Marked increase in severe neurological disorders after nitrous oxide abuse: a retrospective study in the Greater Paris area

BACKGROUND

Recreational nitrous oxide (N2O) use has become more widespread worldwide, leading to an increase in myelopathies and peripheral neuropathies. The aim of this study was to describe clinical and socioeconomical characteristics of severe N2O-induced (NI) neurological disorders (NI-NDs), to determine its incidence in the Greater Paris area and to compare it with that of similar inflammatory neurological disorders.

METHODS

We performed a retrospective multicentric cohort study of all adult patients with severe NI-NDs in the neurology and general internal medicine departments of the Greater Paris area from 2018 to 2021. The incidence was compared with that of non-NI-myelitis and Guillain-Barré syndrome (GBS) using a sample of 91,000 hospitalized patients sourced from health insurance data.

RESULTS

Among 181 patients, 25% had myelopathy, 37% had peripheral neuropathy and 38% had mixed disease. Most were aged between 20 and 25 years, lived in socially disadvantaged urban areas, and exhibited high rates of unemployment (37%). The incidence of NI-NDs increased during 2020 and reached a peak mid-2021. The 2021 incidence in 20-25-year-olds was 6.15 [4.72; 8.24] per 100,000 persons for NI-myelopathy and 7.48 [5.59; 9.37] for NI-peripheral neuropathy. This was significantly higher than for non-NI-myelitis (0.35 [0.02; 2.00]) and GBS (2.47 [0.64; 4.30]). The incidence of NI-NDs was two to three times higher in the most socially disadvantaged areas.

CONCLUSION

The recent increase in recreational N2O use has led to a rise in the incidence of severe NI-NDs, particularly in young adults with low socioeconomic status for whom NI-NDs strongly outweigh similar neurological disorders.

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.

Does nitrous oxide addiction exist? An evaluation of the evidence for the presence and prevalence of substance use disorder symptoms in recreational nitrous oxide users

BACKGROUND

Prevalence of nitrous oxide (N2 O) use appears to be increasing in numerous countries worldwide, and excessive use has been associated with physical and mental problems. Because there currently is no consensus whether N2 O has addictive potential, we aimed to evaluate the evidence for the presence and prevalence of DSM-5 substance use disorder (SUD) symptoms in N2 O users.

ANALYSIS

A literature search was conducted to assess the evidence for the presence of any of the 11 DSM-5 SUD symptoms in N2 O users and the prevalence experiencing those symptoms. A substantial part of the studied N2 O users use more than intended (i.e. 46% to 98%) and spend a substantial amount of time using N2 O. At least some of the studied N2 O users experience interpersonal problems (i.e. 13% to 80%) and use N2 O in risky situations, such as driving under the influence. Evidence for the other criteria is either insufficient or inconclusive.

CONCLUSIONS

The literature base for the presence and prevalence of DSM-5 substance use disorder (SUD) symptoms in nitrous oxide (N2 O) users is limited and largely consists of qualitative studies and case studies, but it provides consistent evidence for the presence of at least four SUD criteria in heavy N2 O users. N2 O could well be addictive and should be treated as a potentially addictive substance until systematic assessments can provide evidence-based guidance to users, healthcare professionals and legislators.

Factors affecting the topography of nitrous oxide-induced neurological complications

BACKGROUND

The factors underlying the topography of nitrous oxide (N2O)-induced neurological complications are unknown.

METHODS

We included all consecutive patients admitted to the university hospital of Marseille for N2O-induced neurological complications in a prospective observational study. Patients underwent neurological examination, spinal cord magnetic resonance imaging, and nerve conduction studies within the first 4 weeks after admission.

RESULTS

In total, 61 patients were included: 45% with myeloneuropathy, 34% with isolated myelopathy, and 21% with isolated neuropathy. On multivariable analysis, the odds of myelopathy were associated with the amount of weekly N2O consumption (~600 g cylinder per week, odds ratio [OR] = 1.11, 95% confidence interval [CI] = 1.001-1.24). The extent of the myelopathy (number of vertebral segments) was correlated with the number of ~600-g cylinders consumed weekly (ρ = 0.40, p < 0.005). The odds of neuropathy were associated with the duration of consumption (per month; OR = 1.29, 95% CI = 1.05-1.58). Mean lower-limb motor nerve amplitude was correlated with the duration of consumption (in months; ρ = -0.34, p < 0.05).

CONCLUSIONS

The odds of myelopathy increased with the amount of N2O consumption, and the odds of neuropathy increased with the duration of N2O exposure, which suggests distinct pathophysiological mechanisms underlying these two neurological complications.

