Brain aneurysm

Definition:
Brain aneurysm is a cerebrovascular disorder in which weakness in the wall of a cerebral artery or vein causes a localized dilation or ballooning of the blood vessel.Brain aneurysms are like tiny blisters or balloons on the surface of the arteries running through the brain. The outer wall of the vessel has a weakness, and the inner lining (like the inner tube of a tyre) bulges out. In 15 per cent of cases there are multiple aneurysms on different arteries around the brain.

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A common location of brain aneurysms is on the arteries at the base of the brain, known as the Circle of Willis. Approximately 85% of cerebral aneurysms develop in the anterior part of the Circle of Willis, and involve the internal carotid arteries and their major branches that supply the anterior and middle sections of the brain. The most common sites include the anterior cerebral artery and anterior communicating artery (30-35%), the bifurcation, division of two branches, of the internal carotid and posterior communicating artery (30-35%), the bifurcation of the middle cerebral artery (20%), the bifurcation of the basilar artery, and the remaining posterior circulation arteries (5%).

The main worry with an aneurysm is that it will burst under the pressure of blood pulsing through the artery, causing a brain haemorrhage, which may be fatal.

Each year, many thousands of people around the world, often young or middle-aged, die or are left disabled because of brain aneurysms.

Symptoms:
Most brain aneurysms cause no symptoms and may only be discovered during tests for another, usually unrelated, condition. In other cases, an unruptured aneurysm will cause problems by pressing on areas within the brain. When this happens, the person may suffer from severe headaches, blurred vision, changes in speech, and neck pain, depending on the areas of the brain that are affected and the severity of the aneurysm.

Onset is usually sudden and without warning. Rupture of a cerebral aneurysm is dangerous and usually results in bleeding into the meninges or the brain itself, leading to a subarachnoid hemorrhage (SAH) or intracranial hematoma (ICH), either of which constitutes a stroke. Rebleeding, hydrocephalus (the excessive accumulation of cerebrospinal fluid), vasospasm (spasm, or narrowing, of the blood vessels), or multiple aneurysms may also occur. The risk of rupture from an unruptured cerebral aneurysm varies according to the size of an aneurysm, with the risk rising as the aneurysm size increases. The overall rate of aneurysm rupture is estimated at 1.3% per year, resulting in approximately 27,000 new cases of SAH in the United States per year. Screening for aneurysms with annual imaging is possible, but not viewed as cost effective. The risk of short term re-rupture decreases dramatically after an aneurysm has bled in about 3 days, though after approximately 6 weeks the risk returns to baseline.

Symptoms of a ruptured brain aneurysm often when come on suddenly. They may include:

*Sudden, severe headache (sometimes described as a “thunderclap” headache that is very different from any normal headache).
*Neck pain.
*Nausea and vomiting.
*Sensitivity to light.
*Fainting or loss of consciousness.
*Seizures.

If a brain aneurysm presses on nerves in your brain, it can cause signs and symptoms. These can include:

*A droopy eyelid
*Double vision or other changes in vision
*Pain above or behind the eye
*A dilated pupil
*Numbness or weakness on one side of the face or body

Causes:
Aneurysms may result from congenital defects, preexisting conditions such as high blood pressure and atherosclerosis (the buildup of fatty deposits in the arteries), or head trauma. Cerebral aneurysms occur more commonly in adults than in children but they may occur at any age.

A person may inherit the tendency to form aneurysms, or aneurysms may develop because of hardening of the arteries (atherosclerosis) and aging. Some risk factors that can lead to brain aneurysms can be controlled, and others can’t. The following risk factors may increase your risk of developing an aneurysm or, if you already have an aneurysm, may increase your risk of it rupturing:1

*Family history. People who have a family history of brain aneurysms are twice as likely to have an aneurysm as those who don’t.

*Previous aneurysm. About 20% of patients with brain aneurysms have more than one.

*Gender. Women are twice as likely to develop a brain aneurysm or to suffer a subarachnoid hemorrhage as men.

*Race. African Americans have twice as many subarachnoid hemorrhages as whites.

*Hypertension. The risk of subarachnoid hemorrhage is greater in people with a history of high blood pressure (hypertension).

*Smoking. In addition to being a cause of hypertension, the use of cigarettes may greatly increase the chances of a brain aneurysm rupturing.

