Abstract
Nitrous oxide (N(2)O) is generally used in the medical and food industries. However, it is sometimes illegally misused by young adults as a recreational drug. In either of these uses, functional vitamin B12 deficiency results in neurological implications, such as peripheral neuropathy and subacute combined degeneration (SACD). Here, we report a case of N(2)O-induced SACD, in which a diagnosis of functional B12 deficiency was made based on borderline normal serum vitamin B12 levels with elevated metabolites (methylmalonic acid and homocysteine). In this case, treatment with intramuscular (IM) vitamin B12 led to significant clinical improvement.