Inhaled nitrous oxide-induced functional B12 deficiency.

Recreational nitrous oxide (N2O) is commonly used among young people partly due to its low cost and accessibility, and awareness of its potential adverse effects is poor in this group. One such adverse effect is degeneration of the spinal cord due to its disruption of DNA synthesis by inactivating cobalamin (B12).A 19-year-old man presented to the emergency department with a 4-week history of worsening paraesthesia in his fingers and lower limbs, and weakness in the hands and lower limbs for 2 weeks. On examination, he had an ataxic gait, reduced power of grip strength and ankle movements, and impaired sensation in the lower limbs. An MRI brain and spine revealed myelopathy of the cervical and thoracic cord.On further questioning, he reported recreational N2O inhalation. His symptoms improved after stopping this and he was treated with supplementation of B vitamins. Education strategies regarding the risks of N2O misuse are indicated.