What Is An Aneurysm? What Causes Aneurysm?

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Main Category: Cardiovascular / Cardiology
Also Included In: Vascular
Article Date: 09 Jul 2009 - 9:00 PDT

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An aneurysm occurs when part of a blood vessel (artery) or cardiac chamber swells, - either the blood vessel is damaged or there is a weakness in the wall of the blood vessel. As blood pressure builds up it balloons out at its weakest point. The swelling can be quite small or very large - when large it tends to extend along the blood vessel. As the aneurysm grows there is a greater risk of rupture - this can lead to severe hemorrhage, and other complications, including sudden death.

According to Medilexicon's medical dictionary, an aneurysm is a "Circumscribed dilation of an artery or a cardiac chamber, in direct communication with the lumen, usually resulting from an acquired or congenital weakness of the wall of the artery or chamber."

An aneurysm can occur in any part of the body. They tend to most commonly occur on the wall of the aorta - the large trunk artery that carries blood from the left ventricle of the heart to branch arteries. The aorta goes down through the chest and into the abdomen, where it divides into the iliac arteries (two branches). There are two main types of aneurysms:

• Aortic aneurysm - occurs in the aorta. Can be abdominal, or thoracic (higher up).


• Cerebral aneurysm - occurs in an artery in the brain.

People of any age and either sex can have an aneurysm, although they are more common in men and people over 65 years of age.

What are the symptoms of an aneurysm?

Symptoms are linked to how big the aneurysm is, how fast it is growing and its location. Very small aneurysms which do not grow may go completely unnoticed. A large cerebral aneurysm (in the brain) may press on nerve tissue and trigger numbness in the face, or problems with the eyes.

Cerebral (brain) aneurysm symptoms

The following symptoms may be experienced before a cerebral aneurysm ruptures:

• Very severe headache that occurs suddenly
• Nausea
• Vomiting
• Eyesight problems
• Seizures (fits)
• Loss of consciousness
• Confusion
• A drooping eyelid
• Stiff neck
• Light sensitivity

If the cerebral aneurism bursts it will cause bleeding in the brain and a hemorrhagic stroke - it can also cause intracranial hematoma (blood leaks into the area surrounding the brain causing a blood clot in the skull).

Aortic aneurysm symptoms

The vast majority of aortic aneurysms occur in the patient's abdominal aorta. It is not uncommon for a patient to have an aneurysm and experience no symptoms for several years. Many of them are difficult to detect because of this. Some aortic aneurysms will never rupture. It is hard to predict which ones will never grow, which grow slowly, and which ones grow rapidly.

When symptoms occur, they tend to include:

• A throbbing sensation in the abdomen
• Back pain
• Abdominal pain - this pain frequently spreads towards the back
If the aneurysm continues to grow and presses on the spine or chest organs the patient may experience:
• Coughing
• Loss of voice
• Breathing difficulties
• Problems swallowing

Sometimes an aortic aneurysm can be discovered by a GP (general practitioner, primary care physician) when performing a routine examination of the abdomen. He/she may detect a lump that pulses at the same rate as the patient's heartbeat - it is often located high up in the abdomen, slightly to the right.

What causes an aneurysm?

Brain (cerebral) aneurysm causes:

• Weakness in the artery wall (usually present since birth)
• Hypertension (high blood pressure)
• Arteriosclerosis (plaques of cholesterol, platelets, fibrin, and other substance form on the arterial wall)

Most cerebral aneurysms develop at the forks or branches in arteries because the walls in these sections are weaker. They most commonly form at the base of the brain - but can form anywhere in the brain.

Abdominal aortic aneurysm causes:

• Atherosclerosis - accumulation of fatty deposits (cholesterol) on the artery walls.


• Smoking - this is a major risk factor in the development of aortic aneurisms. Smoking contributes to atherosclerosis, hypertension and the acceleration of aneurysm growth. Compared to women who have quit smoking, women smokers are four times more likely to have an abdominal aortic aneurysm repair or ruptura, according to researchers at the VA Medical Center, Minneapolis.


• Hypertension - especially if it is poorly controlled (not treated at all, or not treated properly).


• Vasculitis (infection in the aorta) - this is an uncommon cause, and seems to run in families.


• Cocaine use - Cocaine users in their mid-40s had more than four times the risk of coronary artery aneurysms as non-users, according to a study at Minneapolis Heart Institute Foundation at Abbott Northwestern Hospital.

Thoracic aortic aneurysm causes:

About 1 in 4 aortic aneurysms occur in the thoracic area of the aorta (higher up in the chest). Causes are the same as with aortic aneurysms, plus the following below:

• Marfan syndrome - this is a genetic disorder of the connective tissue; it is a much less common cause of aortic aneurysm.


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• Previous aorta injury - people with a previous injury to the aorta, such as aortic dissection (tear in the wall of the aorta) have a higher risk of developing a thoracic aortic aneurysm.


• Traumatic injury - this could be cause by a vehicle accident or a bad fall.

How is an aneurysm diagnosed?