Has there been an increase in nitrous oxide use and associated harms in Australia? An analysis of triangulated data sources, 2003-2020

BACKGROUND

There is growing concern, globally, regarding use of nitrous oxide (N2O) for intoxication purposes. This paper aims to examine trends in: (i) past six month N2O use among a sample of people who use regularly use ecstasy and/or other illicit stimulants (2003-2020); (ii) volume of N2O-related Google searches and social media posts (2009-2020); and (iii) N2O-related calls to Poisons Information Centres (PIC) (2004-2020).

METHODS

Data were obtained from annual interviews with sentinel samples of Australians aged ≥16 years who used ecstasy and/or other illicit stimulants ≥monthly and resided in a capital city (∼800 each year); Google search activity; social media posts; and exposure calls to four PIC.

RESULTS

Among samples of people who regularly use ecstasy and/or other illicit stimulants, past six-month N2O use increased 10% each year from 2009 to 2020, with the sharpest increase observed between 2015 and 2018 (25.4% p/year; 95% CI: 14.6-37.1). Frequency and quantity of N2O use remained stable and low. Google search probabilities increased by 1.8% each month from January 2009 and December 2019 (95% CI: 1.5-2.2), with the sharpest increase observed between July 2016 to December 2017 (6.0% p/month; 95% CI: 4.4-7.5). Social media posts increased 2.0% per month from January 2009 and December 2019 (95% CI: 1.1-3.0), with the sharpest increase observed between March and October 2017 (19.2% p/month; 95% CI: 1.7-39.7). The number of N2O-related calls to Australian PIC increased sixfold between 2016 (16) and 2020 (111).

CONCLUSIONS

Triangulation of various data sources indicate significant shifts in N2O use and harms in Australia. This includes increases in use, Google searches and social media posts, although these have plateaued in recent years, coupled with increased rates of harm. These findings correspond with evidence of a global increase in N2O use and harm, highlighting the need for education of both people who use N2O and health professionals.

Mechanisms Involved in the Neurotoxicity and Abuse Liability of Nitrous Oxide: A Narrative Review

The recreational use of nitrous oxide (N₂O) has increased over the years. At the same time, more N₂O intoxications are presented to hospitals. The incidental use of N₂O is relatively harmless, but heavy, frequent and chronic use comes with considerable health risks. Most importantly, N₂O can inactivate the co-factor cobalamin, which, in turn, leads to paresthesia's, partial paralysis and generalized demyelinating polyneuropathy. In some patients, these disorders are irreversible. Several metabolic cascades have been identified by which N₂O can cause harmful effects. Because these effects mostly occur after prolonged use, it raises the question of whether N₂O has addictive properties, explaining its prolonged and frequent use at high dose. Several lines of evidence for N₂O's dependence liability can be found in the literature, but the underlying mechanism of action remains controversial. N₂O interacts with the opioid system, but N₂O also acts as an N-methyl-D-aspartate (NMDA) receptor antagonist, by which it can cause dopamine disinhibition. In this narrative review, we provide a detailed description of animal and human evidence for N₂O-induced abuse/dependence and for N₂O-induced neurotoxicity.

Increasing recreational nitrous oxide use: Should we worry? A narrative review

BACKGROUND

Since 2000, the prevalence of recreational nitrous oxide (N₂O) use has increased in the Western world. Although N₂O is a relatively safe drug, the overall increase in the use of N₂O has concomitantly also initiated a modest but important increase in the number of young excessive users. The recent introduction of large 2 kg N₂O tanks, allowing high and prolonged dosing, has facilitated this excessive use. This is of concern, because repeated exposure to high doses of N₂O for a prolonged time is known to induce neurological damage, such as (irreversible) neuropathy and paralysis due to N₂O-induced vitamin B₁₂ deficiency. The increasing trend of recreational users with N₂O-induced neurological damage at emergency departments confirms the urgency of this development.

OBJECTIVE/METHODS

This narrative review describes recent trends in N₂O use and misuse, the adverse health effects associated with excessive use and the risk factors of excessive use.

RESULTS

Considering the rising trend in N₂O use, particularly among young and other vulnerable people, we propose to take legislative action to limit the availability of N₂O, and also advocate for better and timely education of non-users, users and medical professionals about the serious side-effects associated with excessive N₂O use.

CONCLUSION

It is concluded that the increase in excessive N₂O use is of serious concern.

