Inhaled nitrous oxide-induced functional B12 deficiency

A recent surge of nitrous oxide misuse around London which merits a public health warning

BACKGROUND

Use of nitrous oxide (N2O) gas for recreational purposes by young people is increasingly recognized as a public health hazard in the UK.

METHODS

We looked at the hospital records of patients admitted over the last 4 years to a single neurological centre in Essex to determine the demographics, presentation, and management of patients presenting with symptoms of N2O toxicity from its recreational use.

RESULTS

Of the 17 patients (mean age = 22.9 ± 3 years) admitted between September 2018 and October 2022, 70% were admitted between January and October 2022. All patients reported limb paraesthesiae and 16/17 reported (95%) imbalance; 11/17 (65%) showed objective limb weakness. Serum B12 concentration was low in 9/17 (53%). Plasma methylmalonic acid (n = 7) and homocysteine (n = 8) levels were elevated in all patients tested. Spinal cord Magnetic Resonance Imaging (MRI) imaging was abnormal in 10/17 (59%) patients. Nerve conduction studies were abnormal in 10/13 (77%) patients, with evidence of a symmetric, length-dependent, large fibre neuropathy.

CONCLUSIONS

There has been a recent surge of cases with neurological complications of recreational N2O abuse in the UK, with a relatively greater rate in 2022. Greater awareness of this condition amongst clinicians and health regulators is urgently required to prevent harm from N2O misuse in young people.

Severe length-dependent peripheral polyneuropathy in a patient with subacute combined spinal cord degeneration secondary to recreational nitrous oxide abuse: A case report and literature review

Nitrous oxide abuse can have detrimental effects on the central and peripheral nervous systems. This case study report aims to demonstrate a combination of severe generalized sensorimotor polyneuropathy and cervical myelopathy related to vitamin B₁₂ deficiency following nitrous oxide abuse. We present a clinical case study and literature review examining primary research-published between 2012 and 2022-reporting nitrous oxide abuse affecting the spinal cord (myelopathy) and peripheral nerves (polyneuropathy); 35 articles were included in the review with a total of 96 patients, where the mean "patients" age was 23.9 years and were in a 2:1 male/female ratio. Of the 96 cases, within the review, 56% of patients were diagnosed with polyneuropathy, most commonly impacting the nerves of the lower limb (62%), while 70% of patients were diagnosed with myelopathy, most commonly impacting the cervical region (78%) on the spinal cord. In our clinical case study, a 28-year-old male underwent a multitude of diagnostic investigations for bilateral "foot drop" and sense of lower limb stiffness as ongoing complications of a vitamin B₁₂ deficiency secondary to recreational nitrous oxide abuse. Both the literature review and our case report emphasize the dangers of recreational nitrous oxide inhalation, colloquially termed "nanging" and the risks it presents to both the central and peripheral nervous systems, which is erroneously considered by many recreational drug users to be less harmful than other illicit substances.

Important reminder: nitrous oxide (N2O) as a cause of functional vitamin B12 deficiency

A 32-year-old woman who misused multiple substances, including nitrous oxide (N₂O), sought medical advice after she subacutely developed bilateral lower extremity weakness without a sensory level but with ataxia-her significant other developed similar symptoms with vitamin B₁₂ deficiency due to N₂O intake. Laboratory results revealed macrocytic anaemia despite normal B₁₂ and folate levels, with serum markers pointing towards functional cobalamin deficiency. Spinal MRIs and cerebrospinal fluid analysis were unremarkable. Our patient was treated with vitamin B₁₂ supplementation with an encouraging response.