Aortic aneurism diagnosis:

The majority of abdominal aortic aneurysms are discovered when doctors are examining a patient for some other reason, such as during a chest X-ray or ultrasound, according to this report by The Mayo Clinic. If an aortic aneurysm is suspected some specific tests will be ordered, they include:

• Abdominal ultrasound - the patients lie on their back and some warm gel is applied to the skin of their abdomen prior to the examination. The gel reduces the chances of air pockets forming on the surface of the skin when the device (transducer) is placed on it. The transducer is moved along the surface of the abdominal skin and sends images to a monitor - from this monitor it is possible for a trained technician to detect a potential aneurysm.


• CT (computerized tomography) scan - X-rays are used to create a 3-dimensional picture of the target area.


• MRI (magnetic resonance imaging) scan - magnets and radio waves produce 2-dimensional and 3-dimensional pictures of the target area.


• Regular screening for those at risk - as many aneurysms present no symptoms, people aged 60 or over and who are deemed to be at risk of developing an aortic aneurysm are advised to undergo regular screening. These may include men over 65 who have smoked regularly (even if they have given up), as well as men with a family history of abdominal aortic aneurysm. This report concluded that "The National Aortic Screening Programme" in the UK should, in due course, prevent about half of all aneurysm deaths in men over 65 and will be extremely cost effective for the NHS.

Cerebral aneurysm diagnosis:

Patients who suddenly have a very severe headache, or other symptoms which may indicate a ruptured cerebral aneurysm will most likely undergo some tests to find out whether there is any subarachnoid hemorrhage or some other type of stroke. If bleeding is detected, the emergency care team will determine whether an aneurysm was the cause. Patients who do not have a ruptured cerebral aneurysm, but have symptoms such as pain behind the eye, changes in vision, or paralysis on one side of their face, will also undergo tests. These tests may include:

• A CT (computerized tomography) scan - X-rays are used to create a 3-dimensional picture of the target area. Multidetector computed tomography (MDCT) angiography is highly accurate in depicting intracranial aneurysms, according to a study carried out by researchers at the Department of Radiology at Klinikum Duisburg in Germany.


• A cerebrospinal fluid test - anyone who had a subarachnoid hemorrhage will probably have red blood cells in the cerebrospinal fluid (the fluid surrounding the brain and spine). Patients who have symptoms of a ruptured aneurysm but had a CT scan which did not show any evidence of bleeding will undergo this cerebrospinal fluid test; called a lumbar puncture or spinal tap.


• MRI (magnetic resonance imaging) scan - this test is better than a CT scan at detecting a ruptured aneurysm.


• Cerebral arteriogram (cerebral angiogram) - a catheter is inserted into a large artery, usually entering the patient in his/her groin, and threads past the heart to the brain arteries. A special dye goes into the arteries via the catheter which shows up in X-ray images - the doctor can then see details about the conditions of the arteries and the site of a ruptured aneurysm. As this quite an invasive procedure, it is only generally used when other procedures have not provided enough data.

Treatment for an aneurysm

Aortic aneurysm treatment:

The aim is to prevent the aneurysm from bursting. There are usually two choices - 1. Watch and wait. 2. Surgery. How big the aneurysm is, how fast it's growing, and sometimes its location are vital factors in determining what treatment to use.

• If the aneurysm is small - if the patient's aneurysm is no bigger than 1.6 inches (about 4cm) in diameter, and there are no symptoms, it may be best to tack the approach of watching-and-waiting, instead of surgery. This is also known as "watchful waiting". In most cases the risks caused by surgery are greater than the likely risks caused by a small aneurysm. Watchful waiting usually involves an ultrasound scan every 6 to 12 months. The patient will be asked to be alert for any signs or symptoms of dissection or rupture.
  
  Small observational studies have suggested that statins can significantly reduce the growth rate of small abdominal aortic aneurysms, Janet T. Powell, M.D., Ph.D., Professor at Imperial College and Honorary Consultant for United Healthcare in London revealed.


• If the aneurysm is medium-sized - a medium-sized aneurysm is no bigger than 2.2 inches (5.5 cm) in diameter and bigger than 1.6 inches (4 cm). It is more difficult now to weigh up the risks of surgery against the risks of a medium-sized aneurysm. The chances of both patient and doctor deciding on one or the other are pretty even.


• Large-sized or rapidly-growing aneurysm - a large aneurysm is larger than 2.2 inches (5.5 cm) in diameter, while a rapidly growing one is expanding at more than 0.5 cm every six months. In most cases the patient will require surgery. The damaged section of the aorta will be removed and replaced with a graft (synthetic tube) which is sewn into place. This is major surgery - open-abdominal or open-chest surgery. The patient will take several months to recover completely.
  
  Endovascular surgery - this is a less invasive procedure to repair an aneurysm. A graft is attached to the end of the catheter which is inserted through an artery and threaded up into the aorta. The graft - consisting of a woven tube covered by a metal mesh support - is placed at the site of the aneurysm and stuck there will pins or small hooks. This graft strengthens the weakened section of the aorta and prevents the aneurysm from rupturing. Patients recover much faster with this procedure, and seem to have fewer complications.
  
