SUBACUTE COMBINED DEGENERATION OF THE SPINAL CORD SECONDARY TO NITROUS OXIDE-INDUCED B12 DEFICIENCY

A previously healthy adolescent male was admitted with paraesthesia of his arms and legs. He admitted to daily recreational nitrous oxide use for the previous 3–4 months. He was found to have severe vitamin B12 deficiency, while magnetic resonance imaging of his spine showed T2 hyperintensity within the dorsal columns. This was suggestive of subacute combined degeneration of the spinal cord. He was treated with intramuscular injections of hydroxocobalamin and showed moderate improvement 1 month post-discharge. LEARNING POINTS: It is important to take a full history of illicit drug use, especially in young patients presenting with unusual symptoms. In cases of suspected nitrous oxide-induced neurological dysfunction with normal vitamin B12 levels, serum levels of methylmalonic acid and homocysteine can be measured to aid diagnosis. Prompt treatment of nitrous oxide-induced subacute combined degeneration of the spinal cord with B12 injections and discontinuation of nitrous oxide use allow for a gradual recovery, although in some cases patients may be left with residual symptoms.