title: The spectrum of electrophysiological abnormalities in Bell's palsy.
abstract: BACKGROUND
  As part of an investigation of a suspected "outbreak" of Bell's palsy in the Greater Toronto Area, a population-based sample of patients with Bell's palsy was investigated electrophysiologically to help understand the spectrum of abnormalities that can be seen in this setting.
  
  
  METHODS
  Two hundred and twenty-four patients were surveyed, of whom 91 underwent formal neurological assessment. Of the latter, 44 were studied electrophysiologically using standard techniques. Thirty-two of the 44 patients fulfilled clinical criteria for Bell's palsy.
  
  
  RESULTS
  A wide range of electrophysiological changes was observed. Blink responses were the most useful test showing diagnostic sensitivity of 81% and specificity of 94% compared to the contralateral control side. Needle electromyography was additionally helpful in only one patient of six with normal conduction studies.
  
  
  CONCLUSIONS
  There is a wide spectrum of electrophysiological abnormalities in Bell's palsy. Blink reflex latencies may be under-utilized in the assessment of the facial nerve in Bell's palsy. Facial EMG is not generally useful in routine assessment.
authors.affiliation: Division of Neurology, St. Michael's Hospital, ON, Canada.
authors.forename: M D
authors.initials: MD
authors.lastname: Hill
authors.forename: G
authors.initials: G
authors.lastname: Midroni
authors.forename: W C
authors.initials: WC
authors.lastname: Goldstein
authors.forename: S L
authors.initials: SL
authors.lastname: Deeks
authors.forename: D E
authors.initials: DE
authors.lastname: Low
authors.forename: A M
authors.initials: AM
authors.lastname: Morris
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D020330:Bell Palsy / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology*; D001767:Blinking; D004576:Electromyography; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009431:Neural Conduction; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity