A cerebral aneurysm (also known as an intracranial or intracerebral aneurysm) is a weak or thin spot on a blood vessel in the brain that balloons out and fills with blood. Cerebral aneurysms can occur anywhere in the brain; very often they are found on the large arteries at the base of the brain at the points where arteries branch off. Although cerebral (brain) aneurysms are much more common in adults than in children, they can occur in anyone and at any age.
Some cerebral aneurysms, particularly those that are very small, do not bleed or cause other problems. Small aneurysms are less than 11 millimeters in diameter (about the size of a standard pencil eraser), larger aneurysms are 11–25 millimeters (about the size of a dime), and giant aneurysms are greater than 25 millimeters in diameter (more than the size of a quarter).
What Causes Cerebral Aneurysms?
Cerebral aneurysms can be congenital (present at birth), resulting from an inborn abnormality in an artery wall. They also are more common in people with certain genetic diseases, such as connective tissue disorders or polycystic kidney disease. They can be associated with other brain abnormalities such as an arteriovenous malformation (snarled tangles of arteries and veins in the brain that disrupt blood flow). This occurs roughly 10 percent of the time.
In children, especially, brain aneurysms may also result from a head injury, an infection in an arterial wall or may be associated with cancerous tumors of the head and neck. Aneurysms of these types tend to present most often as subarachnoid hemorrhages (bleeding between the brain and its surrounding membrane, the arachnoid).
Possible risk factors for rupture in adults include hypertension, alcohol abuse, drug abuse (particularly cocaine) and smoking.
What Are the Symptoms of Cerebral Aneurysms?
Most cerebral aneurysms do not show symptoms until they either become very large or burst. Small, unchanging aneurysms generally do not produce symptoms, whereas a larger aneurysm that is steadily growing may press on tissues and nerves. Symptoms may include the following:
- Pain above and behind the eye
- Numbness, weakness or paralysis on one side of the face
- Dilated pupils; and vision changes (double or loss of vision)
When an aneurysm ruptures, an individual may experience the following:
- Sudden and extremely severe headache (“the worst headache ever”)
- Double vision
- Stiff neck and/or loss of consciousness
How Are Cerebral Aneurysms Diagnosed?
Most cerebral aneurysms are not found until they rupture or are detected by brain imaging that may have been obtained for another condition. Several diagnostic methods are available to provide information about the aneurysm and the best form of treatment:
- A digital subtraction cerebral angiogram
- Computed tomography angiogram (CT/CTA)
- Magnetic resonance imaging (MRI/MRA)
Cerebrospinal fluid analysis may be ordered if a ruptured aneurysm is suspected but is not clearly present on CT. Following application of a local anesthetic, a small amount of this fluid (which protects the brain and spinal cord) is removed by a needle and tested to detect any bleeding or brain hemorrhage.
What Is the Treatment for Cerebral Aneurysms?
Not all cerebral aneurysms burst. Some individuals with very small aneurysms may be monitored to detect any growth or onset of symptoms and to ensure aggressive treatment of coexisting medical problems and risk factors. Each case is unique, and considerations for treating an unruptured aneurysm include the type, size and location of the aneurysm; annual risk of rupture; patient’s age, health and personal and family medical history; and risk of treatment.
Two invasive options are available for treating cerebral aneurysms, both of which carry some risk to the individual (such as possible damage to other blood vessels, the potential for aneurysm recurrence and rebleeding, and the risk of postoperative stroke). They include:
- Microvascular clipping — This procedure involves cutting off the flow of blood to the aneurysm. Under anesthesia, a section of the skull is removed and the aneurysm is located. The neurosurgeon uses a microscope to isolate the blood vessel that feeds the aneurysm and places a small, metal, clothespin-like clip on the aneurysm’s neck, halting its blood supply. The clip remains in the person and prevents the risk of future bleeding. Clipping has been shown to be highly effective, depending on the location, shape, and size of the aneurysm. In general, aneurysms that are completely clipped surgically do not return.
- Trapping — In this related procedure, the surgeon clamps off (occludes) the entire artery that leads to the aneurysm. This procedure is often performed when the aneurysm has damaged the artery. An occlusion is sometimes accompanied by a bypass, in which a small blood vessel is surgically grafted to the brain artery, rerouting the flow of blood away from the section of the damaged artery.
Endovascular embolization is an alternative to surgery. Once the individual has been anesthetized, the doctor inserts a hollow plastic tube (a catheter) into an artery (usually in the groin) and threads it, using fluoroscopic angiography, through the body to the site of the aneurysm. Using a guide wire, detachable coils (spirals of platinum wire) are passed through the catheter and released into the aneurysm. The coils fill the aneurysm, block it from circulation and cause the blood within the aneurysm sac to clot, which effectively destroys the aneurysm. The procedure may need to be performed more than once during the person’s lifetime.
Other treatments associated with the management of cerebral aneurysms that are symptomatic may include anticonvulsants to prevent seizures and analgesics to treat headache. Vasospasm can be treated with calcium channel-blocking drugs and sedatives may be ordered if the person is restless. A shunt may be surgically inserted into a ventricle at the time of the hemorrhage or up to several months following rupture if the buildup of cerebrospinal fluid is causing harmful pressure on surrounding tissue.
Individuals who have suffered a subarachnoid hemorrhage often need rehabilitative, speech and occupational therapy to regain lost function and learn to cope with any permanent disability.