Electrophysiology of Stiff-Person Spectrum Disorders

  • Pichet Termsarasab
  • Thananan Thammongkolchai
  • Bashar Katirji


The diagnosis of stiff-person spectrum disorders (SPSD) is challenging because the clinician has to rely on patient history and high index of suspicion, particularly since muscle stiffness may accompany several other conditions. Electrophysiology had been used to support the diagnosis; however, this has several limitations. Routine EMG is mostly performed to exclude other causes such as Isaacs syndrome and myotonic disorders. In SPSD, continuous motor unit activity (CMUA) is described which is a persistent normal motor unit action potential activation, despite an attempt to relax. However, CMUA does not differ from normal motor unit activity seen in normal subject with poor relaxation. The electromyographer has to be cautious when evaluating SPSD by using EMG alone because making the diagnosis remains to be dependent on clinical presentation and antibody testing. Other electrophysiological modalities that test the hyperexcitation of spinal cord can be used but are not popular or readily available.


Stiff-person syndrome Electromyography EMG Electrophysiology Continuous motor unit activity CMU 


  1. 1.
    Katirji B. The scope of the EMG examination. In: Electromyography in clinical practice: a case study approach. 3rd ed. New York: Oxford University Press; 2018. p. 3.Google Scholar
  2. 2.
    Preston DC, Shapiro BE. Basic electromyography: analysis of motor unit action potential. In: Electromyography and neuromuscular disorders: clinical-electrophysiologic correlations. 3rd ed. London/New York: Elsevier Saunders; 2013. p. 247.Google Scholar
  3. 3.
    Erkelens CJ, Bosman F. Reflex sensitivity of human jaw-closing muscles during the silent period following a jaw jerk. Arch Oral Biol. 1983;28(11):1059–65. Scholar
  4. 4.
    Poncelet AN. Blink reflexes and the silent period in tetanus. Muscle Nerve. 2000;23(9):1435–8.<1435::aid-mus17>;2-i.CrossRefPubMedGoogle Scholar
  5. 5.
    Valls-Sole J. The blink reflex and other cranial nerve reflexes. In: Aminoff MJ, editor. Aminoff’s electrodiagnosis in clinical neurology. 6th ed. Philadelphia: Saunders; 2012. p. 426.Google Scholar
  6. 6.
    Moersch FP, Woltman HW. Progressive fluctuating muscular rigidity and spasm (“stiff-man” syndrome); report of a case and some observations in 13 other cases. Proc Staff Meet Mayo Clin. 1956;31(15):421–7.PubMedGoogle Scholar
  7. 7.
    Folli F, Prioletta A, Quattrini A, Galardi G. Stiff-man syndrome. In: Katirji B, Kaminski HJ, Ruff RL, editors. Neuromuscular disorders in clinical practice. 2nd ed. New York: Springer; 2014. p. 1465–77.CrossRefGoogle Scholar
  8. 8.
    Dalakas MC. Stiff person syndrome: advances in pathogenesis and therapeutic interventions. Curr Treat Options Neurol. 2009;11(2):102–10.CrossRefGoogle Scholar
  9. 9.
    Adler CH, Crews D, Hentz JG, Smith AM, Caviness JN. Abnormal co-contraction in yips-affected but not unaffected golfers: evidence for focal dystonia. Neurology. 2005;64(10):1813–4. Scholar
  10. 10.
    Farmer SF, Sheean GL, Mayston MJ, Rothwell JC, Marsden CD, Conway BA, et al. Abnormal motor unit synchronization of antagonist muscles underlies pathological co-contraction in upper limb dystonia. Brain. 1998;121(Pt 5):801–14. Scholar
  11. 11.
    Gorkovenko AV, Sawczyn S, Bulgakova NV, Jasczur-Nowicki J, Mishchenko VS, Kostyukov AI. Muscle agonist-antagonist interactions in an experimental joint model. Exp Brain Res. 2012;222(4):399–414. Scholar
  12. 12.
    Li Y, Thakore N. An appraisal of electrodiagnostic studies in stiff person syndrome. J Clin Neuromusc Dis. In press.Google Scholar
  13. 13.
    Espay AJ, Chen R. Rigidity and spasms from autoimmune encephalomyelopathies: stiff-person syndrome. Muscle Nerve. 2006;34(6):677–90. Scholar
  14. 14.
    Rakocevic G, Floeter MK. Autoimmune stiff person syndrome and related myelopathies: understanding of electrophysiological and immunological processes. Muscle Nerve. 2012;45(5):623–34. Scholar
  15. 15.
    Meinck HM, Ricker K, Hulser PJ, Solimena M. Stiff man syndrome: neurophysiological findings in eight patients. J Neurol. 1995;242(3):134–42. Scholar
  16. 16.
    Martinelli P, Nassetti S, Minardi C, Macri S, Ippoliti M. Electrophysiological evaluation of the stiff-man syndrome: further data. J Neurol. 1996;243(7):551–3. Scholar
  17. 17.
    Sandbrink F, Syed NA, Fujii MD, Dalakas MC, Floeter MK. Motor cortex excitability in stiff-person syndrome. Brain. 2000;123(Pt 11):2231–9. Scholar

Copyright information

© Springer Nature Switzerland AG 2020

Authors and Affiliations

  • Pichet Termsarasab
    • 1
  • Thananan Thammongkolchai
    • 1
  • Bashar Katirji
    • 2
  1. 1.Division of NeurologyFaculty of Medicine Ramathibodi Hospital, Mahidol UniversityBangkokThailand
  2. 2.Department of NeurologyUniversity Hospitals Cleveland Medical Center, Case Western Reserve UniversityClevelandUSA

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