II. Epidemiology: Incidence
- Incidental finding in 6% of U.S. population
- Family History >1 with aneurysm: 9% of population
III. Risk Factors
-
General risk factors
- Age over 50 years
- More common in women
- Tobacco Abuse
- Cocaine Abuse
- Head Trauma
- Intracranial neoplasm
- Hypertension
- Alcohol use
- Oral Contraceptive
- Hyperlipidemia
- Inherited conditions
- Polycystic Kidney Disease (10-15% have aneurysms)
- Type IV Ehlers-Danlos Syndrome
- Pseudoxanthoma elasticum
- Hereditary Hemorrhagic Telangiectasia
- Neurofibromatosis Type I
- Alpha-1-Antitrypsin Deficiency
- Klinefelter's Syndrome
- Tuberous sclerosis
- Noonan's Syndrome
- Alpha-glucosidase deficiency
- Hypertensive conditions (e.g. Pheochromocytoma)
- No relationship to Marfan's Syndrome
IV. Types
- Saccular Aneurysm (Berry Aneurysm)
- Most common Cerebral Aneurysm (90%)
- Defect in artery tunica muscularis
- Usually occurs at vessel bifurcation
- Fusiform Aneurysm
- Originates in tortuous arteries
- More commonly occurs in vertebrobasilar vessels
- Dissecting Aneurysm
- Result of cystic medial necrosis or Trauma
- Blood follows false lumen
V. Most common sites of aneurysm
VI. Symptoms
- Asymptomatic until rupture in most patients
- See Subarachnoid Hemorrhage
- Headache
- Vision changes or Oculomotor Nerve dysfunction
- Seizures
- Ischemic changes in specific anatomic distribution
VII. Imaging
- Intra-arterial digital subtraction angiography
- Gold Standard
- Permanent neurologic complications in 0.5% cases
- MR angiography
- CT angiography
- Transcranial Doppler Ultrasound
VIII. Complications: Subarachnoid Hemorrhage
- Mortality: 50% for ruptured aneurysm
- Risk of rupture
- Aneurysm >9 mm: 1% annual risk
- Aneurysm <10 mm
- Prior Subarachnoid Hemorrhage: 0.5% annual risk
- No prior Subarachnoid Hemorrhage: 0.05% annual risk
- Recent study suggests 0.1% annual risk if <7 mm
- (2003) Lancet 362:103-10 [PubMed]
IX. Management: Observation
- Periodic imaging with MR Angiogram or CT Angiogram
- Indicated when lesions do not meet criteria for neurosurgery
- Lesion <3 mm
- Lesion 3-7 mm and no high risk criteria (e.g. Posterior Circulation)
- Age over 70 years old
- Approach
- Observed small aneurysms should NOT be considered "time bombs" (rupture risk is low)
- Most patients may participate in regular vigorous Exercise without restriction
X. Management: Neurosurgery
- Indications
- Anterior Circulation aneurysm 7 mm or larger (typically if under age 70 years)
- Posterior Circulation aneurysm 3-7 mm or larger (higher risk of rupture)
- Open repair via craniotomy
- Mortality: 2.6%
- Morbidity: 10.9% (decreased neurologic function)
- Endovascular treatment (Guglielmi detachable coil)
- New procedure with unclear efficacy (ISAT Trial did not evaluate unruptured aneurysm)
- Coiling has become the predominant procedure (based on ISAT Trial)
XI. Prevention
- Screening asymptomatic patients is not recommended
- Screening patients with significant risk factors
- May be indicated in high risk cases
- Example: Two or more family members with aneurysm
- Avoid screening children (delay screening until adult)