Skip to Main Content

Key Features

Essentials of Diagnosis

  • Subarachnoid hemorrhage or focal deficit

  • Abnormal imaging studies

General Considerations

  • Most aneurysms are located

    • On the anterior part of the circle of Willis, particularly on the anterior or posterior communicating arteries

    • At the bifurcation of the middle cerebral artery

    • At the bifurcation of the internal carotid artery

  • Saccular aneurysms ("berry" aneurysms)

    • Occur at arterial bifurcations

    • Are frequently multiple (20% of cases)

    • Are usually asymptomatic

    • May be associated with polycystic kidney disease and coarctation of the aorta

  • Mycotic aneurysms resulting from septic embolism occur in more distal vessels and often at the cortical surface


  • Risk factors for aneurysm formation include smoking, hypertension, and hypercholesterolemia

Clinical Findings

Symptoms and Signs

  • May cause a focal neurologic deficit by compressing adjacent structures

  • Most are asymptomatic or produce only nonspecific symptoms until they rupture, causing a subarachnoid hemorrhage (see Subarachnoid Hemorrhage)

  • "Warning leaks" of a small amount of blood from the aneurysm sometimes precede the major hemorrhage by a few hours or days, leading to headaches, nausea, and neck stiffness

  • Focal neurologic signs may be absent in subarachnoid hemorrhage and secondary to a focal hematoma or ischemia in the territory of the vessel with the ruptured aneurysm

  • Focal arterial spasm in the area of the ruptured aneurysm may occur after 4–14 days, causing hemiplegia or other focal deficits

  • Cause of vasospasm is unknown and likely multifactorial

  • Vasospasm may lead to significant cerebral ischemia or infarction and increase in intracranial pressure

  • Subacute hydrocephalus due to interference with the flow of cerebrospinal fluid may occur after 2 or more weeks; leads to delayed clinical deterioration and is relieved by shunting

Differential Diagnosis

  • Meningitis or meningoencephalitis

  • Ischemic stroke

  • Space-occupying lesion, eg, brain tumor

  • Subdural hemorrhage

  • Epidural hemorrhage

  • Migraine


Imaging Studies

  • Angiography (bilateral carotid and vertebral studies)

    • Definitive evaluation

    • Generally indicates the size and site of the lesion

    • Sometimes reveals multiple aneurysms

    • May show arterial spasm if rupture has occurred

  • Visualization by CT or MR angiography is not usually adequate if operative treatment is under consideration because lesions may be multiple and small lesions are sometimes missed



  • Calcium channel blockers reduce or reverse experimental vasospasm, and nimodipine reduces ischemic deficits from arterial spasm without any side effects (60 mg orally every 4 hours for 21 days)

  • Medical management as outlined for subarachnoid hemorrhage is continued for about 6 weeks and followed by gradual mobilization


  • Definitive treatment requires surgery and clipping of the aneurysm base, or endovascular treatment by interventional radiology

Therapeutic Procedures

  • Major aim is to prevent further hemorrhages

  • Conscious ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.