How is single-fiber electromyography used in the workup of Lambert-Eaton myasthenic syndrome (LEMS)?

Updated: May 23, 2019
  • Author: David E Stickler, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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The jitter and blocking measured by single-fiber EMG is increased markedly in LEMS, frequently out of proportion to the severity of weakness. In many endplates, jitter and blocking decrease as the firing rate increases. This pattern is not seen in all endplates or in all patients with LEMS.

Because jitter and blocking may also decrease at higher firing rates in some endplates of patients with MG, this pattern does not confirm an LEMS diagnosis unless it is dramatic and seen in most muscles.

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