Cerebral (Brain) Aneurysms

A cerebral aneurysm is an abnormal outward bulging on the vessel wall ofan artery in the brain. The prevalence of intracranial aneurysms has beenestimated between 0.5 and 6 percent. Aneurysms may be as small as 1 to2 mm (0.04 to 0.08 inches). Those 25 mm (0.98 inches) or greater in sizeare termed giant aneurysms. Aneurysms seem to rupture most commonlyin persons 40 to 60 years old. Cerebral aneurysms which have previouslyruptured are prone to re-rupture. In addition, aneurysms which are caus-ing symptoms such as headache or double vision appear to be at higherrisk for bleeding. The risk increases with the size of the aneurysm.

Aneurysms are commonly classified by shape, as described below:

Saccular or Berry Most frequent cerebral aneurysm. Arises commonly at branching points or curves in brain arteries.

Fusiform Tend to occur on vessels as a result of atherosclerotic loss of elasticity or from dissections. Most often seen in the vertebral or basilar artery. Similar in shape to aneurysms of the aorta.

Dissecting May occur after trauma or spontaneously. Development of a tear in the intima (the inner layer of an artery) allows blood to force apart the layers of the arterial wall, forming a false lumen.

Pseudoaneurysm Organized hematoma from a vessel that has bled. No true vessel walls exist in this aneurysm. Pathologically distinguished by concentric rings of fibrin and organized blood. Often are traumatic or infectious in origin.

Neoplastic Result from microscopic pieces of tumor and subsequent growth of the neoplasm through the vessel wall. Seen with atrial myxoma and choriocarcinoma.

Infectious (Mycotic) Usually arise at the sites of microemboli from cardiac or pulmonary infections. Bacteria or fungi are known to be the causative agents. Loss of elastic tissue and damage to the intima (due to inflammatory disease) are the characteristic pathologies.

Although most aneurysms occur sporadically, there is a familial incidence (7 to 20 percent of patients withaneurysmal subarachnoid hemorrhage have a first- or second-degree relative with a confirmed intracranialaneurysm), with siblings having the highest association. Certain conditions, particularly connective tissue disor-ders or abnormalities of blood flow, have an increased propensity for aneurysms.

Rupture of a cerebral aneurysm carries a significant morbidity and mortality rate. Approximately 80 percent ofnon-traumatic subarachnoid hemorrhages are the result of rupture of an intracranial aneurysms. Cigarette smok-ing is associated with three to 10 times the risk of aneurysmal subarachnoid hemorrhage. Patients with untreatedruptured aneurysms continue to have a substantial long-term risk, as an aneurysm which has ruptured once has ahigh risk of rupturing again.

Cerebral (Brain) Aneurysms

Aneurysm DiagnosisUnruptured aneurysms are most likely to be discovered during conventional or magnetic resonance (MR) angiog-raphy. Magnetic resonance angiography and CT angiography are being used increasingly to screen patients withsuspicious headache and family history of intracranial hemorrhage.

Arterial contrast angiography is performed to eliminate vascular overlap and provide stereoscopic images ofaneurysms. Rotational angiography and angiography with three-dimensional reconstruction provide excellentvisualization of the anatomical arrangement of the aneurysm. In this procedure, a thin catheter is introduced intothe femoral artery in the groin and then steered through the blood vessels of the body to the artery involved inthe aneurysm. This procedure is performed in an angiography suite “cath lab.” X-ray imaging allows the neuro-surgeon to view the vessels via a solution containing water and iodine salts (“contrast”), which is injectedthrough the catheter. The X-ray images provide detailed pictures of the location, size and shape of the aneurysm.

These questions are considered by the angiographer during the viewing procedure:• Is there an aneurysm? • What is the exact location of the aneurysm? • Is there one aneurysm or more than one? • If there is more than one aneurysm, which one bled or is likely to bleed in the future?• What is the size of the aneurysm? • Does the aneurysm have a neck, and what is the orientation of the neck and the dome? • What is the relationship of branch vessels to the aneurysm? • What is the status of the circle of Willis? • Is any other lesion associated with the aneurysm (e.g. extracranial occlusive vascular disease, vasculitis, AVM)? • Is there vasospasm?

