Nitrous oxide abuse resulting in sub-acute combined degeneration of the spinal cord

Abstract

INTRODUCTION: Nitrous oxide (N2O) is widely used as a recreational drug and most users regard it as an innocuous substance ¹ although sustained use of N2O can have significant adverse neurological effects due to the inactivation of vitamin B12 ². This is a case of a previously fit and healthy 33 year old health professional who developed sub-acute combined degeneration of the spinal cord secondary to repeated N2O use. CASE PRESENTATION: A 33 year old man presented with deterioration in mental state over one month. There were concerns that he was developing a mood disorder and he was admitted to the mental health inpatient unit. However, early in his admission, a recent history of heavy N2O abuse was disclosed - the patient had been using the internet to source large quantities of N2O canisters. His substance use accounted for the change in his mental state. Neurological deficits, which were in keeping with N2O toxicity, were also noted including confusion, ataxia and impaired proprioception. MRI confirmed diffuse cord signal abnormality in the dorsal columns. MANAGEMENT AND OUTCOME: Following initial management at the mental health inpatient unit, he was subsequently transferred to a medical ward. He was commenced on regular intramuscular B12 injections which continued for several weeks. He had intensive input from physiotherapy, occupational therapy and neurology. There was robust family support throughout his admission. He made significant improvement as an inpatient over a period of three weeks and was discharged with a plan for community follow-up for physical and mental health needs. DISCUSSION: It is important that clinicians are aware of the serious adverse consequences of heavy N2O use so they can appropriately recognize neurological consequences of N2O use and also educate the public on its potentially hazardous effects.