[A patient with leg numbness and micturition symptoms].

A 37-year-old man presented with an acute loss of sensibility and a gait disorder, caused by a vitamin B12 deficiency due to nitrous oxide use. A spinal cord MRI showed an inverted V sign. Repeated use of nitric oxide blocks the remethylation of homocysteine to methionine, which, in turn, leads to demyelination. Vitamin B12 deficiency, or signs of it in physical examination or diagnostic procedures, is rare in young and otherwise healthy individuals. Therefore, the use of nitrous oxide as a party drug must always be considered as a cause of the deficiency in this particular group of patients, particularly since the popularity of its use is rapidly increasing. Our patient was treated with intramuscular vitamin B12 injections, which significantly improved his gait disorder and sensory symptoms.