Patent foramen ovale as a risk factor for cryptogenic brain abscess: case report and review of the literature.

We encountered a patient with brain abscess presumably caused by dental infection. The patient displayed patent foramen ovale (PFO) and a giant Eustachian valve, through which spontaneous right-to-left shunt was revealed by transesophageal echocardiography. Reviewing the literature, we find additional cases where brain abscess originated from an increased amount of flora commonly found in the oral cavity that bypassed the pulmonary vascular bed and the lymphatic system through PFO. Additionally, a Eustachian valve should be considered an adjunctive risk factor for initiating a spontaneous right-to-left shunt and predisposing cryptogenic brain abscess in patients with PFO.