Aneurysm

True aneurysms are an abnormal dilation of an artery due to a weakened vessel wall. By contrast, false aneurysms are external hematomas with a persistent communication to a leaking artery. Dissections are a separation of the arterial wall layers caused by blood entering the intima-media space after a tear in the internal layer occurred. Aneurysms are differentiated according to their location. This card discusses the etiology and clinical features of cerebral, external carotid, Iliofemoral, popliteal, and ventricular aneurysms. Symptoms generally depend on the location and size of the aneurysm. There are surgical and endovascular treatment options, the choice of which depends on the specific type of aneurysm and if symptoms or complications are present.

For more specific information on individual types of aneurysms, see the articles on thoracic aortic aneurysm, abdominal aortic aneurysm, aortic dissection, dissection of the carotid and the vertebral artery, and subarachnoid hemorrhage.

Types

• Berry aneurysms
  • Most common type of cerebral aneurysms
  • Have a round, saccular shape
  • Typically occur at the junctions of vessels in the circle of Willis (the most commonly involved junction is between the anterior communicating artery and anterior cerebral artery)
  • Account for approx. 80% of cases of nontraumatic subarachnoid hemorrhage
  • Risk factors ^[5][6]
    • History of congenital conditions: autosomal-dominant polycystic kidney disease, Ehlers-Danlos syndrome, Marfan syndrome, aortic coarctation
    • Hypertension
    • Smoking
    • African-American race
    • Advanced age
    • Hyperlipidemia
    • Excessive alcohol consumption
    • Family history of aneurysms
    • Estrogen deficiency
• Fusiform aneurysms ^[7]
  • Dilation of the entire circumference of the artery
  • Most frequently occur in the vertebrobasilar system
  • Associated with connective tissue diseases and atherosclerosis
• Mycotic aneurysms ^[8]
  • Mushroom-shaped dilations of infected vessel walls
  • Caused by septic emboli (mostly due to bacterial endocarditis)
  • Occur at small, peripheral segments of cerebral vessels and often involve the middle cerebral artery. ^[9]
• Traumatic aneurysms ^[10]
  • Comprise < 1% of all intracranial aneurysms
  • Most commonly occur in the supraclinoid ICA and the anterior cerebral artery
  • Have a high risk of rupture
• Charcot-Bouchard microaneurysms
  • Associated with hypertension and diabetes.
  • Affect small lenticulostriate vessels in the basal ganglia and thalamus.
  • Their rupture is the most common cause of intracerebral hemorrhage.

Clinical features

• Usually asymptomatic
• The mass effect of the saccular aneurysms depends on the affected vessel.
  • Anterior communicating artery: bitemporal hemianopia; visual acuity defects; (CN II compression at the optic chiasm)
  • Posterior communicating artery: mydriasis (CN III parasympathetic fibers compression); ptosis and ophthalmoplegia in severe compression
• See clinical features of ruptured cerebral aneurysms in the “Clinical features” section in the article on “Subarachnoid hemorrhage.”

Diagnosis

• Angiography: determines location, size, and morphology of aneurysm (with the exception of Charcot-Bouchard aneurysms, which cannot be detected on angiography)
• See “Subarachnoid hemorrhage” for workup of suspected aneurysmal subarachnoid hemorrhage.

Treatment

• Unruptured intracranial aneurysms ^[11]
  • Conservative management includes maintaining normal blood pressure, cessation of smoking, and imaging follow-up.
  • Surgical clipping or endovascular coiling can be considered for patients with life expectancy of > 10 years in the following cases:
    • Large (> 5 mm) or increasing during follow-up aneurysm
    • Location in the posterior circulation or communicating arteries
    • History of subarachnoid hemorrhage
• Ruptured aneurysms: See “Subarachnoid hemorrhage.”

