The more common diagnostic pitfalls relate to distinguishing GBS from spinal cord or cauda equina syndromes. Acute (radiculo-) neuropathies related to nutritional deficiency, critical illness, haematological malignancy, infection or vasculitis are also occasional mimics.

Confusion also sometimes surrounds the concept of ascending weakness. As GBS is most often demyelinating, proximal weakness is usually found in an affected limb, and the typical progression is from legs to arms to cranial nerves and respiratory muscles – not from distal to proximal in individual limbs. Exceptions exist, but descending weakness (starting with the cranial musculature) should prompt thoughts of botulism, not GBS.