Laboratory findings in GBS
What are the typical laboratory and electrophysiologic findings in Guillain Barre syndrome ?
Classically, the CSF in patients with GBS demonstrates cytoalbuminologic dissociation, though in the first week this may not have manifested.
CSF pleocytosis should bring to mind HIV, cytomegalovirus (CMV), Lyme disease, and sarcoid, lymphomatous, or carcinomatous polyradiculopathy.
NCVs are slowed in AIDP, but may be normal within the first two weeks of onset. In early AIDP, absent or prolonged H-reflexes and F-waves, prolonged distal CMAP duration, and/or temporal dispersion may be seen.
Conduction block and slowed velocities may be seen later. Conduction block accounts for most of the initial weakness, but after 2 to 3 weeks, axonal damage may contribute to weakness with EMG evidence of muscle denervation.
“Sural sparing” is a particular electrophysiologic finding seen in AIDP.
Sural sparing refers to the phenomenon of intact sural sensory responses but absent upper extremity sensory responses, which is atypical for more common length-dependent generalized polyneuropathies.
