title: Assessing neuromuscular junction stability from stimulated EMG in children.
abstract: OBJECTIVE
  We present our 9-year experience of stimulated EMG potential analysis using concentric electrodes (SPACE) to evaluate neuromuscular junction (NMJ) disorders in awake children. The technique uses high frequency filtration of stimulated motor unit potentials and applies peak detection software to estimate mean consecutive difference (MCD).
  
  
  METHODS
  SPACE was carried out in orbicularis oculi of 878 children (377 girls; median age 47months) between 2007 and 2015, stimulating the facial nerve with a monopolar cathode. Mean MCD-index (MCD-I) was expressed as a ratio of the measured MCD to the upper normal limit. Diagnostic accuracy was calculated for primary NMJ disorders based on the 660 cases with clinical follow-up data.
  
  
  RESULTS
  Primary NMJ disorders were present in 106 children, including 46 with genetically confirmed congenital myasthenic syndrome (CMS). Mean MCD-I was two times higher in children with primary NMJ disorders compared to others (205±108μs vs 94±38μs, p<0.005). After excluding children with neuronopathies, an MCD-I >100% had 84% sensitivity and 74% specificity for the primary NMJ disorders. Receiver operating characteristics (ROC) curve identified an MCD-I >115% as providing best diagnostic accuracy with sensitivity of 77% and specificity of 84%.
  
  
  CONCLUSIONS
  SPACE is practicable and safe in unsedated children.
  
  
  CONCLUSIONS
  In combination with routine EMG, it has high diagnostic accuracy and can facilitate recognition of paediatric NMJ transmission disorders.
authors.affiliation: Department of Clinical Neurophysiology, Great Ormond Street Hospital for Children NHS Foundation Trust, London WC1N 3JH, United Kingdom. Electronic address: Matthew.Pitt@gosh.nhs.uk.
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Pitt
authors.affiliation: Department of Clinical Neurophysiology, Our Lady's Children's Hospital, Crumlin, Dublin 12, Ireland.
authors.forename: John C
authors.initials: JC
authors.lastname: Mchugh
authors.affiliation: Department of Clinical Neurophysiology, Great Ormond Street Hospital for Children NHS Foundation Trust, London WC1N 3JH, United Kingdom; Department of Clinical Neurophysiology, Queen's Hospital, Barking, Havering and Redbridge University Hospitals NHS Trust, London, United Kingdom.
authors.forename: Jacquie
authors.initials: J
authors.lastname: Deeb
authors.affiliation: Department of Clinical Neurophysiology, Great Ormond Street Hospital for Children NHS Foundation Trust, London WC1N 3JH, United Kingdom.
authors.forename: Ralph A
authors.initials: RA
authors.lastname: Smith
mesh_terms: D002648:Child; D002675:Child, Preschool; D004566:Electrodes; D004576:Electromyography / Q000295:instrumentation / Q000379:methods*; D019054:Evoked Potentials, Motor; D005154:Facial Nerve / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D009468:Neuromuscular Diseases / Q000175:diagnosis / Q000503:physiopathology*; D009469:Neuromuscular Junction / Q000503:physiopathology*; D012680:Sensitivity and Specificity
keywords: EMG; Jitter; Myasthenia; Neuromuscular junction; Paediatrics