Diagnosis:
Because unruptured brain aneurysms often do not cause any symptoms, many are discovered in people who are being treated for a different condition.

 

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These images show exactly how blood flows into the brain arteries.

If your health professional believes you have a brain aneurysm, you may have the following tests:

*Computed tomography (CT) scan. A CT scan can help identify bleeding in the brain.

*Computed tomography angiogram (CTA) scan. CTA is a more precise method of evaluating blood vessels than a standard CT scan. CTA uses a combination of CT scanning, special computer techniques, and contrast material (dye) injected into the blood to produce images of blood vessels.

*Magnetic resonance angiography (MRA). Similar to a CTA, MRA uses a magnetic field and pulses of radio wave energy to provide pictures of blood vessels inside the body. As with CTA and cerebral angiography, a dye is often used during MRA to make blood vessels show up more clearly.

*Cerebral angiogram. During this X-ray test, a catheter is inserted through a blood vessel in the groin or arm and moved up through the vessel into the brain. A dye is then injected into the cerebral artery. As with the above tests, the dye allows any problems in the artery, including aneurysms, to be seen on the X-ray. Although this test is more invasive and carries more risk than the above tests, it is the best way to locate small (less than 5 mm) brain aneurysms.

Sometimes a lumbar puncture may be used if your health professional suspects that you have a ruptured cerebral aneurysm with a subarachnoid hemorrhage.

Treatment:
Emergency treatment for individuals with a ruptured cerebral aneurysm generally includes restoring deteriorating respiration and reducing intracranial pressure. Currently there are three treatment options for brain aneurysms: medical hypotensive therapy; surgical clipping or endovascular coiling. If possible, either surgical clipping or endovascular coiling is usually performed within the first 24 hours after bleeding to occlude the ruptured aneurysm and reduce the risk of rebleeding.

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Medical Hypotensive Therapy:
Medical—hypotensive therapy for ruptured intracranial aneurysms was introduced by Paul Slosberg MD (1926 – ; currently in practice) at the Mount Sinai Hospital in 1956 and was shown superior to surgery and other treatments in the largest randomized controlled study (multinational—15 institutions) ever conducted. This was reported in the major neurologic journal Stroke years ago but was underpublicized. More recently, with modifications for unruptured brain aneurysms and review of 50 years’ results it has again been found superior to surgical and now also to endovascular treatment. The method has the extreme cost-benefit advantage of completely eliminating the need for hospitalization itself, thereby eliminating surgical costs, endovascular costs, operating room costs and recovery room costs. In addition, it enables patients to completely avoid life-threatening nosocomial i.e. hospital-based, infections especially the frequently fatal MRSA infections along with other fatal hospital-based infections now being reported. This entirely medical treatment is performed by the neurologist both early and in long-term follow-up, in a private office or outpatient hospital facility. Aneurysms have been treated successfully regardless of size(e.g. giant aneurysms are included), location, complicating medical illnesses etc. These long term clinical results are buttressed by long-term MRA and CTA radiographic results showing that instead of the expected increase in size, the aneurysms either remain the same size, decrease in size or are no longer even visualized. This entirely medical method has now been endorsed by least two aneurysm surgical groups in England, as reported in both the Journal of Neurosurgery and Lancet Neurology.

Surgical clipping:..
Surgical clipping was introduced by Walter Dandy of the Johns Hopkins Hospital in 1937. It consists of performing a craniotomy, exposing the aneurysm, and closing the base of the aneurysm with a clip chosen specifically for the site. The surgical technique has been modified and improved over the years. Surgical clipping has a lower rate of aneurysm recurrence after treatment.

In January 2009, a team of doctors at UNC Hospital in Chapel Hill, North Carolina pioneered a new approach for aneurysm treatment – clipping aneurysms through an endoscopic endonasal approach. The team was led by UNC neurosurgeon, Dr. Anand Germanwala. This procedure may be groundbreaking for patients with aneurysms near the skull base, as an approach through the nose is less invasive than traditional approaches. Two videos related to this procedure can be seen on the UNC Neurosurgery website: http://www.med.unc.edu/neurosurgery/news/germanwala-presents-first-aneurysm-patient-treated-through-nose and http://www.med.unc.edu/neurosurgery/news/video-it-takes-two-or-more.

