An aneurysm is defined as a permanent abnormal dilatation of blood vessel occurring due to congenital or acquired weakening or destruction of the vessel wall. It is a localized sac or dilation formed at a weak point in the wall of the artery. Most commonly, aneurism involves large elastic arteries, especially aorta and its major branches. An aneurysm can cause various ill effects such as thrombosis, alteration in the flow of blood, rupture of vessels and compression of neighbouring structures.
Classification of an Aneurysm
It can be classified on the basis of the various features:
Depending upon the composition of the wall
- A true aneurysm: composed of all layers of normal vessel wall
- A false aneurysm: having fibrous wall and occurring often from trauma to the vessel
Depending upon the shape:
- Saccular: having large spherical outpouching
- Fusiform: having low spindle-shaped dilatation
- Cylindrical: with a continuous parallel dilatation
- Serpentine or varicose: which has tortuous dilation of the vessel
- Racenose or cirocoid: having mass of intercommunicating small arteries and veins
Based on pathogenic mechanisms:
- Atherosclerotic (atherosclerotic) an aneurysm is the most common type
- Syphilitic (luetic) aneurysms found in the tertiary stage of the syphilis
- Dissecting aneurism (dissecting hematoma) in which the blood enters the separated or dissected wall of the vessel.
- Mycotic aneurysms which result from weakening of the arterial wall by microbial infection
- Berry aneurisms which are small dilatation especially affecting the circle of Willis in the base of the brain
Intercerebral or intracranial
- An intracranial (cerebral) aneurism in the dilatation of the walls of a cerebral artery that develops as a result of weakening in the arterial wall. An aneurism may be due to atherosclerosis, which results in a defect in vessel wall with subsequent weakness of the wall; a congenital defect of the vessel wall; hypertensive vascular disease, head trauma or advancing age.
- Any artery within the brain can be the site of a cerebral aneurism, but these lesions usually occur at the bifurcations of the large arteries at the circle of Willis. The cerebral arteries most commonly affected by an aneurysm are the internal carotid artery (ICA), anterior cerebral artery (ACA), anterior communicating artery (ACoA), and posterior communicating artery (PCoA), Middle cerebral artery (MCA).
- Thoracic Aortic Aneurysm: Mostly occurs in hypertensive men between the ages of 40-70 years.
- Ascending Aortic aneurism
- Descending aortic aneurism
- Transverse aortic aneurism
Those aneurism are mostly asymptomatic but the symptoms develop depending upon on how rapidly and in which way the aneurisms surround the thoracic area.
Risk factors for an aneurysm
Clinical features of an aneurysm
Symptoms vary and depend on how rapidly the aneurysm dilates and depends on the different types of an aneurism.
Intracranial (an intercerebral aneurysm)
- Neurological deficits
- Rupture of the aneurism causes sudden, usually severe headache, often loss of consciousness for variable period, pain and rigidity of the back of the neck and spine and visual disturbances (visual loss, diplopia), tinnitus, dizziness and hemiparesis may also occur
- If an aneurism leaks blood and forms a clot, patient may show little neurologic deficit or may have severe bleeding, resulting in cerebral damage followed rapidly by coma and death
Thoracic Aortic Aneurysm
- Constant, boring pain, which may occur only when the patient is in the supine position (prominent symptoms)
- Dyspnea, cough (paroxysmal and brassy)
- Hoarseness, stridor or weakness or aptronia (complete loss of voice)
- Unequal pupils
- Dilated superficial veins on chest, neck and arms
- Some patient is asymptomatic
Abdominal Aortic Aneurysm
- Only about 40% of patient with abdominal aortic aneurysm have symptoms
- Patient complains of “heart beating” in abdomen when lying down or a feeling of an abdominal mass or abdominal throbbing
- Cyanosis and moulting of the toss if aneurism is associated with thrombus
- Sudden onset of severe and persistent pain described as “tearing” or ripping in anterior chest or back extending to shoulders, epigastric area, or abdomen (may be mistaken for acute MI)
- Pallor, sweating and tachycardia
- Blood pressure elevated or markedly different from one arm to another
Diagnosis of an Aneurysm
- History of patient
- Physical examination
- Thoracic Aortic Aneurysm: chest X-ray, CT angiography (CTA), transesophageal echocardiography (TEE)
- Abdominal Aortic Aneurysm: palpation of pulsatile mass in the middle and upper abdomen (a systolic bruit may be heard over the mass), duplex ultrasonography or CTA is used to determine the size, length and location of an aneurism
- Dissecting Aneurysm: arteriography, (TA, TEE, MRI)
- An intracranial aneurysm: MRI, CT-SCAN, Lumbar puncture are diagnostic procedure
Medical or surgical management depends on the type of an aneurysm, for ruptured aneurism, the prognosis is poor and surgery is performed immediately when surgery can be delayed, medical measures are used.
- Strict control of blood pressure
- Systolic pressure maintained at 100 or 120 mmHg with antihypertensive drugs including diuretics, beta-blockers, ACE inhibitors, angiotensin II antagonist and Ca channel blocker
- Allow the brain to recover from the initial insult (bleeding)
- Prevent or minimize the risk of rebleeding
- Prevent or treat other complication; rebleeding, cerebral vasospasm, acute hydrocephalus and seizures
- Provide bed rest with sedation to prevent agitates and stress
- Manage vasospasm with Ca Channel blockers. Endovascular techniques may also be used
- Administer supplemental O2 and maintain Hb and hematocrit at acceptable level to assist in maintaining tissue oxygenation
- Institute surgical treatment (arterial bypass) or medical treatment to prevent rebleeding
- Managed increased ICP and monitor for signs of dehydration and rebound elevation of ICP
- Administer antifibrinolytic agents to delay and prevent dissolution of the clot if surgery is delayed or contraindicated
- Manage systemic hypertension with antihypertensive therapy arterial hemodynamic monitory and stool softeners to prevent straining and elevation of blood pressure
Surgical management of an aneurysm
An expanding or enlarging abdominal aortic aneurism is likely to rupture. Surgery is the treatment of choice for abdominal aortic aneurysm more than 5.5 cm (2inc) wide or those are enlarging; the standard treatment has been open surgical repair of an aneurism by resecting the vessel and sewing a bypass graft in peace. An alternative for treating a comparable abdominal aortic aneurysm is endovascular grafting, which involves the transluminal placement and attachment of a sutureless aortic graft prosthesis occur aneurysms.