Cerebral aneurysm

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Cerebral aneurysm
Classification & external resources
DiseasesDB 1358
MedlinePlus 001414
eMedicine neuro/503  med/3468 radio/92

A cerebral or 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.

Contents

[edit] Locations

A common location of cerebral 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 communicating artery (30-35%), the bifurcation 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%).

[edit] Causes of cerebral aneurysms

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. They are slightly more common in women than in men.

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.

[edit] Classification of cerebral aneurysms

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

[edit] Symptoms of aneurysms

A small, unchanging aneurysm will produce no symptoms. Before a larger aneurysm ruptures, the individual may experience such symptoms as a sudden and unusually severe headache, nausea, vision impairment, vomiting, and loss of consciousness, or the individual may be asymptomatic, experiencing no symptoms at all. 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. The risk of short term re-rupture increases dramatically after an aneurysm has bled, though after approximately 6 weeks the risk returns to baseline.

[edit] Classification of ruptured aneurysm severity

In outlining symptoms of ruptured cerebral aneurysm, it is useful to make use of the Hunt and Hess scale of subarachnoid hemorrhage severity:

The Fischer Grade classifies the appearance of subarachnoid hemorrhage on CT scan:

  • Grade 1: No hemorrhage evident.
  • Grade 2: Subarachnoid hemorrhage less than 1mm thick.
  • Grade 3: Subarachnoid hemorrhage more than 1mm thick.
  • Grade 4: Subarachnoid hemorrhage of any thickness with intra-ventricular hemorrhage (IVH) or parenchymal extension.

The Fischer Grade is most useful in communicating the description of SAH. It is less useful prognostically than the Hunt-Hess scale.

[edit] Vasospasm

One complication of aneurysmal subarachnoid hemorrhage is the development of vasospasm. 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.

Vasospasm is monitored in a variety of ways. Non-invasive methods include transcranial Doppler, 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 scanning.

The definitive, but invasive method of detecting vasospasm is cerebral angiography. 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, increases blood 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 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.

[edit] Treatment

Emergency treatment for individuals with a ruptured cerebral aneurysm generally includes restoring deteriorating respiration and reducing intracranial pressure. Surgery is usually performed within the first three days to occlude the ruptured aneurysm and reduce the risk of rebleeding. Traditionally this was performed by neurosurgeons clipping the aneurysm, but increasingly this is performed by interventional neuroradiologists placing coils in the aneurysm. This new technique is less invasive. During these procedures, a thin, hollow tube (catheter) is inserted in the groin area and threaded through the blood vessels to the site of the aneurysm in the brain. Once the catheter reaches the aneurysm, tiny platinum coils are placed inside blocking blood flow and preventing rebleeding.

[edit] 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[citation needed].

[edit] See also

[edit] External links

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The base text for this article was taken from the National Institute of Neurological Disorders and Stroke public domain resource at http://www.ninds.nih.gov/health_and_medical/disorders/ceraneur_doc.htm.

  • [1] {Addressing the Challenges Faced as a Result of

Brain Haemorrhage.}

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