Factors affecting the topography of nitrous oxide-induced neurological complications.

Background: The factors underlying the topography of nitrous oxide (NO)-induced neurological complications are unknown.

Methods: We included all consecutive patients admitted to the university hospital of Marseille for NO-induced neurological complications in a prospective observational study. Patients underwent neurological examination, spinal cord magnetic resonance imaging, and nerve conduction studies within the first 4 weeks after admission.

Results: In total, 61 patients were included: 45% with myeloneuropathy, 34% with isolated myelopathy, and 21% with isolated neuropathy. On multivariable analysis, the odds of myelopathy were associated with the amount of weekly NO consumption (~600 g cylinder per week, odds ratio [OR] = 1.11, 95% confidence interval [CI] = 1.001-1.24). The extent of the myelopathy (number of vertebral segments) was correlated with the number of ~600-g cylinders consumed weekly (ρ = 0.40, p < 0.005). The odds of neuropathy were associated with the duration of consumption (per month; OR = 1.29, 95% CI = 1.05-1.58). Mean lower-limb motor nerve amplitude was correlated with the duration of consumption (in months; ρ = -0.34, p < 0.05).

Conclusions: The odds of myelopathy increased with the amount of NO consumption, and the odds of neuropathy increased with the duration of NO exposure, which suggests distinct pathophysiological mechanisms underlying these two neurological complications.