Severe myeloneuropathy from acute high-dose nitrous oxide (N2O) abuse.

BACKGROUND: Myeloneuropathy from chronic exposure to nitrous oxide has been described. Nitrous oxide irreversibly alters B(12) activation, causing signs and symptoms of B(12) deficiency. OBJECTIVES: We describe a case of myeloneuropathy secondary to acute use of high-dose nitrous oxide. CASE REPORT: A 24-year-old man presented to the Emergency Department complaining of numbness and tingling of his hands and feet, as well as worsening clumsiness and gait disturbances after escalating use of nitrous oxide in the prior 2 weeks. He was found to have dysmetria, poor proprioception, decreased sensation to vibration and light touch over his extremities, and a mildly positive Romberg sign. Laboratory test values revealed a normal B(12) level but increased methylmalonic acid and homocysteine levels. The patient was admitted to the hospital and started on a course of B(12) injections. He was discharged after 3 days with daily B(12) supplementation. CONCLUSIONS: This case demonstrates myeloneuropathic changes secondary to acute high-dose nitrous oxide exposure.