Diagnosis and management of toxicity associated with the recreational use of nitrous oxide

Neurological disorders caused by recreational use of nitrous oxide-a retrospective study from a German metropolitan area and review of the literature

BACKGROUND

The recreational use of nitrous oxide (N2O) has seen a worldwide rise in the recent years, resulting in an increased incidence of neurological complications due to N2O-induced functional vitamin B12 deficiency. Here, we report on a cohort of patients admitted to a tertiary care center with neurological symptoms in the context of recreational N2O use between 2020 and 2024.

METHODS

We screened the database of the University Hospital Frankfurt for patients ≥ 18 years of age who presented with neurological deficits and a history of N2O consumption between January 2020 and December 2024. We analyzed the spectrum of neurological deficits as well as radiological and laboratory findings.

RESULTS

We identified a total of 20 patients, 16 males and 4 females, with a median age of 21 years. We found a steady increase in the number of cases, with no cases in 2020 and 2021 and a definite peak in 2024. The mean daily N2O consumption was 2500 g. All patients reported sensory deficits; 85% had gait disturbances and 70% had motor deficits. Less frequent symptoms included pain, bladder or bowel dysfunction, fatigue and spasticity. The median score on the modified Rankin scale (mRS) was 2, with some patients being wheelchair-bound. The most frequently observed lesion pattern was combined myelo-polyneuropathy. T2-hyperintense myelon lesions were observed in 11 of 15 patients (73.3%). Surprisingly, laboratory work-up revealed normal vitamin B12 levels in nearly all patients (95%), whereas homocysteine and methylmalonic acid levels were prominently elevated in all patients (100%). In addition, 13 patients (65%) presented with hematological abnormalities. All of the patients who presented for follow-up (20%) reported continued use of N2O. There was no neurological improvement in any of these cases.

CONCLUSIONS

Our study confirms that the increasing incidence of N2O-induced neurotoxicity reported in other countries can also be observed in Germany. Therefore, it underlines the relevance of the current debate on health policies. In addition, our study highlights the pitfalls of vitamin B12 laboratory testing and emphasizes the need to address substance addiction in treatment.

Mechanisms and recent advances in the diagnosis and treatment of nitrous oxide-induced peripheral neuropathy: a narrative review

Under standard conditions, nitrous oxide (N2O) manifests as a colorless, odorless gas with a mildly sweet taste. The compound finds applications in various fields, including its use as an aerosol propellants, an accelerant in motor racing, and an anesthetic in surgical procedures and dentistry. Unfortunately, the recreational misuse of N2O has become prevalent among young individuals due to its euphoric and hallucinogenic effects. Compounding this issue is the fact that nitrous oxide can be easily obtained from over-the-counter household items, facilitating its non-medical use. The global community has witnessed a surge in the recreational utilization of nitrous oxide gas in recent years. Despite the widespread non-medical abuse of N2O, there remains inadequate understanding of the potential adverse effects resulting from exposure to it. This paper provides an overview of management findings, laboratory and electrodiagnostic characteristics, as well as clinical presentations associated with neurological disorders induced by nitrous oxide usage.

The boon and bane of nitrous oxide

Nitrous oxide (N2O) has been known since the end of the eighteenth century. Today, N2O plays a huge role as a greenhouse gas and an ozone-depleting stratospheric molecule. The main sources of anthropogenic N2O emissions are agriculture, fuel combustion, wastewater treatment, and various industrial processes. By contrast, the contribution of medical N2O to the greenhouse effect appears to be small. The recreational and medical uses of N2O gradually diverged over time. N2O has analgesic and anesthetic effects, making it widely used in modern dentistry and surgery. New research has also begun studying N2O's antidepressant actions. N-methyl-D-aspartate (NMDA) antagonism and opioid effects are believed to be the main underlying biochemical mechanisms. At this point, numerous questions remain open and, in particular, the conduct of larger clinical trials will be essential to confirm N2O's use as a rapid-acting antidepressant. The N2O concentration delivered, the duration of a single inhalation, as well as the number of inhalations ultimately required, deserve to be better understood. Finally, the non-medical use of N2O has gained significant attention in recent years. Sudden deaths directly attributed to N2O are primarily due to asphyxia. Heavy, chronic N2O use may result in vitamin B12 deficiency, which, among other things, may cause megaloblastic anemia, venous thrombosis, myeloneuropathy, and skin pigmentation. Helpful biochemical tests include homocysteine and methylmalonic acid. The centerpiece of treatment is complete cessation of N2O use together with parenteral administration of vitamin B12.

Neuropathy with Cerebral Features Induced by Nitrous Oxide Abuse-A Case Report

Nitrous oxide abuse may cause functional cobalamin deficiency and subsequent damage to the peripheral nerves, the spinal cord, and the brain, a symptom complex best described by the term cobalamin neuropathy. Here, we report a case of cobalamin neuropathy with uncommon cerebral symptomatology following nitrous oxide intoxication and contextualize the symptomatology. A 22-year-old male with a history of mixed drug dependency presented at the emergency room after inhaling six 615 g cylinders, equal to ~1800 L, of nitrous oxide daily for two weeks. His main complaints were rapidly progressing paresthesias and gait difficulties, but he was also found to suffer from memory impairment and signs of extrapyramidal pathology in the form of dystonic posturing and athetosis. Neuroimaging demonstrated spinal cord hyperintensities consistent with subacute combined degeneration. The patient had low serum cobalamin and high plasma homocysteine, suggesting cobalamin neuropathy. After commencing treatment with parenteral hydroxocobalamin, plasma homocysteine normalized. The extrapyramidal symptoms disappeared during the first days of treatment, whereas the cognitive and peripheral symptoms only partially resolved over the following 20 days. This case highlights how neurological symptoms such as hyperkinetic movements and memory impairment may be associated with chronic nitrous oxide abuse. It is unclear to what extent these and other symptoms of cobalamin neuropathy are reversible, which underscores the public health concern.