Neurological symptoms and signs occur in 30 to 40 per cent of patients with IE, are more frequent when IE is caused by S. aureus, and are associated with increased mortality rates.

Embolic stroke is the most common and clinically important of the neurological manifestations. Intra-cranial hemorrhage occurs in 5 per cent of patients with IE. Bleeding results from rupture of a mycotic aneurysm, rupture of an artery due to septic arteritis at the site of embolic occlusion, or hemorrhage into an infarct. Mycotic aneurysms, with or without rupture occur in 2 to 10 per cent of patients with IE: approximately half of these involve intracranial arteries. Cerebritis with microabscesses complicates IE caused by invasive, pathogens such as S. Aureus, but large brain abscesses are rare. Purulent meningitis complicates some episodes of IE caused by S. aureus or S. pneumoniae, but more typically the cerebrospinal fluid has an aseptic profile. Other neurological manifestations include severe headache (a potential clue to a mycotic aneurysm), seizure, and encephalopathy.