A cerebral aneurysm occurs at a weak point in the wall of a blood vessel (artery) that supplies blood to the brain. Because of the flaw, the artery wall bulges outward and fills with blood. This bulge is called an aneurysm. An aneurysm can rupture, spilling blood into the surrounding body tissue. A ruptured cerebral aneurysm can cause permanent brain damage, disability, or death.

A cerebral aneurysm can occur anywhere in the brain. Aneurysms can have several shapes. The saccular aneurysm, once called a berry aneurysm, resembles a piece of fruit dangling from a branch. Saccular aneurysms are usually found at a branch in the blood vessel where they balloon out by a thin neck. Saccular cerebral aneurysms most often occur at the branch points of large arteries at the base of the brain. Aneurysms may also take the form of a bulge in one wall of the artery—a lateral aneurysm—or a widening of the entire artery—a fusiform aneurysm.

Some aneurysms may have a genetic link and run in families. The genetic link has not been completely proven and a pattern of inheritance has not been determined. Some studies seem to show that first-degree relatives of people who suffered aneurysmal subarachnoid hemorrhage (SAH) are more likely to have aneurysms themselves. These studies reported that such immediate family members were four times more likely to have aneurysms than the general population. Other studies do not confirm these findings. Better evidence links aneurysms to certain rare diseases of the connective tissue. These diseases include Marfan syndrome, pseudoxanthoma elasticum, Ehlers-Danlos syndrome, and fibromuscular dysplasia. Polycystic kidney disease is also associated with cerebral aneurysms.

These diseases are also associated with an increased risk of aneurysmal rupture. Certain other conditions raise the risk of rupture, too. Most aneurysms that rupture are a half-inch or larger in diameter. Size is not the only factor, however, because smaller aneurysms also rupture. Cigarette smoking, excessive alcohol consumption, and recreational drug use (for example, use of cocaine) have been linked with an increased risk. The role, if any, of high blood pressure has not been determined. Some studies have implicated high blood pressure in aneurysm formation and rupture, but people with normal blood pressure also experience aneurysms and SAH. High blood pressure may be a risk factor but not the most important one. Pregnancy, labor, and delivery also seem to increase the possibility that an aneurysm might rupture, but not all doctors agree. Physical exertion and use of oral contraceptives are not suspected causes for aneurysmal rupture.

Studies have shown a strong link to family history. If an immediate family member has suffered an aneurysm, you are 4 times more likely to have one as well. The genetic link is not completely understood and studies are underway to determine if there is a pattern of inheritance. The most important inherited conditions associated with aneurysms include Ehlers-Danlos IV, Marfan's syndrome, neurofibromatosis NF1, and polycystic kidney disease.

Risk factors for aneurysmal SAH currently being studied are smoking, high blood pressure, alcohol, genetic (family inherited), atherosclerosis, oral contraceptives, and lifestyle.

●Risk factors that doctors and researchers believe contribute to t Smoking

●High blood pressure or hypertension

●Congenital resulting from inborn abnormality in artery wall

●Family history of brain aneurysms

●Age over 40

●Gender, women compared with men have an increased incidence of aneurysms at a ratio of 3:2

●Other disorders: Ehlers-Danlos Syndrome, Polycystic Kidney Disease, Marfan Syndrome, and Fibromuscular Dysplasia (FMD)

●Presence of an arteriovenous malformation (AVM)

●Drug use, particularly cocaine

●Infection

●Tumors

●Traumatic head injury

●Smoking

●High blood pressure or hypertension

Most aneurysms go unnoticed until they rupture. However, 10-15% of unruptured cerebral aneurysms are found because of their size or their location. Common warning signs include symptoms that affect only one eye, such as an enlarged pupil, a drooping eyelid, or pain above or behind the eye. Other symptoms are a localized headache, unsteady gait, a temporary problem with sight, double vision, or numbness in the face.

Some aneurysms bleed occasionally without rupturing. Symptoms of such an aneurysm develop gradually. The symptoms include headache, nausea, vomiting, neck pain, black-outs, ringing in the ears, dizziness, or seeing spots.

Eighty to ninety percent of aneurysms are not diagnosed until after they have ruptured. Rupture is not always a sudden event. Nearly 50% of patients who have aneurysmal SAH also experience “the warning leak phenomenon.” Persons with warning leak symptoms have sudden, atypical headaches that occur days or weeks before the actual rupture. These headaches are referred to as sentinel headaches. Nausea, vomiting, and dizziness may accompany sentinel headaches. Unfortunately, these symptoms can be confused with tension headaches or migraines, and treatment can be delayed until rupture occurs.

