ABSTRACT
BACKGROUND: The recreational use of nitrous oxide (N2O) has gained popularity over recent years. We present a case series of excessive N2O users with neurological complications. METHODS: In this retrospective three-centre study, we used a text mining algorithm to search for patients who used N2O recreationally and visited a neurologist. RESULTS: We identified 251 patients. The median duration of N2O use was 11 months (interquartile range [IQR], 3-24) and the median amount of N2O used per occasion 1.6 kg (IQR 0.5-4.0). Clinically, polyneuropathy (78%), myelopathy (41%), and encephalopathy (14%) were the most common diagnoses. An absolute vitamin B12 deficiency of < 150 pmol/L was found in 40% of cases. In 90%, at least one indicator of functional vitamin B12 status (vitamin B12, homocysteine, or methylmalonic acid) was abnormal. MRI showed signs of myelopathy in 30/55 (55%) of cases. In 28/44 (64%) of those who underwent electromyography, evidence of axonal polyneuropathy was found. Most (83%) patients were treated with vitamin B12 supplementation, and 23% were admitted to the hospital. Only 41% had follow-up for ≥ 30 days, and 79% of those showed partial or complete recovery. CONCLUSIONS: In this case series of excessive N2O users, we describe a high prevalence of polyneuropathy, myelopathy, and encephalopathy. Stepwise testing for serum levels of vitamin B12, homocysteine, and methylmalonic acid may support the clinical diagnosis. Due to low sensitivity, MRI of the spinal cord and electromyography have limited value. Effective treatment should incorporate supplementation of vitamin B12 and strategies to prevent relapses in N2O use.
Subject(s)
Brain Diseases , Polyneuropathies , Spinal Cord Diseases , Vitamin B 12 Deficiency , Humans , Nitrous Oxide/adverse effects , Retrospective Studies , Methylmalonic Acid , Spinal Cord Diseases/chemically induced , Spinal Cord Diseases/diagnostic imaging , Spinal Cord Diseases/drug therapy , Vitamin B 12 Deficiency/chemically induced , Vitamin B 12 Deficiency/drug therapy , Vitamin B 12 , Brain Diseases/chemically induced , Homocysteine , Polyneuropathies/drug therapyABSTRACT
Nitrous oxide, laughing gas, is used as a party drug to achieve a euphoric effect. It has been gaining popularity in recent years and is considered a relatively innocent substance. Nitrous oxide is known to cause subacute degeneration of the spinal cord by inactivation of active vitamin B12. Vitamin B12 plays an essential role in the synthesis of myelin. Hence, vitamin B12 deficiency can lead to degeneration of the dorsal and lateral columns of the spinal cord. Polyneuropathy is a less known complication. We present a 17-year-old woman and a 19-year-old man with subacute axonal polyneuropathy caused by laughing gas abuse. Abstinence of laughing gas and treatment with intramuscular and oral vitamin B12 suppletion respectively have led to improvement of their symptoms. Our cases demonstrate a less-known but treatable complication of laughing gas.
