Cerebral aneurysm
A cerebral or brain aneurysm is a cerebrovascular
Cerebrovascular disease
Cerebrovascular disease is a group of brain dysfunctions related to disease of the blood vessels supplying the brain. Hypertension is the most important cause; it damages the blood vessel lining, endothelium, exposing the underlying collagen where platelets aggregate to initiate a repairing process...

 disorder in which weakness in the wall of a cerebral
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....

 or vein
In the circulatory system, veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart...

 causes a localized dilation
Vasodilation refers to the widening of blood vessels resulting from relaxation of smooth muscle cells within the vessel walls, particularly in the large arteries, smaller arterioles and large veins. The process is essentially the opposite of vasoconstriction, or the narrowing of blood vessels. When...

 or ballooning of the blood vessel.

Signs and symptoms

A small, unchanging aneurysm will produce little, if any, symptoms. Before a larger aneurysm ruptures, the individual may experience such symptoms as a sudden and unusually severe headache, nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...

, vision impairment, vomiting
Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...

, and loss of consciousness
Unconsciousness is the condition of being not conscious—in a mental state that involves complete or near-complete lack of responsiveness to people and other environmental stimuli. Being in a comatose state or coma is a type of unconsciousness. Fainting due to a drop in blood pressure and a...

, or the individual may be asymptomatic, experiencing no symptoms at all.

If an aneurysm ruptures, it leaks blood into the space around the brain. This is called a “subarachnoid hemorrhage.” Depending on the amount of blood, it can produce:
  • a sudden severe headache that can last from several hours to days
  • nausea and vomiting
  • drowsiness and/or coma

The ruptured aneurism (hemorrhage) may also damage the brain directly, usually from bleeding into the brain itself. This is called a “hemorrhagic stroke.” This can lead to:
  • weakness or paralysis of an arm or leg
  • trouble speaking or understanding language
  • vision problems
  • seizures


An aneurysm or aneurism is a localized, blood-filled balloon-like bulge in the wall of a blood vessel. Aneurysms can commonly occur in arteries at the base of the brain and an aortic aneurysm occurs in the main artery carrying blood from the left ventricle of the heart...

s may result from congenital defects, preexisting conditions such as high blood pressure and atherosclerosis
Atherosclerosis is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholesterol...

 (the buildup of fatty deposits in the arteries), or head trauma
Head injury
Head injury refers to trauma of the head. This may or may not include injury to the brain. However, the terms traumatic brain injury and head injury are often used interchangeably in medical literature....

. Cerebral aneurysms occur more commonly in adults than in children but they may occur at any age. They are more common in women than in men, by a ratio of 3 to 2.

The pursuit to identify Genetics of Intracranial Aneurysms has identified a number of locations, most recently 1p34-36, 2p14-15, 7q11, 11q25, and 19q13.1-13.3.


A common location of cerebral aneurysms is on the arteries at the base of the brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

, known as the Circle of Willis
Circle of Willis
The Circle of Willis is a circle of arteries that supply blood to the brain...

. Approximately 85% of cerebral aneurysms develop in the anterior part of the Circle of Willis
Circle of Willis
The Circle of Willis is a circle of arteries that supply blood to the brain...

, 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
Anterior communicating artery
In human anatomy, the anterior communicating artery is a blood vessel of the brain that connects the left and right anterior cerebral arteries....

 (30–35%), the bifurcation, division of two branches, of the internal carotid and posterior communicating artery
Posterior communicating artery
In human anatomy, the posterior communicating artery is one of a pair of right-sided and left-sided blood vessels in the circle of Willis. It connects the three cerebral arteries of the same side. Anteriorly, it connects to the internal carotid artery prior the terminal bifurcation of the ICA...

 (30–35%), the bifurcation of the middle cerebral artery
Middle cerebral artery
-External links:*...

 (20%), the bifurcation of the basilar artery
Basilar artery
In human anatomy, the basilar artery is one of the arteries that supplies the brain with oxygen-rich blood.The two vertebral arteries and the basilar artery are sometimes together called the vertebrobasilar system, which supplies blood to the posterior part of circle of Willis and anastomoses with...

, and the remaining posterior circulation arteries (5%).

Onset and risks

Onset is usually sudden and without warning. Rupture of a cerebral aneurysm is dangerous and usually results in bleeding into the meninges
The meninges is the system of membranes which envelopes the central nervous system. The meninges consist of three layers: the dura mater, the arachnoid mater, and the pia mater. The primary function of the meninges and of the cerebrospinal fluid is to protect the central nervous system.-Dura...

 or the brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

 itself, leading to a subarachnoid hemorrhage
Subarachnoid hemorrhage
A subarachnoid hemorrhage , or subarachnoid haemorrhage in British English, is bleeding into the subarachnoid space—the area between the arachnoid membrane and the pia mater surrounding the brain...

