Published in the Irish Journal of Medical Science, a new study highlights the growing neurological consequences of recreational nitrous oxide abuse, particularly among young adults.

Subacute combined degeneration of the cord (SACD) is traditionally associated with vitamin B12 deficiency and affects the posterior and lateral columns of the spinal cord. Nitrous oxide inactivates vitamin B12 by oxidising its cobalt ion, impairing critical metabolic pathways necessary for myelin integrity. This results in neurological dysfunction, often presenting as a myeloneuropathy. A recent single-centre case series study examined nitrous oxide-induced myeloneuropathy in patients presenting to Tallaght University Hospital in Dublin between October 2022 and July 2024.1

The study identified 18 patients with nitrous oxide-induced myeloneuropathy over a 21-month period. The cohort had a mean age of 20 years (range 16–24), and 78% were male. Most patients (aged 16 -18) reported episodic use of nitrous oxide, using up to 12 large cannisters (typically a 580 g cannister) at various levels of regularity, over periods varying from one month to several years. Clinically, the most common presenting symptom was paraesthesia (83%), followed by limb weakness (72%) and gait impairment (44%). Examination frequently revealed sensory ataxia, impaired joint position sense and vibration sense, distal weakness, and reduced or absent reflexes. Severe cases required inpatient rehabilitation due to functional disability.

Laboratory investigations showed that while only a minority had clearly low serum vitamin B12 levels, most had low-normal levels or had already received supplementation. Importantly, homocysteine levels were elevated in nearly all patients tested, including some with normal B12 levels, supporting the concept of functional B12 deficiency. Methylmalonic acid was also elevated in many cases. Magnetic resonance imaging of the spinal cord demonstrated T2 hyperintensity in the cervical dorsal columns in approximately one-half of patients, sometimes extending into the thoracic cord.

The authors note that data from the Global Drugs Survey2 demonstrate increasing recreational nitrous oxide use, particularly among young people. However, despite growing awareness of its risks, many patients in this cohort continued using nitrous oxide even after experiencing complications. The ready availability of large cannisters, often marketed for catering purposes, contributes to ease of access and potentially to underestimation of harm.

The study concludes that nitrous oxide-induced myeloneuropathy represents a significant and ongoing public health concern in Ireland. Early recognition is critical, as prompt vitamin B12 treatment can prevent permanent disability. The authors emphasise the need for continued physician awareness, public education, and potentially broader legislative or cross-sectoral responses to address rising misuse and its neurological consequences. 

1    Redmond A, Samuel S, Ryan M et al. (2025) Nitrous oxide abuse: single centre experience of nitrous oxide induced myeloneuropathy. Ir. J. Med. Sci. Available from: https://www.drugsandalcohol.ie/44736/

2    Winstock A, Maier L.J, Zhuparrism A et al. (2021) Global drug survey (GDS) 2021 key findings report. London: Global Drug Survey. Available from: https://www.drugsandalcohol.ie/35257/