Some patients exhibit cryptogenic brain abscess (CBA) in the absence of any such congenital disease or other infections. Patent foramen ovale (PFO) is a very common disease that exhibits right-to-left shunt.

CBA might be caused by paradoxical embolization of a bacterial mass via PFO. Thus, more patients with CBA need to undergo transesophageal echocardiography (TEE) to detect PFO.