  
  
  
  MI increases the excitability of M1 in hemiparetic patients with contralateral corticospinal organization and in typically developing subjects. This finding provides neurophysiological evidence supporting the application of mirror therapy in selected children and adolescents with hemiparesis.
authors.affiliation: 1 Division of Neuropaediatrics, Development and Rehabilitation, University Children's Hospital Bern, Inselspital, Bern University Hospital, University of Bern, Switzerland.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Grunt
authors.affiliation: 2 Paediatric Neurology and Neurorehabilitation Unit, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Newman
authors.affiliation: 1 Division of Neuropaediatrics, Development and Rehabilitation, University Children's Hospital Bern, Inselspital, Bern University Hospital, University of Bern, Switzerland.|3 Institute of Human Movement Sciences and Sport, ETH Zürich, Switzerland.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Saxer
authors.affiliation: 1 Division of Neuropaediatrics, Development and Rehabilitation, University Children's Hospital Bern, Inselspital, Bern University Hospital, University of Bern, Switzerland.
authors.forename: Maja
authors.initials: M
authors.lastname: Steinlin
authors.affiliation: 4 University Institute of Diagnostic and Interventional Neuroradiology, University Hospital, Bern, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Weisstanner
authors.affiliation: 5 University Clinic of Neurology, University Hospital, Bern, Switzerland.|6 Neurocenter of Southern Switzerland, Ospedale Civico, Lugano, Switzerland.
authors.forename: Alain
authors.initials: A
authors.lastname: Kaelin-Lang
mesh_terms: D000293:Adolescent; D002648:Child; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006225:Hand / Q000503:physiopathology*; D006801:Humans; D007088:Illusions; D008297:Male; D009043:Motor Activity / Q000502:physiology; D009044:Motor Cortex / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000503:physiopathology; D009473:Neuronal Plasticity / Q000502:physiology; D010291:Paresis / Q000503:physiopathology* / Q000534:rehabilitation*; D026741:Physical Therapy Modalities; D050781:Transcranial Magnetic Stimulation; D016896:Treatment Outcome; D055815:Young Adult
keywords: cerebral palsy; hemiplegia; mirror illusion; pediatric rehabilitation; transcranial magnetic stimulation