Subacute combined degeneration induced by nitrous oxide inhalation: Two case reports

Multidisciplinary rehabilitation following recreational nitrous oxide (N2O) misuse: evaluating service provision and rehabilitation outcomes in a cohort with serious disability

Purpose: Recreational nitrous oxide (N2O) misuse is increasing globally. Chronic misuse can cause neurological impairments that require rehabilitation, though literature characterising rehabilitation is limited. This study aimed to evaluate rehabilitation service provision for impairments resulting from N2O misuse. Methods: A retrospective audit of hospitalised patients referred for rehabilitation for N2O toxicity was conducted between 2015 and 2022 at a single metropolitan hospital. Data were collected via medical record audit and analysed via descriptive and non-parametric statistics. Results: 16 eligible cases were identified, aged 18-43 years (50% female/male), with increasing case frequency. 12 cases received inpatient rehabilitation episodes for multifactorial sensorimotor, cognitive and psychosocial impairments. Cases articulated diverse rehabilitation goals and received intervention from a median of 6 clinical disciplines. All cases required assistance to mobilise or perform self-care activities on admission. Functional Independence Measure (FIM) scores significantly improved with rehabilitation (median FIM 84[75-93] to 117[112-123], p < .001). Despite gains in independence, all cases required referral for ongoing rehabilitation post-discharge. Conclusions: Demand for inpatient rehabilitation for disabling N2O toxicity appears to be increasing. In this series, cases were young, exhibited serious impairments, and had multidisciplinary rehabilitation needs. Inpatient rehabilitation led to significant functional improvements, though ongoing disability was evident post-discharge.

A Case of Fever, Impaired Consciousness, and Psychosis Caused by Nitrous Oxide Abuse and Misdiagnosed as Acute Meningitis

Nitrous oxide (N2O) is readily available, and its abuse for recreational purposes has become a social problem. In Japan, where N2O is strictly prohibited for non-medical use, abuse is often overlooked due to a lack of experience in the field. N2O abuse causes various long-term symptoms, including vitamin B12 deficiency, myelopathy, myeloneuropathy, subacute combined degeneration, mood changes, and psychosis. The diagnosis of N2O abuse is difficult due to the compound's short half-life and rapid elimination through the lungs. This report describes a case of fever and impaired consciousness in a patient with a history of N2O abuse.

Neuropsychiatric disorders associated with recreational nitrous oxide use

BACKGROUND

Recreational nitrous oxide use has grown in popularity among young people and has become a serious public health problem. Chronic use of nitrous oxide can lead to a functional vitamin B12 deficiency and neuropsychiatric complications.

PURPOSE

This study aimed to investigate the characteristics of neuropsychiatric complications associated with nitrous oxide use and to enhance clinicians' awareness of this public health problem.

METHODS

We retrospectively reviewed 16 patients with neuropsychiatric disorders related to nitrous oxide use who were treated in our hospital from June 2021 to October 2022. Their demographics, clinical features, investigations, treatments and outcomes were analyzed.

RESULTS

There were ten males and six females between the ages of 17 and 25 with a mean age of 20.5 ± 2.6 years. Thirteen patients sought medical help from the neurology clinic. Two patients presented to the psychiatric department and one patient presented to the emergency department with acute cognitive impairment. All 16 patients presented with neurological symptoms, such as paresthesia in four limbs or the lower limbs, unsteady gait and weakness. Twelve patients developed psychiatric symptoms, such as hallucinations, agitation, depression, emotional indifference and personality changes. Twelve patients had vitamin B12 deficiency. All 16 patients had hyperhomocysteinemia. Fourteen patients showed abnormal high signal on T2-weighted imaging and an inverted "V" sign in axial view, mainly involving the cervical cord. Neuropsychiatric symptoms improved with vitamin B12 treatment and cessation of nitrous oxide use in all cases.

CONCLUSION

Young adults are predominately involved in recreational use of nitrous oxide, which can cause neuropsychiatric complications. The clinical response to vitamin B12 supplementation and cessation of nitrous oxide use is generally good. Clinicians should recognize nitrous oxide use as a public health problem and a cause of a wide range of neuropsychiatric symptoms, particularly in younger patients.

