Myeloneuropathy and Macrocytosis Associated With Nitrous Oxide Abuse

• After four months of excessive nitrous oxide (N₂O) exposure, a dentist had myeloneuropathy with spastic paraparesis, Lhermitte's sign, sensory shading, loss of position and vibration sense, ataxia, and impotence. Macrocytosis, hypersegmented neutrophils, and a reduced vitamin B₁₂ level were associated with normal findings on gastric analysis and Schilling test. Complete hematologic and neurologic recovery followed N₂O avoidance and vitamin therapy for six months.