title: Repetitive facial nerve stimulation in myasthenia gravis 1min after muscle activation is inferior to testing a second muscle at rest.
abstract: OBJECTIVE
  To explore the increased diagnostic yield of repetitive nerve stimulation (RNS) following activation for myasthenia gravis (MG) diagnosis, and compare with testing an additional muscle at rest only.
  
  
  METHODS
  We performed a retrospective chart review of patients diagnosed with MG attending the neuromuscular clinic from 2013 to 2015 and extracted data on electrophysiological studies, including frequency of decrement of 10% or above, with facial RNS at rest, and following activation.
  
  
  RESULTS
  The total cohort included 102 patients with MG, 65 with generalized, and 37 with ocular MG. Facial RNS sensitivities for diagnosing MG were 32-46% and 14-19% respectively. The increase in RNS sensitivity following muscle activation was 6-8% for frontalis muscle recordings, and 0-2% for nasalis muscle recordings. Recording from both muscles at rest only, increased the sensitivity by 9-15%.
  
  
  CONCLUSIONS
  RNS is a valid method for confirming a clinical diagnosis of MG. The increased diagnostic yield of RNS following activation is controversial. Our study shows that the increased diagnostic yield of facial RNS following activation is modest, and is less than performing facial RNS in a second muscle.
  
  
  CONCLUSIONS
  Performing facial RNS in an additional muscle at rest appears to be more sensitive than facial RNS in a single muscle after activation.
authors: Ellen and Martin Prosserman Centre for Neuromuscular Diseases, Division of Neurology, Department of Medicine, University Health Network, University of Toronto, Toronto, Canada.
authors: Alon
authors: A
authors: Abraham
authors: Department of Neurology, King Fahad Hospital of the University, University of Dammam, Dammam, Saudi Arabia.
authors: Majed
authors: M
authors: Alabdali
authors: Department of Neurology, King Fahad Hospital of the University, University of Dammam, Dammam, Saudi Arabia.
authors: Abdulla
authors: A
authors: Alsulaiman
authors: Ellen and Martin Prosserman Centre for Neuromuscular Diseases, Division of Neurology, Department of Medicine, University Health Network, University of Toronto, Toronto, Canada.
authors: Ari
authors: A
authors: Breiner
authors: Ellen and Martin Prosserman Centre for Neuromuscular Diseases, Division of Neurology, Department of Medicine, University Health Network, University of Toronto, Toronto, Canada.
authors: Carolina
authors: C
authors: Barnett
authors: Ellen and Martin Prosserman Centre for Neuromuscular Diseases, Division of Neurology, Department of Medicine, University Health Network, University of Toronto, Toronto, Canada.
authors: Hans D
authors: HD
authors: Katzberg
authors: Ellen and Martin Prosserman Centre for Neuromuscular Diseases, Division of Neurology, Department of Medicine, University Health Network, University of Toronto, Toronto, Canada. Electronic address: vera.bril@utoronto.ca.
authors: Vera
authors: V
authors: Bril
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005152:Facial Muscles / Q000294:innervation*; D005154:Facial Nerve / Q000502:physiology* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000175:diagnosis* / Q000503:physiopathology; D004561:Transcutaneous Electric Nerve Stimulation / Q000379:methods*
keywords: Muscle activation; Repetitive nerve stimulation; Retrospective study; Single fiber electromyography