• Etiology: commonly atherosclerosis, trauma (iatrogenic or penetrating injury), infection (septic emboli)
• Clinical features
  • Pulsatile neck mass (below angle of mandible)
  • Associated bruit
  • Transient ischemic attacks (TIAs) or stroke
  • Mass effect on adjacent structures (veins and nerves) causes hoarseness, facial swelling, dysphagia
• Diagnosis
  • Ultrasound (initial): evidence of swirling blood with a thrombus
  • CT or MR angiography: determines the site and size of the aneurysm, excludes rupture or other pathologies
• Complications
  • Rupture: airway compression, pharyngeal hemorrhage, epistaxis
  • Neck infection: pain, fever
• Treatment: surgical repair, either in the form of an aneurysm excision and reconstruction or endovascular repair (grafting or stenting) ^[12]

• Etiology
  • Myocardial infarction; (occurs in 8–15% of patients; 2 weeks to months after MI)
  • Risk factors ^[13]
    • Complete occlusion of the left anterior descending coronary artery
    • Female sex
• Location: ∼ 85% in the anterior or apical walls, 10–15% in the inferior-basal walls of the left ventricle
• Clinical features
  • Enlarged heart on percussion
  • Diffuse and displaced apical pulse to left midclavicular line
  • 3^rd and 4^thheart sounds
  • Systolic murmur (mitral regurgitation)
• Diagnosis
  • ECG: persistent ST elevation
  • Echocardiography (or CT or MRI ; ): dyskinetic wall motion and diastolic deformity
• Complications
  • Arrhythmias
  • Ventricular rupture → cardiac tamponade
  • Thrombus formation → thromboembolism (stroke, mesenteric ischemia, renal infarction)
  • Heart failure
• Treatment ^[14]
  • Small and asymptomatic: conservative treatment with regular follow-up
  • If large, symptomatic, or there is evidence of a thrombus
    • ACE inhibitors
    • Anticoagulation
  • If not responsive to medical therapy: surgical resection of the aneurysm

• Epidemiology
  • Prevalence: most common peripheral aneurysm and second most common aneurysm after AAAs
  • ♂ > ♀
  • Mean age: 65 years
• Etiology: multifactorial (i.e., inflammation, immune, genetic, and mechanical factors)
• Clinical features
  • Usually asymptomatic mass in the popliteal fossa (50% are bilateral)
  • If symptomatic
    • Knee pain
    • Acute limb ischemia → 6 Ps
    • Chronic limb ischemia
• Diagnosis
  • Doppler ultrasonography (best initial): excludes Baker's cyst; identifies thrombus and patency of vessel
  • CT angiography: preoperative assessment
• Complications
  • Rupture
  • Distal embolization: blue toe syndrome (small vessel occlusion caused by an embolus)
  • Chronic thrombosis
• Treatment
  • Anticoagulation (e.g., heparin) ^[15]
  • Surgery with venous bypass graft or surgical aneurysmal excision
    • Indication: symptomatic or ≥ 2 cm in diameter

References:^[16][17]

• Epidemiology: Second most common peripheral aneurysm after popliteal aneurysms
• Etiology: See “Risk factors for atherosclerosis.”
• Clinical features
  • May be asymptomatic
  • Acute limb ischemia → 6 Ps
  • Compression of nearby nerves or veins: sudden pain, weakness, swelling, numbness in the leg
  • Painless, pulsatile swelling with a palpable thrill at the mid-inguinal point
  • Auscultation of the swelling: loud, harsh, continuous murmur
  • Often associated with other aneurysms, esp. AAA and thoracic aortic aneurysm
• Diagnosis
  • Doppler ultrasonography (best initial test): identifies thrombus and patency of vessel
  • CT angiography: preoperative assessment
• Complications
  • Rupture: acute groin pain
  • Blue toe syndrome
• Treatment
  • Procedure: surgery with bypass or surgical excision of aneurysm
  • Indication
    • Symptomatic
    • IAA ≥ 3 cm
    • Rapidly expanding
    • Coexistent AAA
    • Complications are present

References:^[18][19][20]