| A cerebral aneurysm (also known as an intracranial or | | | | Most cerebral aneurysms result from an inborn |
| intracerebral aneurysm) is a weak or thin spot on a | | | | abnormality in an artery wall. Cerebral aneurysms are |
| blood vessel in the brain that balloons out and fills with | | | | also more common in people with certain genetic |
| blood. The bulging aneurysm can put pressure on a | | | | diseases, such as connective tissue disorders and |
| nerve or surrounding brain tissue. It may also leak or | | | | polycystic kidney disease, and certain circulatory |
| rupture, spilling blood into the surrounding tissue (called a | | | | disorders, such as arteriovenous malformations - |
| hemorrhage). Some cerebral aneurysms, particularly | | | | congenital malformations in which a snarled tangle of |
| those that are very small, do not bleed or cause other | | | | arteries and veins in the brain disrupts blood flow. |
| problems. Cerebral aneurysms can occur anywhere in | | | | The signs and symptoms of an unruptured cerebral |
| the brain, but most are located along a loop of arteries | | | | aneurysm will partly depend on its size and rate of |
| that run between the underside of the brain and the | | | | growth. For example, a small, unchanging aneurysm will |
| base of the skull. | | | | generally produce no symptoms, whereas a larger |
| Cerebral aneurysms are pathologic focal dilatations of | | | | aneurysm that is steadily growing may produce |
| the cerebrovasculature that are prone to rupture. | | | | symptoms such as loss of feeling in the face or |
| These vascular abnormalities are classified by | | | | problems with the eyes. Immediately before an |
| presumed pathogenesis. Saccular, berry, or congenital | | | | aneurysm ruptures, an individual may experience such |
| aneurysms constitute 90% of all cerebral aneurysms | | | | symptoms as a sudden and unusually severe |
| and are located at the major branch points of large | | | | headache, nausea, vision impairment, vomiting, and loss |
| arteries. Dolichoectatic, fusiform, or arteriosclerotic | | | | of consciousness. |
| aneurysms are elongated outpouchings of proximal | | | | Most aneurysms go unnoticed until they rupture. In |
| arteries that account for 7% of all cerebral aneurysms. | | | | about 10 to 15 percent of cases, however, there are |
| Infectious or mycotic aneurysms are situated | | | | symptoms. Common warning signs include an enlarged |
| peripherally and comprise 0.5% of all cerebral | | | | pupil in one eye, a drooping eyelid, or pain above or |
| aneurysms. Other peripheral lesions include neoplastic | | | | behind the eye. Other symptoms include a headache in |
| aneurysms, rare sequelae of embolized tumor | | | | one specific part of the head, difficulty in walking, |
| fragments, and traumatic aneurysms. | | | | double vision, or numbness in the face. |
| A common location of cerebral aneurysms is on the | | | | Diagnosis of a ruptured cerebral aneurysm is |
| arteries at the base of the brain, known as the Circle | | | | commonly made by finding signs of subarachnoid |
| of Willis. Approximately 85% of cerebral aneurysms | | | | hemorrhage on a CT scan (Computerized |
| develop in the anterior part of the Circle of Willis, and | | | | Tomography, sometimes called a CAT scan). The CT |
| involve the internal carotid arteries and their major | | | | scan is a computerized test that rapidly X-rays the |
| branches that supply the anterior and middle sections | | | | body in cross-sections, or slices, as the body is moved |
| of the brain. The most common sites include the | | | | through a large, circular machine. If the CT scan is |
| anterior communicating artery (30-35%), the bifurcation | | | | negative but a ruptured aneurysm is still suspected, a |
| of the internal carotid and posterior communicating | | | | lumbar puncture is performed to detect blood in the |
| artery (30-35%), the bifurcation of the middle cerebral | | | | cerebrospinal fluid (CSF) that surrounds the brain and |
| artery (20%), the bifurcation of the basilar artery, and | | | | spinal cord. |
| the remaining posterior circulation arteries (5%). | | | | |