Nitrous oxide-induced myeloneuropathy: a case series.

BACKGROUND: Nitrous 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. METHODS: We 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. 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 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). CONCLUSIONS: Preventable 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

Evaluation of an ambulatory care pathway for patients with nitrous oxide-induced myeloneuropathy.

Peer reviewed: TrueINTRODUCTION: Cases of nitrous oxide (N2O)-induced myeloneuropathy are increasing at UK hospitals. At our centre, a dedicated ambulatory care pathway, endorsed nationally, was established to treat and monitor patients with N2O-myeloneuropathy in 2021 and refined through three audit cycles. We analysed the outcomes of patients on this pathway to better understand factors associated with non-engagement. Alongside, a novel approach using WhatsApp for questionnaire delivery was trialled in an attempt to improve engagement with treatment. METHODS: Patients on the N2O ambulatory care pathway were identified from MDT meeting lists from 9 September 2022 to 25 April 2023. Clinical data were collected via electronic clinical records, including the most recent neurological examination and reason for discharge from the pathway. Patients identified from MDT lists from 27 January 2023 to 14 March 2023 were approached to participate in weekly 12-item surveys, delivered via WhatsApp. This was approved as a service development project with approval for WhatsApp use given by the chief clinical information officer. RESULTS: 35/56 (62.5%) patients were discharged from ambulatory care due to non-attendance and 17/56 (30.4%) completed their treatment course. The median time from initial presentation to discharge was 49 days. 24/40 (60.0%) of patients with a final neurological examination documented had a residual deficit, with objective sensory deficits most common. 12 patients were approached to receive weekly questionnaires via WhatsApp. 5/8 who expressed interest returned a consent form. All participants were withdrawn due to non-response or participant choice. 1/5 returned more than two surveys. CONCLUSION: Despite poor participation in surveys delivered via WhatsApp, novel approaches are needed to improve engagement with patients on the N2O ambulatory care pathway