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

OBJECTIVE: 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. METHOD AND RESULTS: 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. CONCLUSION: Incorporating sural-sparing would improve the specificity of GBS electrodiagnosis; especially in difficult to diagnose regional subtypes of GBS.