Undiagnosed patent foramen ovale presenting as a cryptogenic brain abscess: case report and review of the literature.

A 43-year-old man with no significant medical history but poor oral hygiene presented with fever and new-onset tonic-clonic seizures secondary to a left parieto-occipital brain abscess defined by computed tomography, magnetic resonance imaging, and surgical evacuation. A comprehensive workup looking for a source of infection was unremarkable including computed tomography of the chest, abdomen, and pelvis; blood cultures; and a tagged white blood cell scan. A transesophageal echocardiogram bubble study revealed the presence of a patent foramen ovale (PFO) but no other abnormalities. Culture of the material obtained at surgery revealed flora commonly found in the oropharynx that responded to antibiotic therapy. A review of the literature revealed three other cases in which a brain abscess from flora commonly found in the oropharynx was associated with a PFO. We hypothesize that the underlying mechanism is a significant bacterial load from poor dentition that enters the arterial circulation through a PFO and forms the nidus for a brain abscess. Surgical evacuation is the preferred method for diagnosis and initial treatment. If a brain abscess is identified without any adjacent source of infection, a recent head trauma, or a neurosurgical procedure, then a transesophageal echocardiogram is indicated to exclude a PFO. If a PFO is found, then hematogenous spread of flora normally found in the oropharynx through a right to left shunt should be suspected. Surgical evacuation followed by intravenous antibiotics specific to the identified organisms is warranted. Once the infection is eliminated, anatomic closure of the PFO with good oral hygiene practices may be the best course of action for preventing recurrences.