When an aneurysm ruptures, most victims experience a sudden, extremely severe headache. This headache is typically described as the worst headache of the victim's life. Nausea and vomiting commonly accompany the headache. The person may experience a short loss of consciousness or prolonged coma. Other common signs of a SAH include a stiff neck, fever, and a sensitivity to light. About 25% of victims experience neurological problems linked to specific areas of the brain, swelling of the brain due to fluid accumulation (hydrocephalus), or seizure.

Most people find out they have an unruptured aneurysm by chance (incidental) during a scan for some other medical problem. If you are experiencing symptoms and your primary care doctor suspects an aneurysm, you may be referred to a neurosurgeon. The doctor will learn as much about your symptoms, current and previous medical problems, current medications, family history, and perform a physical exam. Diagnostic tests are used to help determine the aneurysm's location, size, type, and involvement with other structures.

Computed Tomography Angiography (CTA) scan is a noninvasive X-ray to review the anatomical structures within the brain to detect blood in or around the brain. A newer technology called CT angiography involves the injection of contrast into the blood stream to view the arteries of the brain. This type of test provides the best pictures of blood vessels through angiography and soft tissues through CT.

Angiogram is an invasive procedure, where a catheter is inserted into an artery and passed through the blood vessels to the brain. Once the catheter is in place, a contrast dye is injected into the bloodstream and the X-ray images are taken.

Magnetic resonance imaging (MRI) scan is a noninvasive test, which uses a magnetic field and radio-frequency waves to give a detailed view of the soft tissues of your brain. An MRA (Magnetic Resonance Angiogram) is the same non-invasive study, except it is also an angiogram, which means it also examines the blood vessels, as well as the structures of the brain.

When a patient is brought to the emergency room with a suspected ruptured aneurysm, doctors will learn as much as possible about his or her symptoms, current and previous medical problems, medications, and family history. A physical exam will be performed. Diagnostic tests will help determine the source of the bleeding.

Computed Tomography (CT) scan is a noninvasive X-ray that provides images of anatomical structures within the brain. It is especially useful to detect blood in or around the brain. A newer technology called CT angiography (CTA) involves the injection of contrast into the blood stream to view the arteries of the brain. CTA provides the best pictures of blood vessels (through angiography) and soft tissues (through CT).

Lumbar puncture is an invasive procedure in which a hollow needle is inserted into the subarachnoid space of the spinal canal to detect blood in the cerebrospinal fluid (CSF). The doctor will collect 2 to 4 tubes of CSF.

Angiogram is an invasive procedure in which a catheter is inserted into an artery and passed through the blood vessels to the brain. Once the catheter is in place, contrast dye is injected into the bloodstream and X-rays are taken.

Magnetic Resonance Imaging (MRI) scan is a noninvasive test that uses a magnetic field and radio-frequency waves to give a detailed view of the soft tissues of the brain. An MRA (Magnetic Resonance Angiogram) is the same non-invasive study, except that it is also an angiogram, which means it examines the blood vessels in addition to structures of the brain.

Deciding how, or even if, to treat an unruptured aneurysm involves weighing the risks of rupture versus the risks of treatment. The risk of aneurysm rupture is about 1% but may be higher or lower depending on the size and location of the aneurysm; however, when a rupture occurs there is a 50% risk of death. Risk factors for rupture include smoking, high blood pressure, alcohol, genetic factors (family inherited), atherosclerosis (hardening of the arteries), oral contraceptives, and lifestyle. Other factors such as the size and location of the aneurysm, overall health of the patient, and medical history must also be considered. Generally, the larger the aneurysm, the higher risk of rupture. Also, aneurysms in the posterior circulation (basilar, vertebral and posterior communicating arteries) have a higher risk of rupture. The neurosurgeon will discuss with you all the options and recommend a treatment that is best for your individual case.

Sometimes the best treatment may be to simply watch and reduce your risk of rupture (quit smoking, control high blood pressure). Aneurysms that are small, unruptured, and asymptomatic may be observed with imaging scans every year until the growth or symptoms necessitate surgery. Observation may be the best option for patients with other health conditions.

The most common treatment for an aneurysm is direct surgical clipping. Using general anesthesia, an opening is made in the skull, called a craniotomy. The brain is gently retracted so that the artery with the aneurysm may be located. A small clip is placed across the neck of the aneurysm to block the normal blood flow from entering the aneurysm. The clip is made of titanium and remains on the artery permanently.

