Analysis of clinical characteristics and prognostic factors in 110 patients with nitrous oxide abuse

Abstract

Purpose: To review the clinical symptoms, auxiliary examination findings, and outcomes of patients with nitrous oxide (N₂ O) abuse, and analyze the factors that affect outcomes.

Methods: Patients with N₂ O abuse treated in the Department of Neurology between January 2018 and December 2020 were included. The clinical data of these patients were collected, and follow-up was conducted to determine the outcomes.

Results: The average age of the 110 patients with N₂ O abuse was 21.4 ± 4.2 years (range: 14-33 years). Clinical presentation primarily included neurological symptoms, such as limb numbness and/or weakness (97%), psychiatric symptoms, changes in appetite, and skin hyperpigmentation. Laboratory test results were characterized by vitamin B₁₂ deficiency (60%, 34 out of 57 cases) and high homocysteine level (69%, 31 out of 45 cases). Electromyography indicated mixed axonal and demyelination injury (92%, 80 out of 87 cases). Motor and sensory nerves were simultaneously involved, and injury primarily involved the lower limbs. One hundred and seven (97%) patients were clinically diagnosed with peripheral neuropathy, of whom 26 (24%) exhibited spinal abnormalities on magnetic resonance imaging, supporting a diagnosis of subacute combined degeneration. Treatment included N₂ O withdrawal and vitamin B₁₂ supplementation. Reexamination of six patients indicated that treatment was effective. Follow-up was completed for 51 patients. Thirty-four patients (67%) recovered completely, 17 patients (33%) had residual limb numbness, and only one patient experienced relapse. Sex was an independent prognostic factor; the outcomes of female patients were better than that of male patients.

Conclusion: The recreational use of N₂ O has largely expanded among youth in recent decades, which has become a growing public health concern in China. It highlights the importance of the recognition of various clinical symptoms, particularly limb numbness and/or weakness related to the cases of N₂ O abuse. The therapeutic administration of vitamin B₁₂ supplementation and N₂ O withdrawal can make the overall prognosis good, especially for female patients.

Keywords: clinical characteristics; nitrous oxide; outcomes; peripheral neuropathy; vitamin B12 deficiency.

FIGURE 1

Spinal magnetic resonance imaging. (a–d) Transverse sections of spinal cord showing “V,” inverted “V,” triangle, and elliptical signals. (e–h) Sagittal sections showing high T2 signal lesion involving the dorsal longitudinal segment of the spinal cord

FIGURE 2

Changes in vitamin B₁₂ and homocysteine (HCY) levels in patients with nitrous oxide abuse

FIGURE 3

(a, c) Magnetic resonance image (MRI) examination of patients with nitrous oxide abuse at initial consultation showed increased T2 signal in the spinal cord at the C3–C6 level. (b, d) MRI reexamination after 1 month showed reduction of increased T2 signal in the spinal cord at the C3–C6 level

FIGURE 4

Changes in compound muscle action potential (CMAP) and motor nerve conduction velocity (MNCV) in patients with nitrous oxide abuse