Vitamin B12 Status in Recreational Users of Nitrous Oxide: A Systematic Review Focusing on the Prevalence of Laboratory Abnormalities

Neurological disorders caused by recreational use of nitrous oxide-a retrospective study from a German metropolitan area and review of the literature

BACKGROUND

The recreational use of nitrous oxide (N2O) has seen a worldwide rise in the recent years, resulting in an increased incidence of neurological complications due to N2O-induced functional vitamin B12 deficiency. Here, we report on a cohort of patients admitted to a tertiary care center with neurological symptoms in the context of recreational N2O use between 2020 and 2024.

METHODS

We screened the database of the University Hospital Frankfurt for patients ≥ 18 years of age who presented with neurological deficits and a history of N2O consumption between January 2020 and December 2024. We analyzed the spectrum of neurological deficits as well as radiological and laboratory findings.

RESULTS

We identified a total of 20 patients, 16 males and 4 females, with a median age of 21 years. We found a steady increase in the number of cases, with no cases in 2020 and 2021 and a definite peak in 2024. The mean daily N2O consumption was 2500 g. All patients reported sensory deficits; 85% had gait disturbances and 70% had motor deficits. Less frequent symptoms included pain, bladder or bowel dysfunction, fatigue and spasticity. The median score on the modified Rankin scale (mRS) was 2, with some patients being wheelchair-bound. The most frequently observed lesion pattern was combined myelo-polyneuropathy. T2-hyperintense myelon lesions were observed in 11 of 15 patients (73.3%). Surprisingly, laboratory work-up revealed normal vitamin B12 levels in nearly all patients (95%), whereas homocysteine and methylmalonic acid levels were prominently elevated in all patients (100%). In addition, 13 patients (65%) presented with hematological abnormalities. All of the patients who presented for follow-up (20%) reported continued use of N2O. There was no neurological improvement in any of these cases.

CONCLUSIONS

Our study confirms that the increasing incidence of N2O-induced neurotoxicity reported in other countries can also be observed in Germany. Therefore, it underlines the relevance of the current debate on health policies. In addition, our study highlights the pitfalls of vitamin B12 laboratory testing and emphasizes the need to address substance addiction in treatment.

Severe subacute combined degeneration of the spinal cord resulting from nitrous oxide (N2O) abuse: a case series

OBJECTIVE

To describe the demographic, clinical, laboratory, and radiological findings, and the clinical course of seven patients with severe N2O-induced subacute combined degeneration of the spinal cord (SACD).

METHODS

Retrospective study with prospective follow-up of patients with SACD associated with N2O abuse presenting at a single center between 2014 and 2024.

RESULTS

The median age (range) of the seven patients (one woman, six men) was 24 (18-33) years. Prior to disease onset, patients had consumed N2O daily over a median (range) of 12 (3-20) weeks, with a mean (SD; range) inhalation dosage of 2376.7 (2872.7; 160-9000) g of N2O per day. Clinical presentations included paresthesia and paresis in the legs and gait disturbances. All patients exhibited characteristic signal alterations in the posterior columns spanning from C1 to T10 on T2-weighted spinal MRIs. Electrophysiology demonstrated polyneuropathies in all but one patient. Vitamin B12 levels were decreased in four, but normal in three patients. Methylmalonic acid levels were elevated in all patients. Although the median (interquartile range [IQR]) modified Rankin Scale score improved from 3.0 (3.0-4.0) at baseline to 1.0 (1.0-2.0; p < 0.05, Wilcoxon matched-pairs signed-rank test) at follow-up after the start of vitamin B12 supplementation, all five patients who could be examined on follow-up exhibited persistent deficits on the last follow-up assessment at a median (range) of 5 (3-116) months after disease onset.

CONCLUSIONS

N2O abuse over a few weeks can lead to severe SACD. The diagnosis is supported by characteristic findings on spinal MRI and elevated methylmalonic acid levels, while normal vitamin B12 levels do not rule out N2O-induced SACD. Although there was some clinical improvement upon cessation of N2O abuse and vitamin B12 supplementation, residual deficits persisted.

Increase of nitrous oxide-induced neurological disorders - a German multicenter experience

BACKGROUND

Nitrous oxide (N₂O), commonly known as laughing gas, is widely recognized for its anesthetic and analgesic effects, and is frequently used in medical contexts. However, its misuse can lead to significant neurological complications, which are often under-recognized in clinical practice. Recent data on such cases in Germany are rare. We here report the spectrum of neurological complications associated with the recreational use of N₂O, as encountered in German neurology centers.

METHODS

We retrospectively analyzed of 23 cases presenting with neurological symptoms following N₂O abuse between July 2020 and August 2024 across five neurology departments in Germany. Data were collected on patient demographics, clinical manifestations, diagnostic findings, and treatment approaches.

RESULTS

Over the last four years the number of cases increased. Clinical presentations primarily included neuropathy, found in all patients, along with myelopathy. The most common symptoms were sensory loss, ataxia, and motor deficits.

CONCLUSION

Our data suggest that N₂O abuse is on the rise in Germany. Further initiatives are warranted to raise awareness among users, healthcare and professionals.

Correlation Between Nitrous Oxide and Functional Vitamin B12 Deficiency Resulting in Subacute Combined Degeneration of the Spinal Cord: A Case Report

Nitrous oxide (N2O) is generally used in the medical and food industries. However, it is sometimes illegally misused by young adults as a recreational drug. In either of these uses, functional vitamin B12 deficiency results in neurological implications, such as peripheral neuropathy and subacute combined degeneration (SACD). Here, we report a case of N2O-induced SACD, in which a diagnosis of functional B12 deficiency was made based on borderline normal serum vitamin B12 levels with elevated metabolites (methylmalonic acid and homocysteine). In this case, treatment with intramuscular (IM) vitamin B12 led to significant clinical improvement.

