title: The role of transcranial magnetic stimulation in evaluation of motor cortex excitability in Rett syndrome.
abstract: Rett syndrome (RTT) is a frequent neurodevelopmental disorder confirmed by clinical criteria and supported by the methyl-CpG-binding protein 2 gene (MECP2) mutation. A short central motor conduction time (CMCT) was reported in transcranial magnetic stimulation (TMS) studies performed in RTT. This was attributed to hyperexcitability of the motor cortex and/or spinal motor neurons, but was not studied further.
  
  
  OBJECTIVE
  We performed TMS in RTT to evaluate motor cortex excitability by determining the cortical motor threshold (CMT) and motor cortex inhibition by the cortical silent period (CSP) besides measuring CMCT.
  
  
  METHODS
  Single-pulse TMS was performed in 17 Rett patients, diagnosed by clinical criteria and MECP2 mutation testing, and the same number of healthy controls. The outcome measures were compared between RTT groups with different antiepileptic drugs (AED) and those with and without the MECP2 mutation.
  
  
  RESULTS
  CMCT was shorter, but we found elevated CMT and shorter CSP, which suggests decreased excitatory and inhibitory motor cortical function. The outcome was independent of AED and the presence or absence of the MECP2 mutation.
  
  
  CONCLUSIONS
  Decreased excitatory and inhibitory motor cortical function could explain the short CMCT, with higher stimulus intensities needed to excite pyramidal neurons.
authors.affiliation: University Medical Centre, Clinical Institute for Clinical Neurophysiology Zaloška 7, 1000 Ljubljana, Slovenia. Electronic address: natalija.krajnc@mf.uni-lj.si.
authors.forename: Natalija
authors.initials: N
authors.lastname: Krajnc
authors.affiliation: University Medical Centre, Clinical Institute for Clinical Neurophysiology Zaloška 7, 1000 Ljubljana, Slovenia.
authors.forename: Janez
authors.initials: J
authors.lastname: Zidar
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D000071080:Cortical Excitability / Q000502:physiology*; D004569:Electroencephalography; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D051783:Methyl-CpG-Binding Protein 2 / Q000235:genetics; D009044:Motor Cortex / Q000503:physiopathology*; D009154:Mutation; D015518:Rett Syndrome / Q000175:diagnosis / Q000235:genetics / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
chemical_list: C497392:MECP2 protein, human; D051783:Methyl-CpG-Binding Protein 2
keywords: Children; Excitability; Motor cortex; Rett syndrome; Transcranial magnetic stimulation