Ascending Paralysis in A Young Adult Male: Nitrous Oxide-Induced Functional Vitamin B12 Deficiency Mimicking Guillain-Barré Syndrome

A 30-year-old male presented with progressive ascending weakness concerning for GBS. Neurologic examination revealed areflexia and sensory deficits. However, cerebrospinal fluid analysis and electromyography were inconsistent with GBS. Further history revealed frequent recreational use of nitrous oxide. Laboratory evaluation showed functional vitamin B12 deficiency. The patient improved with cessation of nitrous oxide and vitamin B12 supplementation. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: This case highlights the importance of considering metabolic and toxic mimics in patients presenting with acute flaccid paralysis. Emergency physicians should inquire about nitrous oxide use in young patients with atypical neurologic presentations, as timely diagnosis and treatment can prevent long-term neurologic damage.