No laughing matter - Myeloneuropathy due to heavy chronic nitrous oxide abuse.

Chronic nitrous oxide abuse is a known cause of myeloneuropathy. Nitrous oxide irreversibly inactivates vitamin B12 causing demyelination of the dorsal spinal columns, clinically indistinguishable from that which is caused by vitamin B12 deficiency. We report a 37-year-old female who presented with ataxia, loss of lower extremity proprioception, demyelination of her cervical dorsal spinal columns, and other laboratory and physical exam findings consistent with nitrous oxide abuse. The patient reported daily use in excess of 500 nitrous oxide cartridges, also known as "whippits". Nitrous oxide myeloneuropathy should be included in the differential diagnoses for emergency medicine physicians when evaluating a patient with bilateral neurologic deficits and ataxia.