Electromyography and nerve conduction studies can be very helpful in the diagnosis. Unfortunately, electrodiagnostic study findings can be completely normal in acute GBS, and normal results do not rule out GBS. However, repeat electromyography and nerve conduction studies in a few days should become diagnostic. Serum autoantibodies are not measured routinely in the workup of GBS, but results may be helpful in patients with a questionable diagnosis or a variant of GBS. MRI is sensitive but nonspecific for diagnosis. However, it can reveal nerve root enhancement and may be an effective diagnostic adjunct.
Most, but not all, patients with GBS have an elevated CSF protein level (> 400 mg/L), with normal CSF cell counts. Elevated or rising protein levels on serial lumbar punctures and 10 or fewer mononuclear cells/mm3 strongly support the diagnosis. A normal CSF protein level does not rule out GBS, however, as the level may remain normal in 10% of patients.
For more on the workup of GBS, read here.
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Cite this: Stephen Kishner. Fast Five Quiz: Test Your Knowledge of Guillain-Barré Syndrome - Medscape - Nov 02, 2016.