Nitrous oxide-induced neurotoxicity: Clinical characteristics and impacts on overall neurological impairments

Objective: The reports of the recreational use of nitrous oxide (N₂O) and its related neuropathy are increasing. However, it is unclear whether specific clinical characteristics are associated with the overall neurological impairments among these individuals.

Methods: We retrospectively included 20 hospitalized patients with N₂O-related neurological complaints between January 2016 and March 2021 at the West China Hospital of Sichuan University. Detailed demographic, clinical features, lab tests, and imaging data were collected. A functional disability rating score (FDRS) was calculated to determine the degree of neurological impairment. The relationships between the aforementioned factors and the FDRS sum score were explored.

Results: These individuals were aged between 16 and 30 years (mean ± SD: 21.90 ± 4.06). At admission, unsteady gait (95%, nineteen of twenty), weakness (95%, nineteen of twenty), and limb paresthesia (70%, fourteen of twenty) were the most common symptoms; decreased deep tendon reflexes (100%, nineteen of nineteen), reduced muscle strength (95%, nineteen of twenty), and impaired coordination (95%, nineteen of twenty) were frequently found. The FDRS sum scores ranged from 3 to 12. Among all the factors, admission from the emergency room (p = 0.033), decreased hemoglobin (p = 0.004) (without previous VitB12 supplements), decreased red blood cell (RBC) count (p = 0.004) (without previous VitB12 supplements), and increased mean corpuscular volume (p = 0.036) (with previous VitB12 supplements) positively correlated with the FDRS sum score.

Conclusion: Nitrous oxide (N₂O) could lead to severe neurological impairments among users. Abnormal RBC indicators at admission may be associated with a worse clinical presentation and need further attention. Population education about the consequences of N₂O consumption and control measures concerning access to N₂O should be further emphasized.