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.