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

Abstract

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.

Nitrous‐oxide‐induced polyneuropathy and subacute combined degeneration of the spine: clinical and diagnostic characteristics in 70 patients, with focus on electrodiagnostic studies

“…For example, Yu et al reported 54% loss to follow-up in their cohort study of 110 patients [23]. On average the prognosis is found to be good with percentages of recovery varying between 67% and 95% [12,23,24]. In our study, a large proportion of patients (81%) improved completely or with mild residual symptoms.…”

“…It is uncertain whether the reported amount and duration of N 2 O use is correct and therefore no correlation could be made with the severity of symptoms and EDx changes. Unfortunately, it is well known that in the N 2 O‐abuse population there is a large proportion lost to follow‐up, also seen in our cohort (40%) [14, 23, 24]. Therefore, data about ongoing N 2 O abuse were insufficient.…”

“…Clinically, the majority of patients presented with sensory more than motor complaints, with legs more involved than arms and with walking difficulties [5,6,8,14,16,20,24,31]. Micturition problems were reported in 20%, in patients with both proven PNP and/or SCD.…”

“…Literature on N 2 O abuse primarily focuses on N 2 O-induced SCD. Recently more has been published about N 2 O-induced PNP consisting of primarily axonal PNP, combined axonal and demyelinating PNP and rarely a pure demyelinating PNP [5,6,12,[16][17][18][19][20][21][22][23][24][25].…”

Nitrous oxide-induced neurotoxicity: Clinical characteristics and impacts on overall neurological impairments

“…Due to a lack of supervision measures and a large population, the number of cases of N 2 O-related neurological disorders in China has increased rapidly since 2016 (6)(7)(8)(9)(10)(11)(12). Published studies have typically focused on symptom presentations, imaging characteristics, laboratory findings, and distinctions from other subacute combined degenerations (SCDs).…”