Ozone therapy has been advertised as a treatment for wound healing, cancer, inflammatory conditions, infection, and wellness without scientific evidence. However, reports of neurotoxicity are sparse.

To present a patient with central nervous system toxicity associated with administration of intravenous ozone therapy.

Case report from a tertiary medical center.

A 40-year-old woman presented with visual loss, headache, and confusion. She had been receiving intermittent direct intravenous infusions of oxygen and ozone gas for genital herpes at a private clinic over the past several years. She initially received the ozone therapy via rectal insufflation, which was complicated by colonic perforation. The day prior to presentation, she had a typical intravenous treatment session that was complicated by a one-minute episode of loss of consciousness without a prodrome, followed by blurred vision, confusion, severe headache, and nausea. Her family brought her to the hospital for evaluation when her symptoms persisted the next day. MRI of the brain revealed T2 hyperintensity in the cerebellar white matter. She was admitted for observation and improved with symptomatic treatment over 24 hours. She was discharged home but did not return for follow up.

A syndrome featuring headache, visual loss, and encephalopathy is a potential complication of ozone therapy. Experiments in animal models have shown changes in cerebral vascular endothelial function in association with intravenous ozone therapy. Based on this possible pathogenesis, and resemblance to the clinico-radiographic syndrome, posterior reversible encephalopathy syndrome may represent the diagnosis