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Science News: An Appraisal of Electrodiagnostic Studies in Stiff Person Syndrome

NSEB.jpgSubmitted by: Betul Gundogdu, MD
Edited by: Elliot Bodofsky, MD

An Appraisal of Electrodiagnostic Studies in Stiff Person Syndrome, Yeubing Li and Namish Thakora
Journal Of Clinical Neuromuscular Disorders; Volume 22, Dec(2):84-89

Summary: This is a review of electrodiagnostic (EDX) findings for diagnosis of stiff person syndrome (SPS). The authors performed a literature review of EDX findings in SPS as well as an online survey of SPS among EDX labs accredited by the American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM). Additionally, they studied the simultaneous motor unit firing in selected groups of agonist and antagonist muscles among a small group of healthy subjects. Literature review suggested that exteroceptive reflex testing on NCS and continuous muscle unit activation (CMUA), or simultaneous agonist-antagonist activation on EMG are the most informative EDX techniques for SPS. Exteroceptive reflex recording can be performed in proximal and distal muscles of the extremities (biceps, triceps, abductor pollicis brevis, quadriceps, biceps femoris, tibialis anterior) as well as axial muscles. However, exteroceptive reflex testing is rarely used by AANEM accredited EDX laboratories. CMUA studies were mostly performed in thoracolumbar paraspinal or abdominal muscles. However, simultaneous voluntary coactivation of selected agonist and antagonist muscle groups (biceps-triceps, rectus femoris-semitendinosus, tibialis anterior-soleus) can be observed on EMG in healthy subjects. In conclusion, positive EDX findings may serve as supportive evidence, but has limitations in confirming the diagnosis SPS.

Comments: This article clarifies that based on the current evidence, EDX studies alone are not sufficient for a diagnosis of SPS. 

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