Nitrous oxide-induced myeloneuropathy: a case series

Nitrous oxide-induced myeloneuropathy in a Thai adolescent: a case report

Nitrous oxide, an inhalational anaesthetic, is popular with adolescents worldwide as an accessible recreational drug which induces a euphoric effect. However, chronic abuse leads to serious complications such as myeloneuropathy and bone marrow suppression by inactivation of vitamin B12. A 17-year-old girl presented with nitrous oxide-induced myeloneuropathy. She reported chronic nitrous oxide inhalation for 10 months and was admitted to the emergency department on account of repeated falls for 2 weeks. She also had ascending paraesthesia in both legs and urinary incontinence. Neurological examination demonstrated bilateral lower extremity weakness [motor power: proximal muscles 4/5, plantar flexion and extensor hallucis longus (EHL) 3/5], decreased sensation, proprioception and vibration of the lower extremities. Deep tendon reflexes were absent in the ankles and knees. Laboratory results demonstrated mild anaemia [Hb 11.2 g/dL (12.0-16.0), haematocrit 35.4% (36-50), MCV 89.4 fl (78-102)] with significant hypersegmented neutrophils in a peripheral blood smear. Serum vitamin B12 was 340 pg/mL (197-771), but serum homocysteine was increased at 65.8 µmol/L (5-15). A nerve conduction study was prolonged, and F-waves were absent from the bilateral perineal and tibial nerves, indicating diffuse demyelinating motor polyneuropathy. Magnetic resonance imaging of the whole spine demonstrated faint T2 hypersignal intensity and an inverted V-shape appearance at the posterior column of the upper thoracic cord (around T2-T6), a pathognomonic sign of vitamin B12 deficiency or subacute combined degeneration of the nitrous oxide-induced myeloneuropathy. A 7-day course of 1000 µg cyanocobalamin was given intramuscularly, followed by weekly doses for 4 weeks. Supplements of daily oral vitamin B1, B6 and B12 (65 µg vitamin B12) were administered, along with rehabilitation. At the 6-months outpatient follow-up, there were a few residual neurological abnormalities: weakness of the left EHL (grade 4/5) and an absent deep tendon reflex in the left ankle. This case emphasises the significant health consequences of chronic abuse of nitrous oxide, myeloneuropathy and megaloblastic anaemia, by inactivation of vitamin B12. The myelopathy is noticeably improved by cyanocobalamin.Abbreviations: EHL: extensor hallucis longus; MRI: magnetic resonance imaging; NCS: nerve conduction study.

[Nitrous oxide as a party drug]

In recent years, reports of health problems associated with nitrous oxide consumption have significantly increased. In Germany, nitrous oxide (N2O) is easily available in cartridges without legal restrictions. The main reason for its popularity in the party scene are the euphoric, psychedelic effects of the gas. In addition to severe and sometimes irreversible health problems associated with long-term use of nitrous oxide, e.g., anemia and nerve damage, life-threatening or fatal consequences of acute nitrous oxide consumption can also occur: accidents under the influence of nitrous oxide, pneumothorax, pneumopericardium and shock due to an explosive increase in airway pressure when inhaled directly from the cartridge. But the most common cause of severe complications is asphyxia as the gas is usually inhaled pure from large balloons and without oxygen. The resulting hypoxia during use may be perpetuated by the diffusion hypoxia that occurs during the reoxygenation period. Nitrous oxide as a cause in accidental or intoxication events is usually not detectable but can only be identified as a trigger based on the patient's history or the circumstances. Acute medical treatment is symptomatic.

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.

Evaluation of an ambulatory care pathway for patients with nitrous oxide-induced myeloneuropathy

Introduction

Cases of nitrous oxide (N2O)-induced myeloneuropathy are increasing at UK hospitals. At our centre, a dedicated ambulatory care pathway, endorsed nationally, was established to treat and monitor patients with N2O-myeloneuropathy in 2021 and refined through three audit cycles. We analysed the outcomes of patients on this pathway to better understand factors associated with non-engagement. Alongside, a novel approach using WhatsApp for questionnaire delivery was trialled in an attempt to improve engagement with treatment.

Methods

Patients on the N2O ambulatory care pathway were identified from MDT meeting lists from 9 September 2022 to 25 April 2023. Clinical data were collected via electronic clinical records, including the most recent neurological examination and reason for discharge from the pathway. Patients identified from MDT lists from 27 January 2023 to 14 March 2023 were approached to participate in weekly 12-item surveys, delivered via WhatsApp. This was approved as a service development project with approval for WhatsApp use given by the chief clinical information officer.

Results

35/56 (62.5%) patients were discharged from ambulatory care due to non-attendance and 17/56 (30.4%) completed their treatment course. The median time from initial presentation to discharge was 49 days. 24/40 (60.0%) of patients with a final neurological examination documented had a residual deficit, with objective sensory deficits most common. 12 patients were approached to receive weekly questionnaires via WhatsApp. 5/8 who expressed interest returned a consent form. All participants were withdrawn due to non-response or participant choice. 1/5 returned more than two surveys.

Conclusion

Despite poor participation in surveys delivered via WhatsApp, novel approaches are needed to improve engagement with patients on the N2O ambulatory care pathway.

