Vitamin B₁₂ deficiency-induced neuropathy secondary to prolonged recreational use of nitrous oxide

A 24-year-old female, otherwise healthy, presented to the Emergency Department (ED) with difficulty walking and bilateral leg pain. The patient was a recreational nitrous oxide (NO₂) user, also known as "whippets" or simply nitrous. Neurologic examination demonstrated an unsteady gait and positive Romberg sign along with normal deep tendon reflexes and normal muscle strength in upper and lower extremities. Laboratory results demonstrated macrocytic erythropoiesis, reduced B₁₂, elevated homocysteine, and elevated methylmalonic acid. Outpatient MRI later demonstrated degeneration of the posterior spinal column. The patient was empirically treated in the ED with intramuscular B₁₂ and admitted to the evaluation unit for pain control and Physical Therapy (PT) evaluation. Emergency Medicine (EM) physicians should be aware of this condition because NO₂ is used both recreationally and in medicine. With the popularity of recreational nitrous oxide, many emergency patients have experience with this drug. As in our case report, the toxic effects can be profound and mimic other emergent conditions like stroke. Emergency physicians should have a higher index of suspicion for the toxic effects of this common drug. Elderly, vegetarians and patients with Irritable Bowel Disease are at higher risk and may even experience toxicity from nitrous oxide used therapeutically during routine anesthesia.