Review article: Clinical manifestations and outcomes of chronic nitrous oxide misuse: A systematic review

Recreational nitrous oxide (N₂ O) use is widespread, and complications associated with its use are increasingly common. We sought to identify risk factors, clinical features and outcomes in individuals presenting with effects of chronic N₂ O abuse to develop an approach to clinical assessment and management. A systemic literature review was completed with searches conducted across EMBASE, MEDLINE, PSYCINFO and Cochrane databases. Our search strategy identified 612 studies, 105 met inclusion criteria, and 10 were added via hand search. Subjects from 24 case series and 91 case reports were typically in their 20s, using over 100 bulbs daily for several months. Neurological presentations, including sensory change, gait disturbance or weakness, were characteristic. Serum Vitamin B12 was normal or raised in 133 out of 243 case series subjects and 37 out of 84 reports. Serum homocysteine and methylmalonic acid were usually raised. Macrocytosis and anaemia were not commonly seen. MRI findings were abnormal with dorsal column change where specified, typically involving the cervical spine. Nerve conduction studies mostly reported a sensorimotor polyneuropathy. B12 replacement was the treatment of choice and partial recovery was most reported. This review highlights the dose-dependent nature of chronic N₂ O toxicity and recognises functional B12 deficiency as the cause. As B12 is often normal, homocysteine and methylmalonic acid are important biomarkers of disease. An approach to diagnosis is offered but requires validation in prospective studies. Research exploring B12 and methionine therapy is required to refine management.

Myeloneuropathy induced by recreational nitrous oxide use with variable exposure levels

BACKGROUND

Although several case series have described nitrous oxide-associated neurological disorders, a comprehensive assessment of exposure characteristics (e.g., time to onset, level of exposure) in substance abusers has not been performed. The aim of this study was to describe the onset patterns of recreational use of nitrous oxide-induced neurological disorders.

METHODS

All cases of neurological disorders related to nitrous oxide recreational use reported to the Hauts-de-France addictovigilance center between January 2019 and August 2020 were selected. Only cases requiring hospitalization with informative data to perform the nitrous oxide causality assessment were included.

RESULTS

A total of 20 cases from 5 hospitals were included. The male-to-female ratio was 6:1 and the median age was 19 years (range 16-34). The neurological presentation [myeloneuropathy 64% (7/11), sensorimotor neuropathy 36% (4/11)] included for all patients gait disorders due to proprioceptive ataxia and limb hypoesthesia. The median dose used per occasion was 100 cartridges (range 5-960; n=19). The median time from the start of nitrous oxide use to the onset of neurological symptoms was 6 months (range 0.7-54; n=16). The cumulative dose was significantly higher in patients with damage to all four limbs than in patients with lower limbs symptoms only (p=0.042).

CONCLUSIONS

A low intermittent exposure may be sufficient to cause neurological damage in some subjects, suggesting that, at the population level, there is no safe exposure to nitrous oxide in recreational settings. The severity of neurological impairment could increase once used at high doses and for prolonged durations of nitrous oxide.

The Clinical Presentations of Nitrous Oxide Users in an Emergency Department

Today, the concomitant abuse of nitrous oxide (N₂O) and illicit drugs is evident and problematic. However, there are few reports regarding the clinical manifestations of N₂O users when they present to the emergency department (ED). The purpose of this study was to describe the clinical presentations, the associated illicit substances used in combination, and the outcomes in N₂O users visiting the ED. This was a retrospective observational cohort study. All N₂O adult users admitted to the ED at Linkou Chang Gung Memorial Hospital between 2012 and 2020 were included. Demographic variables, clinical symptoms, and examination results were collected from medical records. Univariate comparisons were conducted between pure N₂O users and combined illicit drug users. A total of 40 patients were included, 24 of which were pure N₂O users. Limb weakness and numbness accounted for the majority of chief complaints. Neurologic symptoms were the most common clinical manifestations (90%). A more severe ED triage level, faster heart rate, greater agitation, and cardiovascular symptoms were significantly noted in combined illicit drug users. In ED, limb numbness/weakness should arouse physicians’ awareness of patients using N₂O. Combined use of N₂O and illicit drugs can cause great harm to health.

[Acute and chronic toxicities associated with the use and misuse of nitrous oxide: An update]

Nitrous oxide (N₂O) is used since the eighteenth century as an anesthetic and analgesic but also for recreational use. If the labelled uses of N₂O and their modalities are nowadays perfectly framed, the misuse of N₂O takes very alarming proportions among teenagers and young adults. This misuse is the cause of acute (hypoxia, barotrauma, burns, neuropsychiatric disorders) and chronic complications if repeated (myeloneuropathy, anemia, thrombosis, inhalant use disorder). The main mechanism of the latter is mainly related to a functional deficit in vitamin B12 induced by N₂O. The management of acute complications is symptomatic. The management of chronic complications is based on vitamin B12 supplementation. The best biomarker of chronic N₂O exposure is the elevation of the plasmatic level of methylmalonic acid. In all cases of recreational misuses, addiction treatment is necessary to prevent complications or their worsening by providing information in order to stop consumption.

