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GBS vs CIDP – Temporal Grey Zone — SCE Neurology MCQ

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ModeratePeripheral Neuropathy & NeuromuscularGBS vs CIDP – Temporal Grey ZoneSCE Neurology

A 50-year-old man presents with subacute progressive bilateral lower limb weakness and numbness ascending to the waist over 6 weeks. NCS show demyelinating changes in multiple nerves (prolonged DML, reduced CV, conduction block, temporal dispersion). CSF shows elevated protein (1.8 g/L) with 2 cells (albuminocytological dissociation). He is still progressing at 6 weeks. The onset was insidious rather than acute. What is the most likely diagnosis?

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Correct answer: A — Acute-onset CIDP — if symptoms progress beyond 8 weeks, the diagnosis is CIDP; this patient is in the diagnostic 'grey zone' between GBS and CIDP

The distinction between GBS and CIDP depends on the temporal course: GBS reaches nadir within 4 weeks (monophasic); CIDP has progression beyond 8 weeks (chronic). Patients progressing between 4–8 weeks are in a 'grey zone' — they may have GBS with prolonged progression, subacute inflammatory demyelinating polyneuropathy (SIDP), or acute-onset CIDP. If symptoms progress beyond 8 weeks, CIDP is diagnosed. This distinction is clinically important because CIDP requires long-term immunotherapy (IVIg, steroids, PLEX) rather than the single-course treatment of GBS. A: GBS reaches nadir within 4 weeks. C: MS does not cause peripheral demyelination. D: MND has normal NCS (motor axonal, but not demyelinating). E: Diabetic neuropathy is axonal.

Reference: EAN/PNS CIDP Guidelines (2021); EAN/PNS GBS Guidelines (2023)