If surgical clipping is not possible or the artery is too damaged, the surgeon may completely block (occlude) the artery that has the aneurysm. The blood flow is detoured (bypassed) around the occluded section of artery by inserting a vessel graft. The graft is a small artery, usually taken from your leg, that is connected above and below the blocked artery so that blood flow is rerouted (bypassed) through the graft.

A bypass can also be created by detaching a donor artery from its normal position on one end, redirecting it to the inside of the skull, and connecting it above the blocked artery. This is called a STA-MCA (superficial temporal artery to middle cerebral artery) bypass.

In contrast to surgery, another form of treatment is endovascular coiling. This is performed in the angiography suites of the radiology department by a neuro interventionalist and sometimes requires general anesthesia. In a coiling procedure, a catheter is inserted into an artery in the groin and then passed through the blood vessels to the aneurysm. The doctor guides the catheter through the bloodstream while watching a fluoroscopy (a type of X-ray) monitor. Through the catheter, the aneurysm is packed with material, either platinum coils or balloons, that prevents blood flow into the aneurysm. Since coiling is a relatively new procedure, follow-up angiograms are performed periodically to confirm the aneurysm is still occluded and not growing larger.

Treatment may include lifesaving measures, symptom relief, repair of the bleeding aneurysm, and complication prevention. For 10 to 14 days following an aneurysm rupture, the patient will remain in the neuroscience intensive care unit (NSICU), where doctors and nurses can watch closely for signs of renewed bleeding, vasospasm, hydrocephalus, and other potential complications.

Pain medication will be given to alleviate headache, anticonvulsant medication may be prescribed to prevent or treat seizures, and a vasodilator will be prescribed to prevent vasospasm. Blood pressure is lowered to reduce further bleeding and to control intracranial pressure.

Determining the best surgical treatment for a ruptured aneurysm involves many factors, such as the size, location, and type of aneurysm as well as the overall health of the patient and their medical history.

●Surgical clipping: an opening is made in the skull, called a craniotomy, to locate the aneurysm. A small clip is placed across the “neck” of the aneurysm to block the normal blood flow from entering. The clip is made of titanium and remains on the artery permanently.

●Endovascular coiling: is performed during an angiogram in the radiology department and sometimes requires general anesthesia. A catheter is inserted into an artery in the groin and then passed through the blood vessels to the aneurysm. Through the catheter, the aneurysm is packed with platinum coils or acrylic glue, which prevents blood flow into the aneurysm.

●Artery occlusion and bypass: if surgical clipping is not possible or the artery is too damaged, the surgeon may completely block (occlude) the artery that has the aneurysm. The blood flow is detoured (bypassed) around the occluded section of artery by inserting a vessel graft. The graft is a small artery, usually taken from your leg, that is connected above and below the blocked artery so that blood flow is rerouted (bypassed) through the graft.

A bypass can also be created by detaching a donor artery from its normal position on one end, redirecting it to the inside of the skull, and connecting it above the blocked artery.

aneurysm ['ænjə,rizəm] n.动脉瘤

angiography [,ændʒi'ɑgrəf] n.血管造影

basilar ['bæsəlɚ] adj.（尤指颅骨）基部的，底部的

bypass ['bai,pæs] n.旁路

dizziness ['dizinəs] n.头昏眼花

hydrocephalus [,haidro'sɛfələs] n.脑水肿，脑积水

vasospasm ['vezo,spæzəm] n.血管痉挛

anticonvulsant medication 抗惊厥药

Computed Tomography Angiography (CTA) CT血管造影

double vision 复视

Ehlers Danlos Syndrome 埃勒斯-当洛综合征

endovascular coiling 血管内栓塞

fibromuscular dysplasia 纤维肌性发育不良

lumbar puncture 腰椎穿刺

Magnetic Resonance Imaging (MRI) 磁共振成像

Magnetic Resonance Angiogram (MRA) 磁共振血管造影

Marfan Syndrome 马方综合征

middle cerebral artery 大脑中动脉

neurofibromatosis NF1 神经纤维瘤病1型

neurointerventionalist 神经介入专家

pseudoxanthoma elasticum 弹性假黄色瘤

saccular aneurysm 囊状动脉瘤

subarachnoid hemorrhage (SAH) 蛛网膜下出血

superficial temporal artery 颞浅动脉

surgical clipping 手术夹闭