Brain and body disconnect: A retrospective case series of subacute combined degeneration of the spinal cord from chronic nitrous oxide use in Perth, Western Australia.

BACKGROUND:Chronic nitrous oxide (N2O) use causes inactivation of vitamin B12, resulting in neurological and psychiatric symptoms. This case series presents all N2O-related presentations to the emergency department at Royal Perth Hospital between June 2019 and June 2021, alongside the costs of these admissions. CASE PRESENTATION:Twenty-two patients were identified; 68% (n = 15) were male. The median age was 22.4 years (interquartile range [IQR], 20-30). Median daily number of N2O bulbs inhaled was 150 (IQR, 64-300) with a median duration of use of 9 months (IQR, 3-12). Presentations included ataxia, paraesthesia and falls (n = 18), urinary retention (n = 3) and psychotic symptoms (n = 2). Fourteen patients had severe symptoms prompting a magnetic resonance imaging of brain and spine, confirming 12 cases of subacute combined degeneration of the spinal cord. All patients had IMI vitamin B12 therapy, while 14 had oral methionine therapy. The median length of admission was 4 days (IQR 1-23 days). The median cost of admission per day for patients where costs were accessible (n = 7) was $2061 (IQR, $1903-$2860). DISCUSSION AND CONCLUSIONS:A case series of symptomatic chronic N2O use with severe neurological sequelae and significant costs associated per admission. Triangulation of emergency department and Ecstasy and Related Drugs Reporting System data helped prompt a swift public health response, including mandatory warning labels, limits to transaction amounts and legislative changes to the Medicines and Poisons Act to make it illegal for sale if there is a suspicion that it will be abused.