An aneurysm is an outpouching or sac that arises from an artery around the brain. The aneurysm grows from a patch in the wall of an artery that has a weakness in its middle layer. Although patients with aneurysms are born with a weakness in one or more spots of the arteries in the brain, it takes many years for aneurysms to grow. An aneurysm grows because the pounding of the blood in this weak spot expands the sac.
If the expansion of the aneurysm reaches a point where the wall becomes very thin, it ruptures and bleeds into the space around the brain. This event is called a subarachnoid hemorrhage. This catastrophic event requires immediate and urgent medical attention. After the first hemorrhage, about 46 percent of patients die. If the aneurysm is not repaired in time and a second hemorrhage occurs, about 80 percent of patients die.
Johns Hopkins estimates that two percent of people have one or more brain aneurysms. Most aneurysms declare themselves by bleeding in adults between the ages of 45 to 65 years. Children, however, can also present with aneurysms. Two-to-three percent of patients with aneurysms that we treat at Johns Hopkins are children. We attempt whenever possible to identify and eliminate aneurysms before they bleed. We typically find the aneurysm in a computed tomography (CT) scan or, more commonly, in a magnetic resonance angiography(MRA) scan. If we find an aneurysm by CT or MRA, we then obtain an angiogram. An angiogram (also called arteriogram) is a special test in which a neuroradiologist injects dye into the blood vessels in the brain and obtains images of the blood vessels. At this point, the angiogram is the test that most accurately shows the aneurysm and its relationship to the surrounding arteries and veins.
At Johns Hopkins, we treat aneurysms using one of two methods, depending on the type of aneurysm:
Microsurgical clipping – the more established of the two techniques. During microsurgical clipping, we perform a craniotomy and using the microscope occlude the base of the aneurysm with a specialized clip, thus preserving flow in the artery from which the aneurysm arises. The first aneurysm ever treated by surgical clipping was operated on at Johns Hopkins by Dr. Walter Dandy on March 23, 1937.
Endovascular coiling – a more recent treatment for aneurysms. It has been used in patients since 1991. During endovascular coiling, we pass a catheter through the groin up into the artery containing the aneurysm and release platinum coils. The coils induce clotting of the aneurysm and in this way prevent blood from getting into it.
The cerebrovascular team at Johns Hopkins evaluates each aneurysm patient to decide the best singular therapy or combination of treatments for their specific case. Johns Hopkins is one of the few hospitals in the country that treats more than 100 aneurysm cases a year. We have published our aneurysm treatment results, which rank among the best in the world.