Aneurysm is an abnormal dilation (ballooning) of an artery caused by the pressure of blood flowing through a weakened area. The weakening may be due to disease, injury, or a congenital (present from birth) defect of the arterial wall. Aneurysm most commonly affect the aorta and arteries supplying the brain.

ANEURYSM TYPES AND CAUSES

The most common cause of an aneurysm is atherosclerosis, a condition in which fatty deposits weaken the artery wall. The aorta is the usual site of atherosclerotic aneurysm.

Less commonly, aneurysm may be due to a congenital (present from birth) weakness of the artery walls. Most cerebral aneurysm, known as berry aneurysm because of their appearance, are congenital. Marfan syndrome, an inherited disorder in which the wall of the aorta is defective, is often associated with aneurysm just above the heart. The arterial wall can also be weakened by inflammation, as occurs in polyarteritis nodosa. A dissecting aneurysm is one in which the inner layer of the artery wall ruptures, allowing blood to track along the length of the artery and block any branching arteries. Ventricular aneurysms are aneurysms that sometimes develop in the heart wall due to weakening of the area of heart muscle as a result of a heart attack (myocardial infarction).

Some of the common types, sites, and shapes of aneurysm are shown in the box.

TYPES OF ANEURYSM

An aneurysm forms when pressure from the blood flow causes a weakened artery wall to distend or forces blood through a fissure. Aneurysm can form anywhere in the body, although the most common sites are the aorta and the arteries supplying the brain.

Common aneurysm

This type forms when the tunica media, the artery’s middle wall, is weakened; the strong force of the blood flow distends the wall of the artery.

Dissecting aneurysm

In this type, blood is forced through a fissure in the internal wall of the artery. The internal lining is stripped away, forming a false channel.

Cerebral (or berry) aneurysm

A swelling where arteries branch, often at the base of the brain, usually caused by congenital weakness.

Saccular aneurysm

A balloon-shaped distension of part of the wall of an artery, often seen in aortic aneurysm just above the heart.

Fusiform aneurysm

A spindle-shaped distension around the circumference of an artery. often seen in lower aortic aneurysms.

ANEURYSM SYMPTOMS AND SIGNS

Most aneurysms are symptomless ad remain undetected. However, if the aneurysm expands rapidly and causes pain, or is very large, the symptoms are due to pressure on nearby structures. Aneurysms can eventually rupture, cause fatal blood loss or, in the case of a cerebral aneurysm, loss of consciousness. A dissecting aneurysm usually causes severe pain,  and there is a high risk of a vessel rupturing. Ventricular aneurysms seldom rupture, but they interfere with the pumping action of the heart.

ANEURYSM DIAGNOSIS AND TREATMENT

Aneurysms of the aorta may be detected by ultrasound scanning, and cerebral aneurysm by CT scanning or MRI. Angiography can provide more detailed information on all types of aneurysm. A ruptured or enlarged aneurysm requires immediate arterial reconstructive surgery.

Source: A-Z family medical encyclopedia by BMA

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