Presentation A 16-year old male presented to hospital with limb numbness and unsteady gait. He had a background of chronic nitrous oxide misuse, prompting a possible diagnosis of subacute combined degeneration of the spinal cord (SCDC), an increasingly prevalent cause of the neurological disorder.

Diagnosis This diagnosis was confirmed with magnetic resonance imaging of the spine which demonstrated typical T2 hyperintensities in the posterior cervical and thoracic cord. Treatment As SCDC is caused by vitamin B12 deficiency, he was treated with intramuscular vitamin B12 injections. His gait and sensory symptoms improved within days.

Discussion Nitrous oxide or “laughing gas” is cheap and accessible making it an increasingly popular recreational drug in Ireland, particularly among teenagers. It is not a controlled substance despite its severe side effects including significant neurological complications.