 (SAH) or intracranial hematoma
A hematoma, or haematoma, is a localized collection of blood outside the blood vessels, usually in liquid form within the tissue. This distinguishes it from an ecchymosis, which is the spread of blood under the skin in a thin layer, commonly called a bruise...

 (ICH), either of which constitutes a stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...

. Rebleeding, hydrocephalus
Hydrocephalus , also known as "water in the brain," is a medical condition in which there is an abnormal accumulation of cerebrospinal fluid in the ventricles, or cavities, of the brain. This may cause increased intracranial pressure inside the skull and progressive enlargement of the head,...

 (the excessive accumulation of cerebrospinal fluid
Cerebrospinal fluid
Cerebrospinal fluid , Liquor cerebrospinalis, is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord...

), vasospasm
Vasospasm refers to a condition in which blood vessels spasm, leading to vasoconstriction. This can lead to tissue ischemia and death . Cerebral vasospasm may arise in the context of subarachnoid hemorrhage. Symptomatic vasospasm or delayed cerebral ischemia is a major contributor to...

 (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.


Cerebral aneurysms are classified both by size and shape. Small aneurysms have a diameter of less than 15 mm. Larger aneurysms include those classified as large (15 to 25 mm), giant (25 to 50 mm), and super giant (over 50 mm). Saccular aneurysms are those with a saccular outpouching and are the least common form of cerebral aneurysm. Berry aneurysms are saccular aneurysms with necks or stems resembling a berry. Fusiform aneurysms are aneurysms without stems.

In outlining symptoms of ruptured cerebral aneurysm, it is useful to make use of the Hunt and Hess scale
Hunt and Hess scale
The Hunt and Hess scale is one of the grading systems used to classify the severity of a subarachnoid hemorrhage based on the patient's clinical condition. It is used as a predictor of patient's prognosis/outcome, with a higher grade correlating to lower survival rate...

  of subarachnoid hemorrhage severity:
  • Grade 1: Asymptomatic; or minimal headache
    A headache or cephalalgia is pain anywhere in the region of the head or neck. It can be a symptom of a number of different conditions of the head and neck. The brain tissue itself is not sensitive to pain because it lacks pain receptors. Rather, the pain is caused by disturbance of the...

     and slight nuchal rigidity.
  • Grade 2: Moderate to severe headache; nuchal rigidity; no neurologic
    Neurology is a medical specialty dealing with disorders of the nervous system. Specifically, it deals with the diagnosis and treatment of all categories of disease involving the central, peripheral, and autonomic nervous systems, including their coverings, blood vessels, and all effector tissue,...

     deficit except cranial nerve palsy
    In medicine, palsy is the paralysis of a body part, often accompanied by loss of sensation and by uncontrolled body movements, such as shaking. Medical conditions involving palsy include cerebral palsy , brachial palsy , and Bell's palsy ....

  • Grade 3: Drowsy; minimal neurologic deficit.
  • Grade 4: Stuporous; moderate to severe hemiparesis
    Hemiparesis is weakness on one side of the body. It is less severe than hemiplegia - the total paralysis of the arm, leg, and trunk on one side of the body. Thus, the patient can move the impaired side of his body, but with reduced muscular strength....

    ; possibly early decerebrate rigidity and vegetative disturbances.
  • Grade 5: Deep coma
    In medicine, a coma is a state of unconsciousness, lasting more than 6 hours in which a person cannot be awakened, fails to respond normally to painful stimuli, light or sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions. A person in a state of coma is described as...

    ; decerebrate rigidity; moribund.
  • Grade 6: Death. By definition, someone who presents brain dead following SAH is grade 6.

The Fisher Grade  classifies the appearance of subarachnoid hemorrhage on CT scan:
  • Grade 1: No hemorrhage evident.
  • Grade 2: Subarachnoid hemorrhage less than 1 mm thick.
  • Grade 3: Subarachnoid hemorrhage more than 1 mm thick.
  • Grade 4: Subarachnoid hemorrhage of any thickness with intra-ventricular hemorrhage (IVH) or parenchymal extension.

The Fisher Grade is most useful in communicating the description of SAH and stratifies patients' risk for vasospasm. It is not intended to be used as a prognostic scale, unlike the Hunt-Hess scale.


One complication of aneurysmal subarachnoid hemorrhage is the development of vasospasm
Vasospasm refers to a condition in which blood vessels spasm, leading to vasoconstriction. This can lead to tissue ischemia and death . Cerebral vasospasm may arise in the context of subarachnoid hemorrhage. Symptomatic vasospasm or delayed cerebral ischemia is a major contributor to...

