Myasthenia gravis (MG): neurophysiology

Evidence-based neurology checklist on myasthenia gravis (mg): neurophysiology: Repetitive nerve stimulation (RNS) This measures the muscle response to supramaximal nerve stimulation at 2-3 Hz A positive result is a 10% decremental response The abductor pollicis brevis (APB) is more likely to be…

Repetitive nerve stimulation (RNS)

  • This measures the muscle response to supramaximal nerve stimulation at 2-3 Hz
  • A positive result is a 10% decremental response
  • The abductor pollicis brevis (APB) is more likely to be positive
  • The adductor digiti minimi (ADM) and he first dorsal interosseous (FDI) may be normal
  • Bilateral testing of at least 3 muscles may increase the sensitivity of the test

Single-fiber electromyography (SFEMG)

Causes of false positive single-fiber electromyography (SFEMG)

References

  1. Sanders DB, Howard JF, Johns TR. Single-fiber electromyography in myasthenia gravis. Neurology 1979; 29:68–76.
  2. Oh SJ, Kim DE, Kuruoglu R, Bradley RJ, Dwyer D. Diagnostic sensitivity of the laboratory tests in myasthenia gravis. Muscle Nerve 1992; 15:720–724.
  3. Matsumoto H, Akahori T, Yasaka K, Unuma A, Hashida H. Dissociated findings of repetitive nerve stimulation test among intrinsic hand muscles in myasthenia gravis. Neurol Clin Neurosci 2016; 4:233-235.
  4. Bou Ali H, Salort-Campana E, Grapperon AM, et al. New strategy for improving the diagnostic sensitivity of repetitive nerve stimulation in myasthenia gravis. Muscle Nerve 2017; 55:532-538. 
  5. Baruca M, Leonardis L, Podnar S, et al. Single fiber EMG as a prognostic tool in myasthenia gravis. Muscle Nerve 2016; 54:1034-1040. 
  6. And 2 more. Subscribe to see the full list

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