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Electrophysiology of Stiff-Person Spectrum Disorders

  • Pichet Termsarasab
  • Thananan Thammongkolchai
  • Bashar Katirji
Chapter
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Abstract

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.

Keywords

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

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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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