Neurological complications and pathogenetic therapy for chronic nitrous oxide intoxication (“laughing gas”) in nightclub visitors

Abstract

Background. Nitrous oxide abuse (“laughing gas”, N2O) is common among young people attending nightclubs. Contrary to popular belief about the safety of N2O, in some cases neurological complications develop due to a deficiency of vitamin B12, the activity of which is blocked by N2O. Purpose of the study – to determine the typology and course of neurological disorders in a group of patients who regularly use “laughing gas”. To note the key diagnostic markers that allow verification of vitamin B12 deficiency induced by nitrous oxide consumption. To describe pathogenetic therapy features and follow-up. Materials and methods. The study included 12 patients (10 men and 2 women) aged 18 to 45 years (average age 29 years) with a diagnosis of B12-deficient myelopolyneuropathy induced by regular use of nitrous oxide. Results. The most common neurological complication of nitrous oxide abuse for more than 1 month was a generalized lesion of the peripheral nerves with acute or subacute distal symmetric sensory or sensorimotor axonal polyneuropathy. In the clinical picture, sensory complaints and disorders prevailed. Paresis developed in half of the cases. A typical neuroimaging symptom characteristic of funicular myelosis was rarely detected (16.7 %). A decrease in B12 vitamin level could most reliably be diagnosed only indirectly, by the presence of hyperhomocysteinemia (91.7 % of cases). In all cases that were followed-up, prolonged therapy with cyanocobalamin led to partial (n = 5; 62.5 %) or complete (n = 3; 37.5 %) regression of neurological symptoms. Conclusion. Caution regarding the use of nitrous oxide should be in all cases of predominantly sensory polyneuropathy with acute or subacute development in young and middle-aged people. A thorough history taking (targeted survey on the fact of nitrous oxide consumption) and diagnostics (testing the level of homocysteine, if possible methylmalonic acid) allow you to not miss a deficiency of vitamin B12, the treatment of the consequences of which with timely verification and adequate correction is quite effective. It is recommended that the level of homocysteine in the blood to be regularly monitored during the treatment (in order to achieve its normalization).

Review article: Clinical manifestations and outcomes of chronic nitrous oxide misuse: A systematic review

“…Most case series reported neurological complaints with 23 studies reporting presentations of sensory change, weakness or autonomic dysfunction, [17][18][19][20][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] whereas seven described psychiatric symptoms. 18,21,23,27,30,31,33 Other conditions reported included hyperpigmentation, 22,25,39 pruritis 25 and haematological sequelae.…”

“…Serum B12 levels were described in 21 case series [17][18][19][20][22][23][24][25][26][27][28][29]31,[33][34][35][36][37][38][39][40] with 243 reported values; of which 111 were low, 126 were normal and six were high. Homocysteine, MMA, haemoglobin and MCV were described in 19, [18][19][20][22][23][24][25][26][27][28][29][31][32][33][34][35][37][38][39] five 24,26,34,35,37 and 12, 18,20,[23][24][25]27,…”

“…MRI spine results were reported in 21 case series with dorsal column abnormalities demonstrated in 18 studies, [17][18][19][20][22][23][24][25]27,[29][30][31][32][33][34][37][38][39] lesions of unspecific location in one study 28 and two reported no cord lesion. 35,40 Cerebral white matter changes were identified in two case series.…”

“…B12 replacement therapy was reported in 18 case series. 17,19,20,22,24,25,[27][28][29][31][32][33][35][36][37][38][39][40] Two studies reported methionine replacement, 22,33 three provided physiotherapy, 22,37,38 whereas IVIG 27,35,37 and plasmapheresis 29 were also utilised on presentation or with poor clinical response. Additional therapies included antipsychotics, 21 pregabalin 17 and anticoagulation for pulmonary thromboembolism.…”

“…Ten case series reported complete recovery 20,24,28,32,33,35,[37][38][39][40] with 14 reporting partial recovery within their cohort. 17,19,22,24,25,28,29,32,33,[35][36][37][38][39][40] Two reported progression in the setting of continued N 2 O use 27,35 and one no recovery. 39 Outcomes were not reported in eight studies 18,21,23,26,27,30,31,34 and four studies reported patients lost to follow up.…”