• Jessica Redmond, Belinda Cruse, and Lynette Kiers.
• Department of Neurology, Royal Melbourne Hospital, Melbourne, Victoria, Australia.
• Intern Med J. 2022 May 1; 52 (5): 740-744.

BackgroundNeurological presentations resulting from nitrous oxide (N2 O) abuse are increasing in Australia and worldwide. Despite known neuropsychiatric sequelae, N2 O canisters remain readily available and its use unregulated.AimsTo examine the demographics, clinical and electrophysiological findings of patients presenting with neurological complications of N2 O abuse, and thus inform clinicians and public health decision-makers of the significant public health concerns of this increasing practice.MethodsConsecutive patients presenting to a tertiary referral metropolitan hospital were included in this series. Patients were identified by a search of discharge summaries of patients admitted with acute or subacute neuropathy or myelopathy and a history of N2 O abuse, and from the electrophysiology database.ResultsThirteen patients were identified, most presenting with subacute paraesthesia, sensory ataxia and lower limb weakness. Eleven had low serum vitamin B12 . Spinal magnetic resonance imaging was consistent with subacute combined degeneration in eight. Nerve conduction studies revealed a motor or sensorimotor axonal neuropathy (three with motor predominance). There was a bimodal demographic distribution consisting of socially isolated, international university students and local residents with a history of mental illness and polydrug abuse.ConclusionsRecreational N2 O use is an emerging health problem in Australia. International university students and patients with pre-existing mental illness or polydrug use appear to be at increased risk. A severe motor neuropathy may emerge following vitamin B12 replacement. Public health measures are required to limit the availability of N2 O and to educate adolescents and young adults about the potential for significant harm.© 2021 Royal Australasian College of Physicians.

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