When Euphoria Turns to Neuropathy: Vitamin B12 Deficiency Related to Nitrous Oxide

Background: Nitrous oxide is a widely abused inhalant known for its rapid onset of euphoric sensations. Chronic use, however, can result in functional vitamin B12 deficiency, causing megaloblastic anemia, peripheral neuropathy, and subacute combined degeneration (SCD) of the spinal cord. Case Presentation: This case report examines a 43-year-old male with a history of attention-deficit/hyperactivity disorder (ADHD) and chronic back pain, who presented with neurological symptoms secondary to chronic nitrous oxide use, subsequent B12 deficiency. The patient reported a one week history of lower extremity swelling, paresthesias, and vertigo. He admitted to daily nitrous oxide use for the past month. Neurological examination revealed ataxia, impaired proprioception, and a positive Romberg test. Laboratory studies showed macrocytic anemia and a severely decreased B12 level. MRI of the cervical spine revealed T2 hyperintensity in the dorsal columns, consistent with SCD. He was treated with intramuscular B12 and advised to discontinue nitrous oxide use. At a three-month follow-up, significant neurological improvement was noted, allowing him to return to work. Conclusion: Chronic nitrous oxide use can lead to functional B12 deficiency and subacute combined degeneration, a potentially reversible condition if treated early. Differential diagnoses include pernicious anemia, malabsorption syndromes, and other neurological disorders. Prompt diagnosis through serum B12, methylmalonic acid, homocysteine levels, and spinal imaging is essential to prevent permanent neurological damage. Nitrous oxide abuse is an emerging cause of B12 deficiency. Early recognition and intervention are essential for recovery. Healthcare providers should consider B12 deficiency in patients presenting with neurological symptoms and a history of nitrous oxide use.