Nitrous oxide-induced neurological disorders: an increasing public health concern

Background Neurological presentations resulting from nitrous oxide (N2O) abuse are increasing in Australia and worldwide. Despite known neuropsychiatric sequelae, N2O canisters remain readily available and its use unregulated. Aims To examine the demographics, clinical and electrophysiological findings of patients presenting with neurological complications of N2O abuse, and thus inform clinicians and public health decision-makers of the significant public health concerns of this increasing practice. Methods Consecutive 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 N2O abuse, and from the electrophysiology database. Results Thirteen patients were identified, most presenting with subacute paraesthesia, sensory ataxia and lower limb weakness. Eleven had low serum vitamin B-12. 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. Conclusions Recreational N2O 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 B-12 replacement. Public health measures are required to limit the availability of N2O and to educate adolescents and young adults about the potential for significant harm.