Nitrous oxide-related neurotoxicity: Clinical features, key investigations, and a proposed diagnostic approach from a single-center cohort.

Background: Recreational use of nitrous oxide (N Methods: We conducted a retrospective study of 52 consecutive patients diagnosed with N Results: The median age was 24.0 [21.8;28.0] years, with a female-to-male ratio of 1.7:1. Acute onset (< 4 weeks) was observed in 61.5% of cases. Sensory symptoms occurred in 94.2% and gait ataxia in 86.5%, with 88.5% exhibited a pattern of distal weakness exceeding proximal. Elevated homocysteine was present in 43 (89.6%), whereas low total B12 was found in only 10.4%. MRI abnormalities were detected in 31/48 (64.6%), with the "inverted V" sign in 17 cases (54.8%). Reduced CMAPS with intact sensory potentials was the most common EDX pattern 17 (32.7%), and needle electromyography showed ongoing denervation in 66%. Exploratory association analyses did not identify any significant relationships between EDX classifications, MRI findings, symptom onset, or homocysteine levels. Conclusion: Nitrous oxide neurotoxicity is characterized by predominant sensory symptoms, gait ataxia and elevated homocysteine. EDX patterns are heterogenous and non-specific. A combined approach using spinal MRI, serum homocysteine and EDX could play a key role in differentiating this pathology from other mimickers and achieving a timely and accurate diagnosis.