Cerebral Septic Embolism: Clinical Implications and Management

Pathophysiology and Causes

Cerebral septic emboli most commonly result from hematogenous spread, typically originating from infective endocarditis (IE), where septic microemboli travel to the vasa vasorum or lodge at distal branching points in cerebral vessels 1
The predominant cerebral insult from septic emboli is ischemic stroke, but may also include intracerebral hemorrhage (either subarachnoid or subdural), infectious aneurysm, brain abscess, and rarely meningitis 2
Most common causative organisms are Staphylococcus aureus and viridans group streptococci, though other pathogens like enterococci, coagulase-negative staphylococci, and HACEK group organisms can also cause cerebral septic emboli 1

Up to 40% of patients with infective endocarditis present with clinically evident neurological sequelae, but brain MRI studies have identified embolic lesions in as many as 60-80% of IE patients 2
Patients may initially present with symptoms of ischemic stroke in the territory of the occluded vessel, though such strokes can be clinically silent depending on the brain region affected 1
Focal neurological deficits are a common presentation of cerebral septic emboli 1
Headache, especially severe and unremitting, is a possible symptom of cerebral septic emboli 1
Seizures can occur as a result of cerebral septic emboli 1
Meningeal signs may occur if rupture into the meninges occurs 1

Mycotic (infectious) aneurysms occur in 2-4% of IE cases but may be more common due to asymptomatic presentations 3
These aneurysms are typically thin-walled and friable with a high tendency to rupture and hemorrhage 3
Unlike congenital berry aneurysms, the size of infectious cerebral mycotic aneurysms is not a reliable predictor of rupture risk 1

Brain imaging is mandatory for any suspicion of neurological complications in patients with IE or other risk factors for septic emboli 3
MRI with gadolinium contrast offers higher sensitivity than CT in detecting cerebral lesions and may influence clinical management 3
Vascular imaging (CT angiography or conventional angiography) should be performed to identify potential mycotic aneurysms in patients with neurological symptoms 3

Prompt diagnosis and initiation of appropriate antimicrobial therapy are crucial for preventing first or recurrent neurological complications 3
For patients with IE and silent cerebral embolism or transient ischemic attack, cardiac surgery (if indicated) should be performed without delay 3
After an intracerebral hemorrhage, cardiac surgery should generally be postponed for at least one month 3
Neurosurgical or endovascular treatment is recommended for large, expanding, or ruptured intracranial infectious aneurysms 3

Cerebral embolic events pose an independent risk factor for mortality in IE, even when subclinical 2
Patients with neurological complications tend to have higher morbidity and mortality compared to those without such complications 4

The risk of embolism in IE is highest during the first 2 weeks of antibiotic therapy and is clearly related to the size and mobility of the vegetation 5