Aneurysm, Intracranial

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

  • Are associated with polycystic kidney disease, moyamoya disease, familial aldosteronism type 1, and coarctation of the aorta

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

Demographics

• Risk factors for aneurysm formation include cigarette smoking, hypertension, and female sex

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 a 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

• Digital subtraction 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

  • Not usually adequate if operative treatment is under consideration because lesions may be multiple and small lesions are sometimes missed

  • Can be used to screen patients who have two or more first-degree relatives with intracranial aneurysms

Medications

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

Surgery

• 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 patients are

  • Confined to bed

  • Advised against exertion or straining

  • Treated symptomatically for headache and anxiety

  • Given laxatives or stool softeners

• If severe hypertension, lower blood pressure gradually but not below a diastolic level of 100 mm Hg

Follow-Up

• After surgical obliteration of aneurysms, symptomatic vasospasm may be treated by

  • Intravascular volume expansion

  • Induced hypertension

  • Transluminal balloon angioplasty of involved intracranial vessels

Complication

• Subarachnoid hemorrhage; factors that confer a higher risk for this complication include

  • Older age

  • Female sex

  • "Non-white" ethnicity

  • Hypertension

  • Tobacco smoking

  • High alcohol consumption (exceeding 150 g per week)

  • Previous symptoms

  • Posterior circulation aneurysms

  • Larger aneurysms

Prognosis

• Unruptured aneurysms that are symptomatic merit prompt treatment

• However, small asymptomatic aneurysms discovered incidentally are often monitored arteriographically and corrected surgically only if > 10 mm

• Greatest risk of further hemorrhage is within a few days of initial bleed; thus, early obliteration (within 2 days) is preferred

• Approximately 20% of patients will have further bleeding within 2 weeks and 40% within 6 months

When to Refer

• All patients should be referred

When to Admit

• All patients with a subarachnoid hemorrhage

• All patients for detailed imaging

• All patients undergoing surgical or endovascular treatment