Infectious intracranial aneurysm

An infectious intracranial aneurysm (IIA, also called mycotic aneurysm) is a cerebral aneurysm that is caused by infection of the cerebral arterial wall.

Etiology

Most IIAs are caused by bacterial infection, most commonly Staphylococcus aureus and Streptococcus species. In most cases the infection originates from left-sided bacterial endocarditis.^[1] Other common sources include cavernous sinus thrombosis, bacterial meningitis, poor dental hygiene and intravenous drug use.

Signs and symptoms

Many patients with unruptured IIA may have no symptoms. In patients who do have symptoms these are often related to rupture of the aneurysm and to its cause.^[1] Rupture of an IIA results in subarachnoid hemorrhage, symptoms of which include headache, dizziness, seizures, altered mental status and focal neurological deficits.

In contrast to other cerebral aneurysms, large aneurysm size does not increase the chance of rupture. Small IIAs tend to have high rupture rates, while larger IIAs more commonly cause symptoms due to pressure on the surrounding brain tissue.

Diagnosis

Diagnosis of IIA is based on finding an intracranial aneurysm on vascular imaging in the presence of predisposing infectious conditions.^[1] Positive bacterial cultures from blood or the infected aneurysm wall itself may confirm the diagnosis, however blood cultures are often negative. Other supporting findings include leukocytosis, an elevated erythrocyte sedimentation rate and elevated C-reactive protein in blood.

Treatment

Treatment depends on whether the aneurysm is ruptured and may involve a combination of antimicrobial drugs, surgery and/or endovascular treatment.^[1]

Prognosis

Mortality of IIA is high, unruptured IIA are associated with a mortality reaching 30%, while ruptured IIA has a mortality of up to 80%.^[1] IIAs caused by fungal infections have a worse prognosis than those caused by bacterial infection.^[2]

Epidemiology

IIAs are uncommon, accounting for 2.6% to 6% of all intracranial aneurysms in autopsy studies.^[2]

References

1 2 3 4 5 Ducruet, AF; Hickman, ZL; Zacharia, BE; Narula, R; Grobelny, BT; Gorski, J; Connolly ES, Jr (January 2010). "Intracranial infectious aneurysms: a comprehensive review.". Neurosurgical review 33 (1): 37–46. doi:10.1007/s10143-009-0233-1. PMID 19838745.
1 2 Clare, CE; Barrow, DL (July 1992). "Infectious intracranial aneurysms.". Neurosurgery clinics of North America 3 (3): 551–66. PMID 1633479.

Cerebrovascular diseases (G45–G46 and I60–I69, 430–438)

Brain ischemia/
cerebral infarction
(ischemic stroke/TIA)

TACI, PACI	precerebral: Carotid artery stenosis cerebral: MCA ACA Amaurosis fugax Moyamoya disease

POCI	precerebral: Anterior spinal artery syndrome Vertebrobasilar insufficiency Subclavian steal syndrome brainstem: medulla Medial medullary syndrome Lateral medullary syndrome pons Medial pontine syndrome/Foville's Lateral pontine syndrome/Millard-Gubler midbrain Weber's Benedikt Claude's cerebral: PCA Lacunar stroke Dejerine–Roussy syndrome cerebellar

General	cerebral: Cerebral venous sinus thrombosis CADASIL Binswanger's disease Transient global amnesia

Intracranial hemorrhage
(hemorrhagic stroke)

Extra-axial	Epidural Subdural Subarachnoid

Cerebral/Intra-axial	Intraventricular

Brainstem	Duret haemorrhage

Aneurysm

Cerebral aneurysm
- Intracranial berry aneurysm
- Charcot-Bouchard aneurysm

Other/general

Cerebral vasculitis

Arteries, arterioles
and capillaries

Inflammation

Arterial occlusive disease /
peripheral artery disease

Arteriosclerosis	Atherosclerosis Foam cell Fatty streak Atheroma Intermittent claudication Critical limb ischemia Monckeberg's arteriosclerosis Arteriolosclerosis Hyaline Hyperplastic Cholesterol LDL Oxycholesterol Trans fat

Stenosis	Carotid artery stenosis Renal artery stenosis

Other	Aortoiliac occlusive disease Degos disease Erythromelalgia Fibromuscular dysplasia Raynaud's phenomenon

Aneurysm / dissection /
pseudoaneurysm

Vascular malformation

Vascular nevus

Veins

Inflammation	Phlebitis

Venous thrombosis / Thrombophlebitis	primarily lower limb Deep vein thrombosis abdomen Hepatic veno-occlusive disease Budd–Chiari syndrome May–Thurner syndrome Portal vein thrombosis Renal vein thrombosis upper limb / torso Mondor's disease Paget–Schroetter disease head Cerebral venous sinus thrombosis Post-thrombotic syndrome

Varicose veins	Gastric varices Portacaval anastomosis Caput medusae Esophageal varices Hemorrhoid Varicocele

Other	Chronic venous insufficiency Chronic cerebrospinal venous insufficiency Superior vena cava syndrome Inferior vena cava syndrome Venous ulcer

Arteries or veins

Blood pressure

Hypertension	Hypertensive heart disease Hypertensive emergency Hypertensive nephropathy Essential hypertension Secondary hypertension Renovascular hypertension Benign hypertension Pulmonary hypertension Systolic hypertension White coat hypertension

Hypotension	Orthostatic hypotension

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