Neurological Impairment in a Young Population Exposed to Recreational Nitrous Oxide

Study Overview
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Brief Summary
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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.

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

Conditions
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Neuropathy

Intervention / Treatment
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* Other: None, pure observationnal study


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

Ages Eligible for Study
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Minimum Age: 15 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Patients<br>patients presenting to the CHU of Nîmes for an acute or subacute neurological picture after having consumed N2O. | Other: None, pure observationnal study<br>* None, pure observational study following the usual management of the patients<br>|

What is the study measuring?
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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 |