Nitrous oxide abuse: single centre experience of nitrous oxide induced myeloneuropathy.

BACKGROUND

Over the last 3 years, there has been increasing awareness of nitrous oxide-induced myeloneuropathy, particularly among younger patients.

METHODS

We conducted a prospective and retrospective case series of patients presenting with nitrous oxide-associated myeloneuropathy to Tallaght University Hospital, between October 2022 and July 2024. Data were gathered regarding clinical presentation, investigations, and management of patients.

RESULTS

Eighteen patients were identified (mean age 20 years, 78% male). The most common presenting symptom was paraesthesia (15/18) followed by limb weakness (13/18) and gait impairment (8/18). All patients reported heavy use of inhaled nitrous oxide, with a minority (3/18) also reporting prophylactic use of B12 supplementation. Levels of vitamin B12 were low (4/18) or low normal (7/18) in the majority of patients. Homocysteine was raised in almost all patients in whom it was measured (14/16). Of those cases (16/18) where MR imaging of the spinal cord was available, T2 hyperintensity was noted in the cervical cord in 8/16 cases, and this extended to involve the thoracic cord in five of those cases. Of those who had nerve conduction studies performed (13/18), motor-predominant axonal neuropathy was the most common pattern seen.

CONCLUSION

Nitrous oxide abuse, and its neurological complications, continue to represent a significant public health concern, with associated burden on neurological services.