title: Motor cortex excitability in attention-deficit hyperactivity disorder (ADHD): A systematic review and meta-analysis.
abstract: BACKGROUND
  The core characteristic of attention deficit hyperactivity disorder (ADHD) is a persistent pattern of inattention and/or hyperactivity-impulsivity that causes developmental or functional impairment. Observational studies have investigated neurophysiological features in individuals with ADHD using transcranial magnetic stimulation (TMS) to identify which intracortical mechanisms are associated with the symptoms. This systematic review aimed to assess the quality of these studies and present meta-analyses of the available neurophysiological measures.
  
  
  METHODS
  This systematic review searched the PubMed, Scopus, Web of Science, with no date restrictions. The methodological quality of observational studies was assessed utilizing the Agency for Healthcare Research and Quality (AHRQ) criteria for observational studies. The analysis of the mean and standard deviation of the neurophysiological measurements was performed using the RevMan software version 5.0 for the meta-analyses of studies.
  
  
  RESULTS
  Nine publications that met the inclusion criteria were evaluated. Most of the AHRQ criteria were satisfied, indicating the good quality of the studies. On comparing subjects with ADHD and controls, the forest plot profiles were similar in respect to the resting motor threshold (RMT), and silent period (SP) but a significant difference was found for short intracortical inhibition (SICI).
  
  
  CONCLUSIONS
  This meta-analysis found reduced SICI in individuals with ADHD, when compared with controls. Given the small number of studies, it is important that further studies be conducted for a more robust conclusion to be formed.
authors.affiliation: Applied Neuroscience Laboratory, Department of Physical Therapy, Universidade Federal de Pernambuco, Recife, Pernambuco, Brazil.
authors.forename: T G
authors.initials: TG
authors.lastname: Dutra
authors.affiliation: Applied Neuroscience Laboratory, Department of Physical Therapy, Universidade Federal de Pernambuco, Recife, Pernambuco, Brazil.
authors.forename: A
authors.initials: A
authors.lastname: Baltar
authors.affiliation: Applied Neuroscience Laboratory, Department of Physical Therapy, Universidade Federal de Pernambuco, Recife, Pernambuco, Brazil. Electronic address: monte.silvakk@gmail.com.
authors.forename: K K
authors.initials: KK
authors.lastname: Monte-Silva
mesh_terms: D001289:Attention Deficit Disorder with Hyperactivity / Q000503:physiopathology*; D016022:Case-Control Studies; D019054:Evoked Potentials, Motor; D006801:Humans; D009044:Motor Cortex / Q000503:physiopathology*; D009433:Neural Inhibition; D050781:Transcranial Magnetic Stimulation
keywords: Attention deficit hyperactivity disorder; Cortical excitability; Transcranial magnetic stimulation