• Devan Mair, Alvar Paris, Safiya A Zaloum, Laura M White, Katherine C Dodd, Christina Englezou, Farhin Patel, Siraj Abualnaja, James B Lilleker, David Gosal, Tom Hayton, Di Liang, Holger Allroggen, Mark Pucci, Stephen Keddie, and Alastair J Noyce.
• Queen Mary University of London Barts and The London School of Medicine and Dentistry, London, UK.
• J. Neurol. Neurosurg. Psychiatr. 2023 Sep 1; 94 (9): 681688681-688.

BackgroundNitrous oxide (N2O) 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 N2O recreationally, but most information comes from small case series.MethodsWe describe 119 patients with N2O-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.ResultsParaesthesia 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 N2O canisters consumed per week correlated with methylmalonic acid levels in the blood as a measure of functional B12 deficiency (rho (ρ)=0.44, p=0.04).ConclusionsPreventable neurological harm from N2O abuse is increasingly seen worldwide. Ease of access to canisters and larger cylinders of N2O has led to an apparent rise in cases of N2O-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.© 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.

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