423 - A Case Report of Nitrous Oxide Inhalant- Induced Vitamin B12 Deficiency

Thursday, February 22, 2024

5:00 PM – 6:30 PM EDT

Presenting Author(s)

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Paul Mgbam, MD

Resident Physician
Stanford University
Redwood City, California, United States

Corresponding Author(s)

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phalgun nori, MD

associate chief of brain injury
santa clara valley medical center
san jose, California, United States

Co-Author(s)

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Andre Arabe, BS

Medical Student
Lake Erie College of Osteopathic Medicine
Santa Cruz, California, United States

Case Diagnosis: Nitrous Oxide Induced Subacute Combined Degeneration

Case Description: A 42-year-old female with history of hypothyroidism, depression presented to the hospital July 2023 with progressively worsening paresthesias of her hands and feet over one year, with acute worsening over one week during which patient was using 200 Nitrous Oxide (NO) inhalants daily. Of note patient had bilateral upper & lower extremity NCS approximately 6 months prior to hospitlization that were normal. The patient felt increasing gait instability due to paresthesia in her feet and was unable to ambulate without assistance. She denied headaches, neck pain, saddle anesthesia, or urinary/bowel incontinence. Exam findings were positive for diminished pain sensation in bilateral upper extremities and gross decreased sensation at bilateral distal upper/lower extremities. Lab findings demonstrated vitamin B12 deficiency (< 159 pg/mL) with mild macrocytic anemia. MRI imaging of the brain and spine did not show any white matter or cord lesions.

Discussions: Nitrous oxide is a colorless gas often used for anesthesia in dental/surgical procedures. According to the 2020 National Survey on Drug Use and Health, NO abuse among adults 18 and over was 5.1%. NO abuse can cause Vitamin B12 (cyanocobalamin) deficiency causing myelopathy or subacute combined degeneration, and psychiatric effects. NO causes inactivation of vitamin B12, which is used as a cofactor for methionine synthase an enzyme used to produce methionine. Methionine is a precursor to S-adenosyl methionine which is used as a methyl donor to maintain integrity of myelin sheath.

Conclusions: The use of nitrous oxide inhalants has been on the rise domestically (Karr et. al 2016). Clinical suspicion for inhalant use should be high in patients with vitamin B12 deficiency (symptoms including paresthesias, ataxic gait). Given the volume of these patients requiring neurorehabilitation, physiatrists should be aware of the impact of this condition and providing adequate psychosocial support for these patients.