Aneurysm Treatment Options“Should a cerebral aneurysm be ‘clipped’ or ‘coiled’?” This is a common question in the treatment of aneurysms.Occasionally, aneurysms are too complex in shape or too inundated with feeding arteries to be treated with a clip.In other cases, aneurysms are so hidden by complicated, sharp curving vasculature that a catheter cannot safelyaccess the aneurysm for coiling. In such situations, the decision to “clip” or “coil” is clearly determined. Inaneurysms without clear limiting factors for clipping or coiling, the treatment answer requires specific attentionto the details of each presenting aneurysm.

Surgical Clipping: To access the aneurysm, the neurosurgeon firstremoves a section of the skull in a procedure called a craniotomy. Oncethe aneurysm is located adjacent to the brain tissue, a tiny clip is placedacross the neck of the aneurysm to isolate it from normal circulation. Theclip is similar to a coil-spring clothespin, in that the clip blades remainclosed until pressure is applied to open the clip. Once the clip is securedto the aneurysm, the surgeon secures the bone to its original location andcloses the incision. The titanium clips remain on the aneurysm perma-nently.

Endovascular Coiling: Endovascular coiling is a minimally invasiveapproach that does not include open surgery. Instead, the endovascularneurosurgeon uses fluoroscopic imaging, a type of real-time X-ray tech-

nology, to view the patient's vascular system and place coils within the aneurysm from within the blood vessel.Endovascular treatment of brain aneurysms involves insertion of a catheter into the femoral artery in the groinregion and navigating it through the vascular system into the head and into the aneurysm. Tiny platinum coilsare threaded through the catheter to fill the aneurysm, blocking blood flow into the aneurysm and preventingrupture. This endovascular coiling (filling) of the aneurysm is called embolization.

A randomized, multi-centered trial recently compared the safety and efficiency ofendovascular coiling versus surgical clipping for ruptured aneurysms judged to besuitable for both treatments. This trial, the International Subarachnoid AneurysmTrial (ISAT), found that the outcome in terms of survival and disability at one yearwas significantly better with endovascular coiling. The data available to date sug-gest that the long-term risks of further bleeding from the treated aneurysms arelow with either therapy, although somewhat more frequent with endovascularcoiling. The published results of the ISAT trial are taken into consideration whendetermining the most appropriate means of treatment for aneurysms.

Frequently Asked QuestionsShould I have surgery on my unruptured aneurysm? Dr. William Thorell, M.D., a neurosurgeon at The Nebraska Medical Center, is committed toproviding careful counseling for patients and their families regarding the risks and benefits oftreatment. The size, shape and location of each aneurysm influence the surgical outcome.Certain aneurysms present with features which make the risk of surgical correction greaterthan leaving the aneurysm untreated. Furthermore, patient-related factors such as age andmedical conditions have an influence on the likely outcome of treatment. Since scientificstudies have not yet quantified every aspect of aneurysm intervention, the staff at TheNebraska Medical Center believes in providing individualized assistance to each patient con-sidering treatment.

How long will it take to coil or clip my aneurysm? Approximately four to six hours are needed to clip or coil an aneurysm. Based on the unique presenting factor of eachaneurysm, some procedures take more time, whereas other procedures take less.

Will I be awake for the procedures? No. General anesthesia is typically provided by one of the skilled members of the Anesthesia Department at The NebraskaMedical Center.

After surgery, when will I be able to resume my normal daily activities? Patients who have undergone coiling of an unruptured aneurysm usually return to normal daily activities within oneweek. Patients who have undergone clipping of an unruptured aneurysm usually return to normal daily activities withinone month.

I have additional questions about my aneurysm. How can I find answers? The Section of Neurosurgery at the University of Nebraska Medical Center is eager to respond to your health care con-cerns. Please call 402-559-3995 with any questions related to your aneurysm. We would be happy to suggest additionalreading materials or provide direct answers to your questions.

Cerebral (Brain) Aneurysms

Neurosurgical Service Offerings:

Cerebral AneurysmsCerebral Vascular MalformationsBrain HemorrhagesStrokesCarotid StenosesVertebral/Basilar StenosesTumors

Spinal DiseasesSpinal DegenerationSpinal TraumasPeripheral Nerve DiseasesCarpal Tunnel SyndromesUlnar Nerve DiseasesPeripheral Nerve Tumors

Contact Information:

William E. Thorell, M.D.982035 Nebraska Medical CenterOmaha, NE 68198-2035

Phone: 402.559.3995Fax: 402.559.7779