A cerebral or intracranial aneurysm is a dilation of an artery in the brain that results from a weakening of the inner muscular layer (the intima) of a blood vessel wall. The vessel develops a blister-like dilation that can become thin and rupture without warning. The resultant bleeding into the space around the brain is called a subarachnoid hemorrhage (SAH). This kind of hemorrhage can lead to a stroke, coma and/or death. Several factors are believed to contribute to the formation of cerebral aneurysms. These include:
- Hypertension (high blood pressure)
- Cigarette smoking
- Congenital (genetic) predisposition
- Injury or trauma to blood vessels
- Complication from some types of blood infections
People who suffer a ruptured brain aneurysm may have warning signs, including:
- Localized migraine-like headache
- Nausea and vomiting
- Stiff neck
- Blurred or double vision
- Sensitivity to light (photophobia)
- Loss of sensation
Many people with unruptured brain aneurysms have no symptoms. Others might experience some or all of the following symptoms, which may be possible signs of an aneurysm:
- Cranial nerve palsy
- Dilated pupils
- Double vision
- Pain above and behind eye
- Localized headache
- Progressive weakness or numbness
Computed Tomography (CT or CAT scan)
A diagnostic image created after a computer reads x-rays. In some cases, a medication will be injected through a vein to help highlight brain structures. Bone, blood and brain tissue have very different densities and can easily be distinguished on a CT scan. A CT scan is a useful diagnostic test for hemorrhagic strokes because blood can easily be seen. CT Angiography (CTA) is a special CT scan using contrast dye to highlight the arteries of the brain and is becoming at least the initial preferred diagnostic method if an aneurysm is suspected.
Magnetic Resonance Angiogram (MRA)
This is a noninvasive study which is conducted in a magnetic resonance imager. The magnetic images are assembled by a computer to provide an image of the arteries in the head and neck. The MRA shows the actual blood vessels and can help detect blockage and aneurysms. MRA does not provide more information about a cerebral aneurysm than a CTA of good quality, and takes much longer to perform (about 35 minutes). It is also contraindicated in patients with certain types of metallic implants. Its advantages over CTA are that 1) patients with iodine allergy are not excluded; 2) there is no exposure to ionizing radiation.
Cerebral Angiography (also called cerebral angiogram, carotid/vertebral angiogram)
An invasive test where a catheter is inserted into the femoral artery of the leg and contrast dye is then injected. X-rays are then taken to give a complete picture of the arteries and veins of the brain. Because the test is invasive, cerebral angiography carries a measurable though small (0.5 percent) risk of stroke. Cerebral angiography is considered the gold standard test for evaluation of the blood vessels of the central nervous system.
Observation is considered a reasonable option if the aneurysm is very small or in a location that is felt to present a low risk of growth or rupture. If the aneurysm has ruptured or is considered large enough to pose significant risk for rupture, then treatment is usually recommended. Microsurgical clipping is performed through a craniotomy with small titanium clips to completely exclude the aneurysm from the circulation. Another option is endovascular coiling, which uses a microcatheter to feed coils inside the dome of the aneurysm to clot it off from the circulation. Both means of treatment have their risks and benefits and should be discussed with your surgeon in the decision-making process.