Enhancing Differential Diagnosis Related to Oxidative Stress, Nitrous Oxide, and Nutrition by Rapid Plasma Homocysteine Measurement

BACKGROUND

Historically used as a marker for inherited disorders, the current interest in plasma homocysteine measurement lies in its ability to provide valuable information about the metabolic and nutritional status of patients. Specifically, nitrous oxide (N2O) abuse can lead to functional vitamin B12 deficiency by oxidation and increase oxidative stress, resulting in elevated plasma homocysteine levels, which mimic neurological conditions such as Guillain-Barré syndrome. Rapid identification of hyperhomocysteinemia is crucial for timely intervention and avoiding costly, unnecessary treatments.

OBJECTIVE

This study evaluates the performance of a rapid immunoassay technique (Snibe) compared to mass spectrometry (LC-MS/MS) for measuring plasma homocysteine levels in patients with nitrous oxide abuse and non-inherited caused of elevated homocysteine, aiming to enhance differential diagnosis related to oxidative stress.

METHODS

235 patients from Lille University Hospital were included. EDTA blood samples were collected and analyzed using both rapid immunoassay (Snibe) and LC-MS/MS. Neurological assessment was performed using the peripheral neuropathy disability (PND) score.

RESULTS

Firstly, significant elevations in plasma homocysteine levels were observed in patients abusing nitrous oxide measured by LC-MS/MS. Secondly, the immunoassay provided rapid results, essential for early clinical decision-making, but tended to underestimate high values compared to LC-MS/MS. A good correlation was found between the methods for low and moderate values.

CONCLUSION

The immunoassay tended to underestimate high-value samples compared to LC-MS/MS, which is a common problem with the competitive methodology. The rapid immunoassay technique is effective for initial screening and early intervention, aiding in the differential diagnosis of conditions related to oxidative stress. Therefore, it is recommended to use the CLIA method for initial screening and confirm with mass spectrometry if there are abnormal samples. Integrating both techniques can enhance diagnostic accuracy and improve patient outcomes.

Recreational nitrous oxide and thrombotic events: a case series

Background

The study aimed to elucidate the prevalence of nitrous oxide (N2O) usage in patients with unexplained venous thromboembolism (VTE), highlighting the potential association with hyperhomocysteinaemia (HHcy).

Methods

We conducted a retrospective study at the Royal London Hospital, examining cases of N2O-related VTE from March to August 2023. Among 50 patients identified, four (8%) had recent unprovoked VTE. Patient data were collected based on N2O ambulatory emergency care pathway admissions.

Results

Among the 50 patients identified, four (8%) had recent or concurrent VTE. Three were male (75%), with an ethnic distribution of 50% Asian or Asian British and 50% Black or Black British. Patients were distributed across quintiles of the index of multiple deprivation. All had actual or functional vitamin B12 deficiency.

Discussion

The association between N2O use and VTE requires further investigation, though a plausible mechanism involving HHcy has been proposed. Clinicians should be vigilant for VTE in N2O users, especially those presenting with unexplained symptoms. VTE prophylaxis may be worth considering, particularly if continued exposure to nitrous oxide is anticipated.

Conclusion

N2O misuse may increase the risk of VTE, warranting attention from healthcare providers. Further research is needed to elucidate this association and inform preventive strategies. Public awareness about the risks of N2O remains essential.

Cracking the Whippet: The Inconsistent Treatment of Myeloneuropathy Secondary to Chronic Nitrous Oxide Misuse

Background The recreational abuse of nitrous oxide (N2O) is becoming increasingly prevalent within the United Kingdom and across the globe. Chronic abuse can cause nerve and spinal cord damage through the functional inactivation of vitamin B12. We present six cases from a single centre in the United Kingdom between 2016 and 2020 with neurological complications from N2O abuse, ranging from paraesthesia to subacute combined degeneration of the spinal cord. Methodology A retrospective review of all neurology admissions to Queen Elizabeth Hospital Birmingham (QEHB) between 2016 and 2020 was conducted to identify patients admitted with a diagnosis of neurological dysfunction (neuropathy or myelopathy) in association with chronic N2O misuse. The Prescribing Information and Communication System was used to collect data on demographics, reported N2O misuse, presenting symptoms, results of blood tests, nerve conduction studies and treatment regimens. All patients gave verbal consent for inclusion in the case series. Data were anonymised and analysed by the corresponding author. Results All patients were males aged between 22 and 28 years. In all cases, the patients were admitted with the abuse of N2O whippet canisters (ranging from 20 to 500 canisters per session), presenting with a combination of sensory and motor disturbance. Clinical suspicion, in the context of a history of N2O abuse, along with elevated blood concentrations of methylmalonic acid (MMA) and homocysteine, and nerve conduction studies, was the cornerstone of the diagnosis. All patients were treated with parenteral vitamin B12, though individual regimens differed, with no standardisation in the duration or frequency of treatment. All patients received intramuscular (IM) vitamin B12 injections during admission, with one patient receiving oral vitamin B12 before being switched to IM vitamin B12 injections. One patient received additional folic acid as a treatment adjunct. Prescriptions were most varied on discharge with huge discrepancies in duration and frequency of vitamin B12 replacement, ranging from no B12 replacement at all to IM injections once weekly for eight weeks.  Conclusions The variability in route, dose and duration of vitamin B12 treatment, along with the variable use of adjunctive therapy reported in the literature, highlights the current lack of consensus in managing N2O neurotoxicity.