Medically reviewed by Edward Tavel, MD, Medical Director · Last reviewed 22 August 2026
An aneurysm is a bulge that forms in the wall of a blood vessel where that wall has become weakened. Blood pressure pushes outward against the weak section, and over time the bulge can slowly enlarge. Aneurysms can develop in many vessels, but two locations account for most of the clinical attention they receive: the aorta, the large vessel carrying blood from the heart through the chest and abdomen, and the arteries at the base of the brain. Aneurysms are more common than many people expect. A meaningful share of adults carry a small brain aneurysm without ever knowing, and the majority of those never cause a problem during a person’s lifetime.
Most aneurysms produce no symptoms while they remain small and intact, which is why they are so often discovered incidentally during imaging performed for another reason. Larger ones can press on nearby structures and cause symptoms depending on location — a large abdominal aortic aneurysm may produce a pulsing sensation or deep back or abdominal discomfort, while a brain aneurysm pressing on a nerve can affect vision or eye movement. The concern with any aneurysm is rupture, which is uncommon but serious. A sudden, severe headache unlike any you have experienced before, or sudden severe chest, back, or abdominal pain, requires emergency care — call 911. Risk factors include high blood pressure, smoking, older age, and a family history of aneurysm, and smoking and blood pressure are the two most modifiable of these.
Because aneurysms are usually silent, imaging is the main way they are identified before they cause trouble. MRI and MR angiography can visualise blood vessels without ionizing radiation and, in many cases, without contrast dye, which makes them well suited to assessing vessels in people who have no symptoms. What matters most once an aneurysm is found is its size, location, and whether it changes over time, so many are simply monitored with repeat imaging at intervals rather than treated immediately. That decision belongs with your physician and, where relevant, a vascular or neurosurgical specialist. You can read more specifically about aortic aneurysms and what imaging shows, about what a cerebral aneurysm finding on a brain MRI really means, or about incidental findings on an MRI more generally.
Frequently asked questions
Does finding an aneurysm mean I need surgery?
Usually not. Many aneurysms are small and are managed by monitoring them with repeat imaging and by controlling blood pressure. Treatment is considered when size, location, growth rate, or other individual factors suggest it would be beneficial.
Can an aneurysm be felt or noticed?
Most cannot. Small aneurysms produce no sensation at all. Larger abdominal ones occasionally cause a noticeable pulsing feeling, and brain aneurysms pressing on a nerve can affect vision, but silence is the norm.
Are aneurysms hereditary?
Family history does raise risk, particularly where a first-degree relative has had one. If two or more close relatives have had a brain aneurysm, it is worth discussing screening with your physician, since guidance differs for that group.
Can MRI find aneurysms without contrast dye?
In many cases yes. MR angiography techniques can image flowing blood using the motion of the blood itself rather than an injected agent, which is one reason MRI is useful for assessing vessels in people without symptoms.
What actually lowers the risk of rupture?
Not smoking and keeping blood pressure well controlled are the two changes with the clearest benefit. Both are managed with your physician, and both matter more than any single imaging result.
Sources
A whole-body MRI at MRI Wellness looks at the brain, spine, chest, abdomen and pelvis in a single session, without radiation or contrast dye. No referral is needed.
