The utility of sural-sparing pattern in the electrodiagnosis of regional subtypes of Guillain-Barré Syndrome

• Published in: Clinical neurophysiology practice 2020-01, Vol.5, p.43-45
• Main Authors: Umapathi, Thirugnanam, Koh, Jasmine S., Cheng, Y.J., Goh, Eunice J.H., Lim, Christen S.J.
• Format: Article
• Language: English
• Subjects: Clinical and; Electrodiagnosis; Guillain-Barré syndrome; Nerve conduction study; Sural-sparing pattern
• ISSN: 2467-981X; 2467-981X
• DOI: 10.1016/j.cnp.2019.12.002

•Sural-sparing pattern is an electrodiagnostic footprint of Guillain-Barré Syndrome.•Sural-sparing pattern helps in diagnosis of GBS, including regional subtypes.•It is likely due to predilection of upper limb nerves for subclinical entrapment. We present an exemplar patient, illustrating utility of the sural-sparing pattern in diagnosis of Guillain-Barré Syndrome (GBS). We then present data that sheds light on the pathophysiology of sural-sparing. We describe a case of complex ophthalmoplegia that exemplifies the challenge of diagnosing regional subtypes of Guillain-Barré Syndrome, and the value of scrutinizing sensory nerve action potentials for the sural-sparing pattern. We also demonstrate, in a series of GBS patients, how serial nerve conduction studies can reveal “covert” sural-sparing in patients without sural-sparing on the initial study. Finally, by studying the median and radial sensory nerve action potentials at digit I in GBS patients, we demonstrate that the likely pathology of sural-sparing is related to the predilection of median nerve for subclinical entrapment; where the blood-nerve barrier is deficient and therefore more exposed to the immunopathology of GBS. Incorporating sural-sparing would improve the specificity of GBS electrodiagnosis; especially in difficult to diagnose regional subtypes of GBS.