Use nutritional history, nitrous oxide exposure, and lack of anemia to keep B12-related myelopathy on the differential and avoid missing a reversible cause. Document the lesion level and the management step it implies.

Vitamin B12 deficiency is the classic reversible cause of myelopathy; Vitamin E deficiency and folate deficiency can mimic B12-related spinal cord disease; Nitrous oxide can precipitate rapid B12 inactivation and myelopathy; HIV vacuolar myelopathy and adrenoleukodystrophy belong in the differential; B12-related disease can involve both the CNS and PNS without anemia