. Approximately 1 to 2 weeks following the initial hemorrhage, patients may experience 'spasm' of the cerebral arteries, which can result in stroke. The etiology of vasospasm is thought to be secondary to an inflammatory process that occurs as the blood in the subarachnoid space is resorbed. It appears that macrophages and neutrophils that enter the subarachnoid space to phagocytose senescent erythrocytes and clear extracorpuscular hemoglobin, remain trapped in the subarachnoid space, die and degranulate 3–4 days after their arrival, and release massive quantities of endothelins and free radicals that in turn induce vasospasm. Vascular narrowing, however, is only one component of the transient inflammatory injury, which is extensive.

Vasospasm is monitored in a variety of ways. Non-invasive methods include transcranial Doppler
Transcranial doppler
Transcranial Doppler is a test that measures the velocity of blood flow through the brain's blood vessels. Used to help in the diagnosis of emboli, stenosis, vasospasm from a subarachnoid hemorrhage , and other problems, this relatively quick and inexpensive test is growing in popularity in the...

, which is a method of measuring the velocity of blood in the cerebral arteries using ultrasound. As the vessels narrow due to vasospasm, the velocity of blood increases. The amount of blood reaching the brain can also be measured by CT or MRI or nuclear perfusion
In physiology, perfusion is the process of nutritive delivery of arterial blood to a capillary bed in the biological tissue. The word is derived from the French verb "perfuser" meaning to "pour over or through."...


The definitive, but invasive method of detecting vasospasm is cerebral angiography
Cerebral angiography
Cerebral angiography is a form of angiography which provides images of blood vessels in and around the brain, thereby allowing detection of abnormalities such as arteriovenous malformations and aneurysms....

. It is generally agreed that in order to prevent or reduce the risk of permanent neurological deficits, or even death, vasospasm should be treated aggressively. This is usually performed by early delivery of drug and fluid therapy, or 'Triple H' (hypertensive-hypervolemic-hemodilution therapy) (which elevates blood pressure
Blood pressure
Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...

, increases blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

 volume, and thins the blood) to drive blood flow through and around blocked arteries. For patients who are refractive (resistant) to Triple H therapy, narrowed arteries in the brain can be treated with medication delivered into the arteries that are in spasm and with balloon angioplasty
Angioplasty is the technique of mechanically widening a narrowed or obstructed blood vessel, the latter typically being a result of atherosclerosis. An empty and collapsed balloon on a guide wire, known as a balloon catheter, is passed into the narrowed locations and then inflated to a fixed size...

 to widen the arteries and increase blood flow to the brain. Although the effectiveness of these treatments is well established, angioplasty and other treatments delivered by interventional radiologists have been in evolution over the past several years. It is generally recommended that aneurysms be evaluated at specialty centers which provide both neurosurgical and interventional radiology treatment and which also permit angioplasty, if needed, without transfer.


Emergency treatment
Emergency medicine
Emergency medicine is a medical specialty in which physicians care for patients with acute illnesses or injuries which require immediate medical attention. While not usually providing long-term or continuing care, emergency medicine physicians diagnose a variety of illnesses and undertake acute...

 for individuals with a ruptured cerebral aneurysm generally includes restoring deteriorating respiration
Respiration (physiology)
'In physiology, respiration is defined as the transport of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction...

 and reducing intracranial pressure
Intracranial pressure
Intracranial pressure is the pressure inside the skull and thus in the brain tissue and cerebrospinal fluid . The body has various mechanisms by which it keeps the ICP stable, with CSF pressures varying by about 1 mmHg in normal adults through shifts in production and absorption of CSF...

. 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.

Hypotensive therapy

Medical—hypotensive therapy for ruptured intracranial aneurysms was introduced by Paul Slosberg MD ( currently in private 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.
It is not considered standard management of acute intracranial aneurysm rupture in the UK.

Surgical clipping

Surgical clipping was introduced by Walter Dandy
Walter Dandy
Walter Edward Dandy, M.D. was an American neurosurgeon and scientist. He is considered one of the founding fathers of neurosurgery, along with Victor Horsley and Harvey Cushing...

 of the Johns Hopkins Hospital
Johns Hopkins Hospital
The Johns Hopkins Hospital is the teaching hospital and biomedical research facility of Johns Hopkins University School of Medicine, located in Baltimore, Maryland . It was founded using money from a bequest by philanthropist Johns Hopkins...

 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 and risks

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
Subarachnoid hemorrhage
A subarachnoid hemorrhage , or subarachnoid haemorrhage in British English, is bleeding into the subarachnoid space—the area between the arachnoid membrane and the pia mater surrounding the brain...

 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.


The prognosis
Prognosis is a medical term to describe the likely outcome of an illness.When applied to large statistical populations, prognostic estimates can be very accurate: for example the statement "45% of patients with severe septic shock will die within 28 days" can be made with some confidence, because...

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.

External links

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