{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,25]],"date-time":"2026-09-25T13:01:59Z","timestamp":1790341319930,"version":"4.1.0"},"reference-count":29,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2026,9,25]],"date-time":"2026-09-25T00:00:00Z","timestamp":1790294400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["J. Clin. Med.","JCM"],"abstract":"<jats:p>Background\/Objectives: Nitrous oxide is known to cause neurological damage. We investigated the potential effects of nitrous oxide (N2O) abuse on the optic nerve through comprehensive ophthalmological evaluation of patients diagnosed with N2O-related neurological disorders. Methods: This retrospective, monocentric case series included patients hospitalized for N2O-related neurological manifestations in the neurology department of a French tertiary care center. Suspected optic neuropathy was defined as abnormal retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL) thickness according to age- and sex-adjusted normative values, in the presence or absence of visual field defects. Results: Ten patients (mean age: 22.2 \u00b1 3.6 years) were assessed. They all presented with symptoms typical of N2O-induced neuropathy or myelopathy and elevated blood methylmalonic acid and total homocysteine levels, which are markers of vitamin B12 inactivation. Three patients showed decreased RNFL and GCL thickness. The cumulative exposure to N2O was higher (3220 \u00b1 2801 kg vs. 165 \u00b1 158 kg) and the consumption duration was longer (36 \u00b1 32 vs. 8 \u00b1 8 months) in these three patients compared to those without optic nerve involvement. Conclusions: This preliminary case series suggests that massive and prolonged N2O exposure may be associated with subclinical optic neuropathy, possibly mediated by vitamin B12 inactivation. Given the growing prevalence of recreational N2O use, ophthalmological evaluation including OCT could be considered in patients with heavy or prolonged use and neurological symptoms. These findings are hypothesis-generating and require confirmation in larger prospective studies.<\/jats:p>","DOI":"10.3390\/jcm15197475","type":"journal-article","created":{"date-parts":[[2026,9,25]],"date-time":"2026-09-25T12:31:44Z","timestamp":1790339504000},"page":"7475","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Optic Neuropathy Associated with Recreational Abuse of Nitrous Oxide: A Retrospective Case Series"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0009-0008-3284-0684","authenticated-orcid":false,"given":"Joseph","family":"Albou","sequence":"first","affiliation":[{"name":"Ophthalmology Department, Avicenne Hospital, 125 rue de Stalingrad, 93000 Bobigny, France"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"}]},{"given":"Julien","family":"Fallouh","sequence":"additional","affiliation":[{"name":"Ophthalmology Department, Avicenne Hospital, 125 rue de Stalingrad, 93000 Bobigny, France"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"given":"Bertrand","family":"Degos","sequence":"additional","affiliation":[{"name":"Neurology Department, Avicenne Hospital, 93009 Bobigny, France"},{"name":"Sorbonne Paris Nord University, 93000 Bobigny, France"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"given":"Franck","family":"Fajnkuchen","sequence":"additional","affiliation":[{"name":"Ophthalmology Department, Avicenne Hospital, 125 rue de Stalingrad, 93000 Bobigny, France"},{"name":"Centre d\u2019Imagerie et de Laser, 75015 Paris, France"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"}]},{"given":"Sylvia","family":"Nghiem-Buffet","sequence":"additional","affiliation":[{"name":"Ophthalmology Department, Avicenne Hospital, 125 rue de Stalingrad, 93000 Bobigny, France"},{"name":"Centre d\u2019Imagerie et de Laser, 75015 Paris, France"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"visualization","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"}]},{"given":"Julie","family":"Mazoyer","sequence":"additional","affiliation":[{"name":"Neurology Department, Avicenne Hospital, 93009 Bobigny, France"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"supervision","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7918-7845","authenticated-orcid":false,"given":"Audrey","family":"Giocanti-Aur\u00e9gan","sequence":"additional","affiliation":[{"name":"Ophthalmology Department, Avicenne Hospital, 125 rue de Stalingrad, 93000 Bobigny, France"},{"name":"Sorbonne Paris Nord University, 93000 Bobigny, France"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5090-7845","authenticated-orcid":false,"given":"H\u00e9lo\u00efse","family":"Torres-Villaros","sequence":"additional","affiliation":[{"name":"Ophthalmology Department, Avicenne Hospital, 125 rue de Stalingrad, 93000 Bobigny, France"},{"name":"Sorbonne Paris Nord University, 93000 Bobigny, France"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"conceptualization","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,25]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"3340","DOI":"10.1007\/s00415-024-12264-w","article-title":"Marked increase in severe neurological disorders after nitrous oxide abuse: A retrospective study in the Greater Paris area","volume":"271","author":"Dawudi","year":"2024","journal-title":"J. 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