An aneurysm is a bulge or ballooning that forms in the wall of a blood vessel due to weakening of the artery wall. This structural failure cannot withstand the constant pressure of blood flow, causing the vessel to swell outward. True aneurysms typically do not correct themselves, meaning medical intervention is almost always necessary to prevent catastrophic outcomes.
Understanding Aneurysms and Their Types
Aneurysms are classified based on their location and shape, with the most common types occurring in the brain and the aorta. Cerebral aneurysms affect arteries within the brain and are the most common type to cause a severe event upon rupture. Abdominal aortic aneurysms (AAAs) and thoracic aortic aneurysms (TAAs) form in the aorta, the body’s main artery that carries blood from the heart.
Aneurysms are also distinguished by shape. A saccular aneurysm, or berry aneurysm, is the most common type of cerebral aneurysm, appearing as a rounded sac attached to the side of the artery. A fusiform aneurysm involves a uniform dilation that bulges out on all sides. A true aneurysm involves all three layers of the arterial wall, while a pseudoaneurysm is a contained leak held by surrounding tissue, lacking one or more vessel wall layers.
Spontaneous Resolution: A Medical Reality Check
The hope that a true aneurysm will spontaneously disappear is largely unfounded in medical practice. The structural damage that allowed the vessel to balloon outward remains, meaning the problem persists and may progress. The natural history of most true aneurysms is either to remain stable or to slowly grow larger over time.
Rare reports of spontaneous resolution exist, but this phenomenon is almost exclusively limited to pseudoaneurysms. A pseudoaneurysm, which is a contained hematoma outside the arterial wall, can sometimes clot off on its own, a process called spontaneous thrombosis. This spontaneous closure is occasionally observed in smaller pseudoaneurysms, such as those that form after an arterial puncture. Relying on this improbable outcome for a true cerebral or aortic aneurysm is a dangerous strategy given the inherent risk of rupture.
The Risk of Rupture and Warning Symptoms
Because a true aneurysm does not resolve on its own, the primary danger is that the weakened wall will eventually tear, leading to rupture and hemorrhage. A ruptured cerebral aneurysm causes bleeding into the space surrounding the brain, known as a subarachnoid hemorrhage, which is a medical emergency. Ruptured brain aneurysms are fatal in about 50% of cases, and many survivors experience permanent neurological deficits.
The most common warning symptom of a ruptured cerebral aneurysm is a sudden, explosive headache, often described as the “worst headache of one’s life.” This severe pain is frequently accompanied by symptoms such as nausea, vomiting, a stiff neck, and light sensitivity. Rupture of an abdominal aortic aneurysm can present as sudden, intense pain in the chest, abdomen, or back, often described as a tearing sensation. Immediate emergency medical attention is necessary if any of these acute symptoms appear, as up to 50% of patients with a ruptured aortic aneurysm may die before reaching the hospital.
Medical Management and Treatment Options
Since spontaneous resolution is not a reliable expectation for true aneurysms, medical management follows two main paths: monitoring or active intervention. For small, asymptomatic aneurysms, particularly those under 7 millimeters, a period of watchful waiting may be recommended. This approach involves closely monitoring the aneurysm size and shape with regular imaging scans, while aggressively managing risk factors like high blood pressure and smoking. The decision to monitor versus treat is based on the aneurysm’s size, location, the patient’s age, and their overall health.
Active intervention is pursued when the risk of rupture outweighs the risk of the procedure itself. Two primary methods exist for treating cerebral aneurysms: surgical clipping and endovascular coiling. Surgical clipping is an open-surgery procedure where a neurosurgeon places a small metal clip across the aneurysm’s neck to seal it off from blood flow. Endovascular coiling is a less invasive technique where a catheter is threaded to the aneurysm, and tiny platinum coils are deployed inside to induce clotting. The choice between clipping and coiling depends on the aneurysm’s characteristics and the patient’s condition.