Cerebral Aneurysm

Aka: Cerebral Aneurysm, Intracranial Aneurysm, Berry Aneurysm

1. See Also
   1. Neurovascular Anatomy
   2. Subarachnoid Hemorrhage
2. Epidemiology: Incidence
   1. Incidental finding in 6% of U.S. population
   2. Family History >1 with aneurysm: 9% of population
3. Risk Factors
   1. General risk factors
      1. Age over 50 years
      2. More common in women
      3. Tobacco abuse
      4. Cocaine abuse
      5. Head Trauma
      6. Intracranial neoplasm
      7. Hypertension
      8. Alcohol use
      9. Oral Contraceptive
      10. Hyperlipidemia
   2. Inherited conditions
      1. Polycystic Kidney Disease (10-15% have aneurysms)
      2. Type IV Ehlers-Danlos Syndrome
      3. Pseudoxanthoma elasticum
      4. Hereditary Hemorrhagic Telangiectasia
      5. Neurofibromatosis Type I
      6. Alpha-1-Antitrypsin Deficiency
      7. Klinefelter's Syndrome
      8. Tuberous sclerosis
      9. Noonan's Syndrome
      10. Alpha-glucosidase deficiency
      11. Hypertensive conditions (e.g. Pheochromocytoma)
      12. No relationship to Marfan's Syndrome
4. Types
   1. Saccular Aneurysm (Berry Aneurysm)
      1. Most common Cerebral Aneurysm (90%)
      2. Defect in artery tunica muscularis
      3. Usually occurs at vessel bifurcation
   2. Fusiform Aneurysm
      1. Originates in tortuous arteries
      2. More commonly occurs in vertebrobasilar vessels
   3. Dissecting Aneurysm
      1. Result of cystic medial necrosis or trauma
      2. Blood follows false lumen
5. Most common sites of aneurysm
   1. Anterior Communicating Artery (35%)
   2. Posterior Communicating Artery (35%)
   3. Middle Cerebral Artery (20%)
6. Symptoms
   1. Asymptomatic until rupture in most patients
   2. See Subarachnoid Hemorrhage
   3. Headache
   4. Vision changes or Oculomotor Nerve dysfunction
   5. Seizures
   6. Ischemic changes in specific anatomic distribution
      1. Anterior Cerebral Artery CVA
      2. Middle Cerebral Artery CVA
      3. Vertebro-Basilar CVA
      4. Posterior Cerebral Artery CVA
      5. Posterior Inferior Cerebellar Artery CVA
7. Radiology
   1. Intra-arterial digital subtraction angiography
      1. Gold Standard
      2. Permanent neurologic complications in 0.5% cases
   2. MR angiography
   3. CT angiography
   4. Transcranial Doppler ultrasound
8. Complications: Subarachnoid Hemorrhage
   1. Mortality: 50% for ruptured aneurysm
   2. Risk of rupture
      1. Aneurysm >9 mm: 1% annual risk
      2. Aneurysm <10 mm
         1. Prior Subarachnoid Hemorrhage: 0.5% annual risk
         2. No prior Subarachnoid Hemorrhage: 0.05% annual risk
            1. Recent study suggests 0.1% annual risk if <7 mm
            2. (2003) Lancet 362:103-10
9. Management: Observation
   1. Indicated when lesions do not meet criteria for neurosurgery
   2. Observed small aneurysms should not be considered "time bombs" (rupture risk is low)
   3. Most patients may participate in regular vigorous Exercise without restriction
10. Management: Neurosurgery
    1. Indications
       1. Anterior circulation aneurysm 7 mm or larger
       2. Posterior circulation aneurysm 3-7 mm or larger (higher risk of rupture)
    2. Open repair via craniotomy
       1. Mortality: 2.6%
       2. Morbidity: 10.9% (decreased neurologic function)
    3. Endovascular treatment (Guglielmi detachable coil)
       1. New procedure with unclear efficacy (ISAT Trial did not evaluate unruptured aneurysm)
       2. Coiling has become the predominant procedure (based on ISAT Trial)
11. Prevention
    1. Screening asymptomatic patients is not recommended
    2. Screening patients with significant risk factors
       1. May be indicated in high risk cases
       2. Example: Two or more family members with aneurysm
       3. Avoid screening children (delay screening until adult)
12. References
    1. (1998) N Engl J Med 339:1725-33
    2. Raaymakers (1998) Stroke 29:1531-8
    3. Vega (2002) Am Fam Physician 66(4):601-8
    4. Wardlaw (2000) Brain 123:205-21