title: Discharge rates in electromyography distinguish early between peripheral and central paresis.
abstract: BACKGROUND
  Abnormally increased discharge rates (DRs) of motor unit potentials on concentric needle electromyography (CNEMG) indicate a loss of motor units in peripheral neurogenic lesions.
  
  
  METHODS
  To determine when increased DRs occur during the course of a peripheral nerve lesion, we retrospectively analyzed CNEMG recordings of 19 patients with acute weakness of peripheral origin.
  
  
  RESULTS
  The initial CNEMG studies took place from 3.7 hours to 10 days after the onset of the lesion. Abnormally increased DRs (≥20/s) were found in all but 1 of the muscles in which MRC grade was <4. Peripheral neurogenic damage was confirmed in all patients thereafter. The DRs depended on neither the kind of lesion nor the time between onset and CNEMG examination.
  
  
  CONCLUSIONS
  The measurement of DRs of motor unit potentials is helpful immediately after a sudden paresis of MRC grade 3 or worse to differentiate between a central and a peripheral lesion.
authors.affiliation: Department of Systems Neuroscience, University Medical Centre Hamburg-Eppendorf, Martinistrasse 52, D-20246 Hamburg, Germany. t.juergens@uke.de
authors.forename: Tim P
authors.initials: TP
authors.lastname: Jürgens
authors.forename: Christoph
authors.initials: C
authors.lastname: Puchner
authors.forename: Wilhelm J
authors.initials: WJ
authors.lastname: Schulte-Mattler
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D003937:Diagnosis, Differential; D004568:Electrodiagnosis / Q000379:methods*; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology*; D010291:Paresis / Q000175:diagnosis* / Q000503:physiopathology*; D012189:Retrospective Studies