The acute presentation of nitrous oxide-induced vitamin B-12 deficiency in a postoperative lumbar discectomy patient: illustrative case.

backgroundVitamin B-12 deficiency can cause serious hematological and neurological complications. While most cases are chronic, acute presentations may occur. In autoimmune diseases, pernicious anemia is a common cause of vitamin B-12 deficiency. The authors present a case of acute vitamin B-12 deficiency following nitrous oxide anesthesia in a patient with Graves' disease, highlighting the impact of preexisting autoimmune conditions on perioperative management. OBSERVATIONS: A 44-year-old African American male with Graves' disease presented with symptoms of an L5-S1 disc herniation and underwent an uncomplicated lumbar discectomy under nitrous oxide anesthesia with immediate symptom relief. In the early postoperative period, he developed gastrointestinal symptoms, a spastic myelopathy, and gait instability. Workup revealed severe vitamin B-12 deficiency, and his symptoms resolved with replacement therapy. LESSONS: The acute presentation of vitamin B-12 deficiency is rare but can lead to serious and potentially irreversible neurological consequences if not recognized. Unexpected acute symptoms in the perioperative period require prompt evaluation. Awareness of past medical history and perioperative exposures can help identify the cause. Early recognition and treatment enable favorable outcomes in vitamin B-12 deficiency. https://thejns.org/doi/10.3171/CASE25785.