Nitrous Oxide as an Emerging Cause of Subacute Combined Degeneration and Polyneuropathy: A Two-Case Report

Recreational use of nitrous oxide (N2O), commonly known as laughing gas, has increased in the last few years, bringing an increase in the number of reported cases of toxicity due to this gas. Subacute combined degeneration (SCD) of the spinal cord is the most frequently reported neurological disorder due to the use of N2O, as well as polyneuropathy and even psychiatric symptoms. All of these disorders are consequences of a functional deficit of vitamin B12. We are reporting the cases of two patients with a history of N2O abusive use presenting to the emergency department with progressive symptoms of paresthesia, ascending symmetric paraparesis, and gait ataxia, emulating the clinical characteristics of Guillain-Barré Syndrome (GBS). In both cases, magnetic resonance imaging (MRI) showed findings compatible with transverse myelitis of the cervical spinal cord, and electrodiagnosis studies reported the presence of polyneuropathy with a mixed mechanism. All these findings together pointed to the presence of myeloneuropathy due to a vitamin B12 deficit induced by the prolonged use of N2O. Symptoms improved gradually with vitamin B12 supplementation and abstinence from N2O. It is important to acknowledge the clinical characteristics of complications due to neurotoxicity induced by N2O. Such complications are potentially reversible if they are treated appropriately and quickly. Considering the increase in N2O abuse, it should be considered a probable cause when treating patients with myelopathy and/or neuropathy of an unusual etiology.

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.

Recreational nitrous oxide and thrombotic events: a case series

Background

The study aimed to elucidate the prevalence of nitrous oxide (N2O) usage in patients with unexplained venous thromboembolism (VTE), highlighting the potential association with hyperhomocysteinaemia (HHcy).

Methods

We conducted a retrospective study at the Royal London Hospital, examining cases of N2O-related VTE from March to August 2023. Among 50 patients identified, four (8%) had recent unprovoked VTE. Patient data were collected based on N2O ambulatory emergency care pathway admissions.

Results

Among the 50 patients identified, four (8%) had recent or concurrent VTE. Three were male (75%), with an ethnic distribution of 50% Asian or Asian British and 50% Black or Black British. Patients were distributed across quintiles of the index of multiple deprivation. All had actual or functional vitamin B12 deficiency.

Discussion

The association between N2O use and VTE requires further investigation, though a plausible mechanism involving HHcy has been proposed. Clinicians should be vigilant for VTE in N2O users, especially those presenting with unexplained symptoms. VTE prophylaxis may be worth considering, particularly if continued exposure to nitrous oxide is anticipated.

Conclusion

N2O misuse may increase the risk of VTE, warranting attention from healthcare providers. Further research is needed to elucidate this association and inform preventive strategies. Public awareness about the risks of N2O remains essential.

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.

Nitrous oxide abuse direct measurement for diagnosis and follow-up: update on kinetics and impact on metabolic pathways

Recreational use of nitrous oxide (N2O) has become a major health issue worldwide, with a high number of clinical events, especially in neurology and cardiology. It is essential to be able to detect and monitor N2O abuse to provide effective care and follow-up to these patients. Current recommendations for detecting N2O in cases of recreational misuse and consumption markers are lacking. We aimed to update current knowledge through a review of the literature on N2O measurement and kinetics. We reviewed the outcomes of experiments, whether in preclinical models (in vitro or in vivo), or in humans, with the aim to identify biomarkers of intoxication as well as biomarkers of clinical severity, for laboratory use. Because N2O is eliminated 5 min after inhalation, measuring it in exhaled air is of no value. Many studies have found that urine and blood matrices concentrations are connected to ambient concentrations, but there is no similar data for direct exposure. There have been no studies on N2O measurement in direct consumers. Currently, patients actively abusing N2O are monitored using effect biomarkers (biomarkers related to the effects of N2O on metabolism), such as vitamin B12, homocysteine and methylmalonic acid.

A recent surge of nitrous oxide misuse around London which merits a public health warning

BACKGROUND

Use of nitrous oxide (N2O) gas for recreational purposes by young people is increasingly recognized as a public health hazard in the UK.

METHODS

We looked at the hospital records of patients admitted over the last 4 years to a single neurological centre in Essex to determine the demographics, presentation, and management of patients presenting with symptoms of N2O toxicity from its recreational use.

RESULTS

Of the 17 patients (mean age = 22.9 ± 3 years) admitted between September 2018 and October 2022, 70% were admitted between January and October 2022. All patients reported limb paraesthesiae and 16/17 reported (95%) imbalance; 11/17 (65%) showed objective limb weakness. Serum B12 concentration was low in 9/17 (53%). Plasma methylmalonic acid (n = 7) and homocysteine (n = 8) levels were elevated in all patients tested. Spinal cord Magnetic Resonance Imaging (MRI) imaging was abnormal in 10/17 (59%) patients. Nerve conduction studies were abnormal in 10/13 (77%) patients, with evidence of a symmetric, length-dependent, large fibre neuropathy.

CONCLUSIONS

There has been a recent surge of cases with neurological complications of recreational N2O abuse in the UK, with a relatively greater rate in 2022. Greater awareness of this condition amongst clinicians and health regulators is urgently required to prevent harm from N2O misuse in young people.

Vision Threatening Raised Intracranial Pressure Associated with Recreational Nitrous Oxide Use

Nitrous oxide is used as an anaesthetic and analgesic agent in the medical setting and is known to cause raised intracranial pressure. The use of nitrous oxide recreationally for the drug's euphoric and relaxant properties has been linked to multiple neurological and psychiatric sequelae including neuropathy, myelopathy, and psychosis. We describe a case of a young person who declared heavy nitrous oxide use resulting in vision-threatening papilloedema secondary to raised intracranial pressure. He underwent emergency lumbar drainage alongside high-dose acetazolamide and parenteral vitamin B12 injections. To our knowledge, there have yet to be other reports of cases where heavy nitrous oxide use has caused secondary pseudotumor cerebri syndrome.