Nitrous oxide myelopathy with functional vitamin B 12 deficiency.

Recreational use of nitrous oxide as a 'legal high' is increasing in the UK. Physicians should be 'street wise' to this increasing prevalence and aware of the potential neurological complications which may result from misuse. We describe a 17-year-old male patient who presented to neurology with a severe myelopathy following prolonged recreational use of nitrous oxide. MRI demonstrated characteristic changes affecting the dorsal columns and blood tests demonstrated a 'functional' B12 deficiency. Clinical and radiological improvement was noted following initiation of vitamin B12 replacement. © BMJ Publishing Group Limited 2019. No commercial re-use. See rights and permissions. Published by BMJ.