Nitrous oxide-induced myeloneuropathy: a case series.

Background: Nitrous oxide (N ₂ O) is the second most common recreational drug used by 16- to 24-year-olds in the UK. Neurological symptoms can occur in some people that use N ₂ O recreationally, but most information comes from small case series.
Methods: We describe 119 patients with N ₂ O-myeloneuropathy seen at NHS teaching hospitals in three of the UK's largest cities: London, Birmingham and Manchester. This work summarises the clinical and investigative findings in the largest case series to date.
Results: Paraesthesia was the presenting complaint in 85% of cases, with the lower limbs more commonly affected than the upper limbs. Gait ataxia was common, and bladder and bowel disturbance were frequent additional symptoms. The mid-cervical region of the spinal cord (C3-C5) was most often affected on MRI T2-weighted imaging. The number of N ₂ O canisters consumed per week correlated with methylmalonic acid levels in the blood as a measure of functional B ₁₂ deficiency (rho (ρ)=0.44, p=0.04).
Conclusions: Preventable neurological harm from N ₂ O abuse is increasingly seen worldwide. Ease of access to canisters and larger cylinders of N ₂ O has led to an apparent rise in cases of N ₂ O-myeloneuropathy in several areas of the UK. Our results highlight the range of clinical manifestations in a large group of patients to improve awareness of risk, aid early recognition, and promote timely treatment.
Competing Interests: Competing interests: DM leads a medical student-run unpaid campaign - ‘N2O: Know The Risks’ - which provides educational teaching sessions on the risks of nitrous oxide in East London.
(© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)