Endovascular coiling:.……
Endovascular coiling was introduced by Guido Guglielmi at UCLA in 1991. It consists of passing a catheter into the femoral artery in the groin, through the aorta, into the brain arteries, and finally into the aneurysm itself. Once the catheter is in the aneurysm, platinum coils are pushed into the aneurysm and released. These coils initiate a clotting or thrombotic reaction within the aneurysm that, if successful, will eliminate the aneurysm. These procedures require a small incision, through which a catheter is inserted. In the case of broad-based aneurysms, a stent may be passed first into the parent artery to serve as a scaffold for the coils (“stent-assisted coiling”), although the long-term studies of patients with intracranial stents have not yet been done.

Benefits & Risk:-
At this point it appears that the risks associated with surgical clipping and endovascular coiling, in terms of stroke or death from the procedure, are the same. The ISAT trials have shown, however, that patients who have experienced aneurysmal rupture have a 7% lower mortality rate when treated by coiling than patients treated by clipping, when all other factors are equal. Coiled aneurysms, however, do have a higher recurrence rate as demonstrated by angiography. For instance, the 2007 study by Jacques Moret and colleagues from Paris, France, (a group with one of the largest experiences in endovascular coiling) indicates that 28.6% of aneurysms recurred within one year of coiling, and that the recurrence rate increased with time. These results are similar to those previously reported by other endovascular groups. For instance Jean Raymond and colleagues from Montreal, Canada, (another group with a large experience in endovascular coiling) reported that 33.6% of aneurysms recurred within one year of coiling. The most recent data from Moret’s group reveals even higher aneurysm recurrence rates, namely a 36.5% recurrence rate at 9 months (which breaks down as 31.1% for small aneurysms less than 10 mm, and 56.0% for aneurysms 10 mm or larger). However, no studies to date have shown that the higher angiographic recurrence rate equals a higher rate of rebleeding. Thus far, the ISAT trials listed above show no increase in the rate of rebleeding, and show a persistent 7% lower mortality rate in subarachnoid hemorrhage patients who have been treated with coiling. In ISAT, the need for late retreatment of aneurysms was 6.9 times more likely for endovascular coiling as compared to surgical clipping. Furthermore, data from the ISAT group in March 2008 indicates that the higher aneurysm rate of recurrence is associated with a higher rebleeding rate, given that the rebleed rate of coiled aneurysms appears to be 8 times higher than that of surgically treated aneurysms in the ISAT study.

Therefore it appears that although endovascular coiling is associated with a shorter recovery period as compared to surgical clipping, it is also associated with a significantly higher recurrence rate after treatment. The long-term data for unruptured aneurysms are still being gathered.

Patients who undergo endovascular coiling need to have several serial studies (such as MRI/MRA, CTA, or angiography) to detect early recurrences. If a recurrence is identified, the aneurysm may need to be retreated with either surgery or further coiling. The risks associated with surgical clipping of previously-coiled aneurysms are very high. Ultimately, the decision to treat with surgical clipping versus endovascular coiling should be made by a cerebrovascular team with extensive experience in both modalities.

Prognosis:
The prognosis for a patient with a ruptured cerebral aneurysm depends on the extent and location of the aneurysm, the person’s age, general health, and neurological condition. Some individuals with a ruptured cerebral aneurysm die from the initial bleeding. Other individuals with cerebral aneurysm recover with little or no neurological deficit. The most significant factors in determining outcome are grade (see Hunt and Hess grade above) and age. Generally patients with Hunt and Hess grade I and II hemorrhage on admission to the emergency room and patients who are younger within the typical age range of vulnerability can anticipate a good outcome, without death or permanent disability. Older patients and those with poorer Hunt and Hess grades on admission have a poor prognosis. Generally, about two thirds of patients have a poor outcome, death, or permanent disability.

Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose.

Resources:
http://www.webmd.com/brain/tc/brain-aneurysm-topic-overview
http://www.nlm.nih.gov/medlineplus/brainaneurysm.html
http://en.wikipedia.org/wiki/Cerebral_aneurysm
http://www.bbc.co.uk/health/physical_health/conditions/brainaneurysm.shtml
http://www.nlm.nih.gov/medlineplus/ency/imagepages/17031.htm

http://www.yalemedicalgroup.org/stw/Page.asp?PageID=STW029076

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