A Case Report of Nitrous Oxide-induced Myelopathy: An Unusual Cause of Weakness in an Emergency Department

INTRODUCTION: Weakness is a common symptom that within itself does not indicate a specific diagnosis. Recreational inhalant use such as nitrous oxide (NO) may not often be disclosed. Additionally, professional or occupational history, such as being a dentist or dental assistant, should be determined because of higher reported rates of NO misuse.1 Nitrous oxide can cause vitamin B(12) deficiency and resulting neuropathy. Nitrous oxide toxicity can have a wide variation of presentations with or without laboratory abnormalities or remarkable imaging findings, which can further complicate a diagnosis of weakness secondary to NO use. CASE REPORT: A 33-year-old female presented to the emergency department with progressive bilateral leg numbness and objective weakness after repeated recreational NO use. After an extensive workup, she was found to have vitamin B(12) deficiency and an electromyography study consistent with myeloneuropathy, despite normal imaging. She was prescribed high-dose vitamin B(12) therapy and stopped using NO. One year after diagnosis, our patient maintained NO sobriety and had near-complete resolution of prior neurologic deficits. CONCLUSION: The use of recreational inhalant and the patient’s occupation should be considered when a patient presents with weakness. Obtaining vitamin B(12) and methylmalonic acid levels should be considered for diagnosis. However, NO-induced neuropathy can be seen in patients with normal vitamin B(12) and methylmalonic levels and patients do not always have abnormal imaging findings. The healthcare team should consider the varied presentations and findings of substance-induced conditions such as NO toxicity.