Ozone therapy via autohemotherapy has become among the alternative therapies purported to treat chronic lymphocytic leukemia. Ozone gas is injected into blood drawn from the patient, which is mixed then transfused back intravenously. Due to the infrequent use of this modality, it has not been previously reported as a risk factor for stroke.

A 62-year-old man with a history of chronic lymphocytic leukemia, chronic migraines, hypertension, and diabetes mellitus type II presented with acute left arm numbness followed by weakness during administration of intravenous (IV) ozone. Shortly after, he developed a migrainous headache, which is typical for him. Neurological examination revealed left upper and lower extremity weakness. CT head and CT angiography were performed and were unremarkable. The patient was treated with IV tPA. He continued to have left-sided weakness and numbness along with a migrainous headache after the intervention. MRI of the brain revealed multiple bilateral frontal and parietal infarcts. Dual antiplatelet therapy was initiated.  Echocardiogram revealed a large patent foramen ovale (PFO) with a right-to-left shunt. A transcranial doppler with bubble study revealed multiple high intensity transient signals post valsalva maneuvers, supporting the diagnosis of paradoxical emboli. Patient eventually underwent successful outpatient PFO closure without complications.

This case presents a rare cause of stroke following IV injection of ozone. Acute stroke following ozone therapy has not been previously reported in the literature. The pathogenesis remains unknown, although it is theorized that it may have been due to IV administration of ozone-mixed blood in the presence of a PFO. It is imperative to recognize this phenomenon as a potential risk of embolic stroke in patients receiving IV ozone treatment.