Severe length-dependent peripheral polyneuropathy in a patient with subacute combined spinal cord degeneration secondary to recreational nitrous oxide abuse: A case report and literature review

Nitrous oxide abuse can have detrimental effects on the central and peripheral nervous systems. This case study report aims to demonstrate a combination of severe generalized sensorimotor polyneuropathy and cervical myelopathy related to vitamin B₁₂ deficiency following nitrous oxide abuse. We present a clinical case study and literature review examining primary research-published between 2012 and 2022-reporting nitrous oxide abuse affecting the spinal cord (myelopathy) and peripheral nerves (polyneuropathy); 35 articles were included in the review with a total of 96 patients, where the mean "patients" age was 23.9 years and were in a 2:1 male/female ratio. Of the 96 cases, within the review, 56% of patients were diagnosed with polyneuropathy, most commonly impacting the nerves of the lower limb (62%), while 70% of patients were diagnosed with myelopathy, most commonly impacting the cervical region (78%) on the spinal cord. In our clinical case study, a 28-year-old male underwent a multitude of diagnostic investigations for bilateral "foot drop" and sense of lower limb stiffness as ongoing complications of a vitamin B₁₂ deficiency secondary to recreational nitrous oxide abuse. Both the literature review and our case report emphasize the dangers of recreational nitrous oxide inhalation, colloquially termed "nanging" and the risks it presents to both the central and peripheral nervous systems, which is erroneously considered by many recreational drug users to be less harmful than other illicit substances.

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.

Serum copper decrease and cerebellar atrophy in patients with nitrous oxide-induced subacute combined degeneration: two cases report

Background

Subacute combined degeneration (SCD) is a neurological complication commonly associated with vitamin B₁₂ deficiency. It can result from nitrous oxide (N₂O) abuse and cause neuropsychiatric symptoms. However, there has been no literature regarding alterations of serum copper and cerebellum in SCD patients.

Case presentation

We reported two cases of young SCD patients with histories of N₂O abuse. In these cases, elevated homocysteine, macrocytic anemia, spinal cord abnormalities, and peripheral nerve injuries were detected. In addition, decreased serum copper level and cerebellar atrophy were reported for the first time. The patients’ symptoms improved after withdrawal of N₂O exposure and vitamin B₁₂ supplements.

Conclusion

We reported two SCD cases with serum copper alteration and cerebellar atrophy after N₂O abuse for the first time. These might be crucial complements to the diagnosis of SCD.

Key Characteristics of Nitrous Oxide-Induced Neurological Disorders and Differences Between Populations

Background: Nitrous oxide (N₂O), commonly known as laughing gas, is inhaled recreationally because it produces the feelings of euphoria and freedom from pain. The risk of neurological dysfunction secondary to N₂O abuse and its clinical diagnosis are, however, not yet sufficiently recognized, especially in China. Here, we have summarized the key clinical characteristics of N₂O-induced neurological disorders.

Materials and Methods: We recruited 20 patients with N₂O-induced neurological disorders and analyzed their clinical features, laboratory data, magnetic resonance imaging and electromyography. We also carried out a literature review and compared 99 previously reported patients with our case series to confirm our results. Subgroup analysis was performed to explore the difference in demographical and clinical characteristics of N₂O abuse between Asian and non-Asian patients.

Results: The most common initial symptoms of N₂O-induced neurological disorders were weakness and/or paresthesia. Most patients presented with myelopathy and/or peripheral neuropathy. The most commonly involved segment of the spinal cord was the cervical spinal cord, extending over 4–6 vertebral levels, but more than half of the patients with myelopathy had no sensory change at the corresponding spinal level. Homocysteine was found to be the most sensitive and practical indicator for diagnosis. Subgroup analysis showed that the Asian patients (median: 22.0 years old, Q1–Q3:19.0–26.0 years old) with N₂O abuse were younger than non-Asian patients [26.0 (22.3–31.0) years old, P = 2.8 × 10⁻⁴]. The incidence of myelopathy combined with peripheral neuropathy was significantly higher in Asian patients than in non-Asian patients, who had myelopathy or peripheral neuropathy (P = 2 × 10⁻⁵).

Conclusions: Key clinical characteristics of N₂O abuse are longitudinally extensive cervical myelopathy and peripheral neuropathy. Recognition of these traits in young people in the age group of 20–30 years will provide important guidance for accurate diagnosis of neurological disease associated with N₂O abuse. The clinical manifestations differ in Asian patients and non-Asian patients.