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Infectious disease and microbiology – Mycotic aneurysms
Mycotic aneurysms are infected aneurysms of blood vessels that arise as part of an infectious process, most commonly infective endocarditis (IE). Despite the name, “mycotic” refers to the fungus-like shape of the aneurysm, not the cause, which is usually bacterial.
These aneurysms may be intracranial or extracranial, and they can also occur due to infection of a preexisting aneurysm or arterial wall (microbial arteritis).
Epidemiologically, about 2–4% of patients with infective endocarditis develop intracranial mycotic aneurysms, although the true incidence is likely underestimated due to asymptomatic cases. The prevalence in the general population is unknown but has decreased in the antibiotic era.
Major risk factors include:
Clinically, many patients are asymptomatic until complications occur.
Symptoms depend on location:
Diagnosis relies on a combination of laboratory tests and imaging.
Treatment involves prolonged intravenous antibiotics (at least 6–8 weeks) tailored to the identified organism.
Some patients, especially those with intracranial aneurysms, may improve with antibiotics alone.
Surgical or endovascular intervention is required in cases of:
The prognosis is serious, with mortality depending on rupture status:
Mycotic aneurysms are infected aneurysms of blood vessels that arise as part of an infectious process, most commonly infective endocarditis (IE). Despite the name, “mycotic” refers to the fungus-like shape of the aneurysm, not the cause, which is usually bacterial.
These aneurysms may be intracranial or extracranial, and they can also occur due to infection of a preexisting aneurysm or arterial wall (microbial arteritis).
Epidemiologically, about 2–4% of patients with infective endocarditis develop intracranial mycotic aneurysms, although the true incidence is likely underestimated due to asymptomatic cases. The prevalence in the general population is unknown but has decreased in the antibiotic era.
Major risk factors include:
- Infective endocarditis
- Intravenous drug use
- Arterial trauma
- Contiguous infections near blood vessels
- Immunosuppression and advanced age
- Septic emboli from cardiac vegetations lodging in vessels
- Bacteremic seeding of damaged arterial intima
- Direct spread from nearby infections
- Direct inoculation from trauma or procedures
Clinically, many patients are asymptomatic until complications occur.
Symptoms depend on location:
- Intracranial aneurysms: headache, fever, stroke-like symptoms, seizures
- Aortic aneurysms: abdominal or back pain, fever
- Rupture: sudden deterioration, bleeding, shock
Diagnosis relies on a combination of laboratory tests and imaging.
- Blood cultures are positive in 50–85% of cases
- Elevated white blood cell count and anemia are common
- Conventional angiography is the gold standard
- CT, MRI, and Doppler ultrasound help localize and assess the aneurysm
Treatment involves prolonged intravenous antibiotics (at least 6–8 weeks) tailored to the identified organism.
Some patients, especially those with intracranial aneurysms, may improve with antibiotics alone.
Surgical or endovascular intervention is required in cases of:
- Rupture or bleeding
- Enlarging aneurysm despite therapy
- High-risk anatomical locations
The prognosis is serious, with mortality depending on rupture status:
- ~30% mortality if aneurysm is intact
- Up to 80% mortality if rupture occurs
- Hemorrhage (e.g., subarachnoid hemorrhage)
- Embolization
- Vascular insufficiency
- Shock and death
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