  Long-term survival for patients undergoing surgical repair of intact abdominal aortic aneurysms has improved in recent decades, according to a Swedish study.

Thoracic aortic aneurysm treatment:

Surgery is usually required as soon as the aneurysm reaches a diameter of 2.2 inches (5.5 cm). Patients with Marfan syndrome, as well as those with close relative who had an aortic dissection may undergo surgery if the aneurysm is smaller. Beta blockers have been shown to slow down the growth of thoracic aortic aneurysms for patients with Marfan syndrome.

Cerebral (brain) aneurysm treatment:

Ruptured cerebral aneurysm treatment

Patients with brain aneurysms have two options if the aneurysm has ruptured: 1. Surgical clipping. 2. Endovascular coiling.

• Surgical clipping - the aneurysm is closed off. The surgeon removes a section of the skull to get to the aneurysm and finds the blood vessel that feeds it. A tiny metal clip is placed on the neck of the aneurysm to block off the blood flow to it.


• Endovascular coiling - a catheter is inserted, usually in the groin, and is threaded through the body to the brain where the aneurysm is located. A guide wire is used to push a soft platinum wire through the catheter and into the aneurysm. The wire coils up inside the aneurysm and disrupts the blood flow, making it clot. The clotting of the blood effectively seals off the aneurysm from the artery.


• Endovascular, noninvasive thoracic aortic aneurysm repair (TEVAR) is safer than open aneurysm repair (OAR) as it is associated with fewer cardiac, respiratory, and hemorrhagic complications, as well as a shorter hospital stay, this study revealed.
  
  Patients whose aneurysms are coiled instead of clipped have a better survival rate over five years, according to a long-term study of the International Subarachnoid Aneurysm Trial (ISAT). However, another study found that over time outcomes are similar.
  
  Smokers who undergo coil embolization are at a high risk of having another aneurism elsewhere later on, this study revealed .

The following cerebral aneurysm treatments help relieve symptoms as well as managing complications:

• Painkillers - usually for headaches.


• Calcium channel blockers - these stop calcium for entering cells of the blood vessel walls. They reduce the amount of widening and narrowing of blood vessels; often a complication of a ruptured aneurysm.


• A vassopressor - this is an injected drug which raises blood pressure; widens blood vessels which have remained stubbornly narrowed. The aim is to prevent stroke.


• Anti-seizure drugs - seizures may occur after an aneurysm has ruptures. Examples include levetiracetam (Keppra), phenytoin (Dilantin, Phenytek, others) and valproic acid (Depakene).


• A ventricular catheter - this can reduce the pressure on the brain caused by hydrocephalus (excess cerebrospinal fluid). The catheter, which is placed in the spaces filled with fluid inside the brain, drains the excess liquid into an external bag. It may be necessary to place a shunt system - a shunt (flexible silicone rubber tube) and a valve. The shunt system is a drainage channel that starts in the brain and ends in the patient's abdominal cavity.


• Rehabilitation therapy - sometimes a subarachnoid hemorrhage causes brain damage, resulting in impaired speech and bodily movements. Rehabilitation therapy helps the patient relearn vital skills.

Unruptured cerebral aneurysm treatment

The unruptured cerebral aneurysm can be sealed off with surgical clipping or endovascular coiling. Deciding on this is not easy as the risks are often equal, and sometimes higher than the potential benefits. The following will help the surgeon determine what to do:

• Exactly where the aneurysm is.
• How big the aneurysm is.
• The patient's age.
• The patient's general state of health
• Whether the patient has a family history of ruptured aneurysms.
• Whether the patient has any congenital conditions which may raise the risk of the aneurysm rupturing.

Patients with hypertension (high blood pressure) need to have their condition carefully monitored - proper control of hypertension significantly reduces the likelihood of a rupture.

Complications

A ruptured aneurysm is a major problem. An abdominal aneurysm rupture will cause mass bleeding leading to shock, and even death.

A cerebral aneurysm rupture causes serious bleeding into the fluid surrounding the brain. The patient will have an extremely painful headache, which is usually followed by loss of consciousness. A cerebral aneurysm rupture is a life threatening emergency.

Occasionally, a piece from inside an aneurysm may become dislodged and travel into the artery - the clot is known as a thrombosis. If it lodges into a small artery it will block blood flow. The blocked blood flow can be very serious, especially if it happens in an artery to a major organ, such as the heart, lungs or brain.

Prevention

A large percentage of aneurysms are caused by arteriosclerosis - a vascular disease. The following steps will help prevent the development of arteriosclerosis and aneurysms:

• Quit smoking
• Keep your blood pressure under control
• Keep your blood cholesterol levels under control
• Eat a healthy, well balanced diet, rich in fruit and vegetables, unrefined carbohydrates, dietary fiber, good quality fats, and lean protein
• Keep your bodyweight within the ideal limits for your height
• Get at least 7 hours of good quality sleep each night
• Keep yourself physically active (check with your doctor that this is OK for you)

Written by Christian Nordqvist


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