Neurological Impairment in a Young Population Exposed to Recreational Nitrous Oxide (N2O)

A Retrospective Study of Neurological Impairment in a Young Population Exposed to Recreational Nitrous Oxide

Nitrous oxide (N2O) is a colorless, flammable, analgesic gas used in surgery and dentistry. The consumption of N2O has increased among young French people aiming to relax because of its short-lived neuropsychological effect (euphoria, depersonalization, analgesia) and its wide availability on the market.

It can be responsible in case of prolonged use and overdose of a vitamin B12 deficiency with possible neuropsychiatric complications: sensitivomotor neuropathy, myelopathy, behavioral and cognitive disorders of acute or sub-acute installation.

N2O inhibits the activitý of methionine synthase, decreases the activitý of methylmalonyl-CoA mutase leading to vitamin B12 deficiency but in addition to the interference with vitamin B12 metabolism there seems to be a direct toxicity of N20.

Myelin alteration was the typical electromyography finding but new axonal profiles were also described. Since myelopathy affects both the posterior and lateral cords, combined spinal cord sclerosis is the most common location of injury associated with N2O intoxication.

Study Overview

• Status: Terminated
• Conditions: Neuropathy
• Intervention / Treatment: Other: None, pure observationnal study

• Study Type: Observational
• Enrollment (Actual): 20

Contacts and Locations

Study Locations

• France
  • Nîmes, France, 30029
    • CHU de Nîmes

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 15 years and older (Child, Adult, Older Adult)
• Accepts Healthy Volunteers: No

• Sampling Method: Probability Sample

Study Population

patients presenting to the CHU of Nîmes with an acute or sub-acute neurological picture after having consumed N2O

Description

patients presenting to the CHU of Nîmes with an acute or sub-acute neurological picture after having consumed N2O

-

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Patients; patients presenting to the CHU of Nîmes for an acute or subacute neurological picture after having consumed N2O.	Other: None, pure observationnal study; None, pure observational study following the usual management of the patients

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
MRC score	MRCss - Medical Research Council sum score : This score assigns a rating to each muscle group: "0" = absence of visible contraction visible contractions, " 1 " = visible contractions without movement of limbs, " 2 " = insufficient 2" = insufficient movements to overcome weightlessness, "3" = movements to overcome weightlessness, "4" = movements against weightlessness and resistance, "5" = normal muscle strength.	baseline
Romberg score	A positive Romberg test means the presence of sensory ataxia	Baseline
INCAT Sensory Sum score (ISS)	grades from 0 (no involvement) to 20 (severe involvement)	Baseline
ONLS - Overall Neuropathy Limitations Scale	Overall Neuropathy Limitation Scale = arm scale (range 0 to 5) + leg scale (range 0 to 7); (range: 0 (no disability) to 12 (maximum disability)	Baseline
Rankin score	disability measurement score from 0 (none) to 6 (death)	Baseline
vitamin B12 level	vitamin B12 level in µmom/L	baseline
methyl malonic acid level	methyl-malonic acid level	baseline
electroneuromyogram	Normal Yes/No	baseline
Cerebral MRI	lesions yes/No	baseline
Pan-medullary MRI	lesions yes/No	baseline

Collaborators and Investigators

• Sponsor: Centre Hospitalier Universitaire de Nīmes
• Investigators: Study Director: Anissa MEGZARI, Centre Hospitalier Universitaire de Nîmes

Study record dates

Study Major Dates

• Study Start (Actual): August 22, 2022
• Primary Completion (Actual): May 3, 2025
• Study Completion (Actual): May 3, 2025

Study Registration Dates

• First Submitted: July 19, 2022
• First Submitted That Met QC Criteria: July 19, 2022
• First Posted (Actual): July 21, 2022

Study Record Updates

• Last Update Posted (Actual): June 1, 2026
• Last Update Submitted That Met QC Criteria: May 28, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Other Study ID Numbers: Local/2022/II-03

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No