The Last Laugh - Reversible myeloneuropathy induced by chronic nitrous oxide use.

A previously fit and well 19 year old male presents with a progressive ataxic - sensory neuropathy worsening over 2 - 3 weeks. History and investigations revealed extensive recreational use of nitrous oxide resulting in functional B12 deficiency and consequent subacute combined degeneration of the cord. Abstinence and B12 supplementation resulted in a rapid and full neurological recovery. This case report highlights the importance of considering nitrous oxide abuse in the differential diagnosis of atypical neurological symptoms and signs, and emphasizes the possibility of good clinical outcomes with treatment.