Cerebral aneurysms are abnormal balloons or blisters on blood vessels supplying blood to the brain. Cerebral aneurysms are estimated to be present in about 5 percent of the general population; 20 percent of aneurysm patients may actually harbor multiple aneurysms.
The exact cause of a cerebral aneurysm is unknown. However, it appears that smoking and hypertension may be risk factors. We also know that aneurysms are more common in patients with certain genetic diseases, such as polycystic kidney disease, fibromuscular dysplasia, connective tissue disorders and coarctation of the aorta. In addition, aneurysms are associated with arteriovenous malformations (AVM) and moyamoya disease. For these reasons, many physicians recommend that patients with these disorders or with a family history of cerebral aneurysms undergo a non-invasive screening test, such as a magnetic resonance angiogram (MRA) or CT angiography (CTA).
Although in rare cases an aneurysm may reach a size where it causes pressure on the brain and mimics a tumor, the vast majority are silent lesions until they leak or rupture. When an aneurysm leaks, it results in blood accumulating in and around the brain. Called a subarachnoid hemorrhage, this condition can lead to other problems, such as hydrocephalus and/or vasospasm.
Rupture of an aneurysm is the most feared complication, as initial bleeding may be fatal. For this reason, the major focus of aneurysm treatment is to eliminate the aneurysm before it has a chance to burst. When this is not possible, occlusion (closure) of the aneurysm is usually performed immediately following initial hemorrhage in order to prevent recurrent bleeding.
The diagnosis of a cerebral aneurysm is usually made after the aneurysm leaks or ruptures. A CT scan typically confirms the brain hemorrhage, but rarely reveals the aneurysm itself. In addition, while MRAs and CTAs are excellent screening tests in patients with unruptured aneurysms, a cerebral angiogram is required to see the complete aneurysm and plan the appropriate treatment.
The two main methods of aneurysm treatment are microsurgery and endovascular surgery. Microsurgery is the well-established, "gold standard" treatment method. Microsurgical treatment for aneurysms involves a surgical procedure to expose the aneurysm using delicate instruments and high-powered magnification. Once the aneurysm has been located, a specialized metal (titanium) clip is placed across the neck (base) of the aneurysm. The clip stops blood from entering the aneurysm, thereby preventing it from bleeding. The microsurgical technique has a long history and is continually advancing. Long-term follow-up shows an excellent success rate in preventing recurrent bleeding. During endovascular surgery, a catheter is introduced into a patient's peripheral artery (usually in the groin), and navigated to the area where the aneurysm is located using an angiogram as a "road map". Once found, the aneurysm is filled from the inside with tiny platinum coils. These coils react with the surrounding blood, causing it to clot, and thereby destroying the aneurysm. Endovascular treatment for cerebral aneurysms is a promising new technique. However, its long-term effectiveness is not yet known. Aneurysm regrowth is possible, and some patients may require close follow-up or additional treatments.
Depending on the shape, size and location of the aneurysm, as well as the health and age of the patient, some aneurysms may not require treatment. Alternatively, some complex aneurysms may require a combination of microsurgery and endovascular surgery or other types of procedures. A treatment that is appropriate for one patient may not be appropriate for another. At Lahey Hospital & Medical Center, we have considerable experience and specialized training in evaluating patients for both microsurgical and endovascular aneurysm treatment. Patients are evaluated by a team of physicians well-versed in all aspects of aneurysm management, and a treatment plan is carefully tailored to the patient's individual needs. Carlos A David, MD is our director of cerebrovascular surgery, and with In Sup Choi, MD, of Interventional Neuroradiology, coordinates the multidisciplinary evaluation and treatment of patients with cerebral aneurysms.