Nitrous oxide-related neurological disorders: Clinical, laboratory, neuroimaging, and electrophysiological findings

BACKGROUND

Recreational N₂ O abuse is an important etiology of neurological impairment in young patients, which may easily be ignored clinically. Few current studies have investigated the characteristics or the effects experienced by its users. We aimed to explore any correlation between the clinical severity and biomarkers and spinal magnetic resonance imaging (MRI) abnormalities, identify independent factors associated with spinal MRI abnormalities, and ascertain factors affecting depression/anxiety in patients with N₂ O-related neurological disorders.

METHODS

Patients with N₂ O-related neurological disorders were enrolled retrospectively between February 2017 and July 2020. Their demographic, clinical, laboratory, neuroimaging, electrophysiological, and neuropsychological findings were analyzed. Correlation analyses were conducted using Spearman's or Pearson's correlation and linear regression analysis. Independent factors associated with spinal MRI abnormalities were identified using univariate and multivariate analyses.

RESULTS

The principal clinical manifestations of N₂ O-related neurological disorders (n = 63; 38 men, 25 women; mean age ± SD: 22.60 ± 4.46 years) were sensory disturbance, followed by gait disturbance and pyramidal tract damage. A significant negative correlation existed between serum vitamin B₁₂ levels and clinical severity (r = -0.309, p = .014), which disappeared after linear regression. An interval of less than 6 months between initial N₂ O abuse and hospitalization was independently associated with spinal MRI abnormalities (39.47% vs. 72.00%, respectively; χ²  = 6.40, p = .01). Thirty-eight (60.32%) and 40 (63.49%) patients experienced anxiety and depression, respectively. Moreover, the higher the clinical scores/serum homocysteine levels, the greater the severity of anxiety/depression (r = 0.442, p < .01; r = 0.346, p < .01; r = 0.477, p < .01; r = 0.324, p < .01).

CONCLUSIONS

The significant inverse correlation between initial vitamin B₁₂ levels and clinical severity could aid prognosis prediction in patients with N₂ O-related neurological disorders. Spinal MRI abnormalities were not related to clinical severity but depended on the time interval between initial N₂ O abuse and hospitalization. Anxiety and depression were common comorbidity in these patients, and their severity increased with the intensity of clinical impairment and/or serum homocysteine levels.

Nitrous Oxide-Induced Neurological Disorders - an increasing public health concern

BACKGROUND

Neurologic presentations resulting from nitrous oxide (N₂ O) abuse are increasing in Australia and worldwide. Despite known neuropsychiatric sequelae nitrous oxide canisters remain readily available and its use unregulated.

AIMS

To examine the demographics, clinical and electrophysiological findings of patients presenting with neurological complications of N₂ O 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 N₂ O 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 B₁₂ . Spinal magnetic resonance imaging was consistent with subacute combined degeneration (SACD) in 8. Nerve conduction studies revealed a motor or sensorimotor axonal neuropathy (3 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 N₂ O 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 B₁₂ replacement. Public health measures are required to limit the availability of N₂ O and to educate adolescents and young adults about the potential for significant harm. This article is protected by copyright. All rights reserved.

Nitrous oxide-induced myeloneuropathy

BACKGROUND AND PURPOSE

Nitrous oxide misuse is a recognized issue worldwide. Prolonged misuse inactivates vitamin B12, causing a myeloneuropathy.

METHODS

Twenty patients presenting between 2016 and 2020 to tertiary hospitals in Sydney with myeloneuropathy due to nitrous oxide misuse were reviewed.

RESULTS

The average age was 24 years, and mean canister consumption was 148 per day for 9 months. At presentation, paresthesias and gait unsteadiness were common, and seven patients were bedbound. Mean serum B12 was normal (258 pmol/L, normal range [NR] = 140-750) as was active B12 (87 pmol/L, normal > 35). In contrast, mean serum homocysteine was high (51 μmol/L, NR = 5-15). Spinal magnetic resonance imaging (MRI) showed characteristic dorsal column T2 hyperintensities in all 20 patients. Nerve conduction studies showed a predominantly axonal sensorimotor neuropathy (n = 5). Patients were treated with intramuscular vitamin B12, with variable functional recovery. Three of the seven patients who were bedbound at presentation were able to walk again with an aid at discharge. Of eight patients with follow-up data, most had persistent paresthesias and/or sensory ataxia. Mobility scores at admission and discharge were not significantly correlated with the serum total and active B12 levels or cumulative nitrous oxide use. There were no significant trends between serum active B12 level and cumulative nitrous oxide use (Spearman rho = -0.331, p = 0.195).

CONCLUSIONS

Nitrous oxide misuse can cause a severe but potentially reversible subacute myeloneuropathy. Serum and active B12 can be normal, while elevated homocysteine and dorsal column high T2 signal on MRI strongly suggest the diagnosis. Neurological deficits can improve with abstinence and B12 supplementation, even in the most severely affected patients.