Leading expert in cerebrovascular neurosurgery, Dr. Mika Niemela, MD, explains the pathophysiology and risk factors for brain aneurysm rupture. He details how inflammation weakens the aneurysm wall over time. Blood pressure then causes stress on this weakened area. Dr. Mika Niemela, MD, discusses key patient-specific risk factors like smoking, hypertension, and female gender. He emphasizes that even small aneurysms can rupture.
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Understanding Unruptured Brain Aneurysm Rupture Risk Factors and Causes
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- Prevalence of Unruptured Brain Aneurysms
- How a Brain Aneurysm Ruptures
- Major Risk Factors for Aneurysm Rupture
- Patient-Specific Risk Assessment
- The Role of Aneurysm Size in Rupture Risk
- Full Transcript
Prevalence of Unruptured Brain Aneurysms
Unruptured intracranial aneurysms are a common incidental finding. Dr. Mika Niemela, MD, states that between 2% to 6% of all people harbor an unruptured brain aneurysm. This high prevalence is partly due to the increased use of brain MRI scans for various medical reasons. The discovery of an aneurysm immediately raises critical questions about its rupture risk and the need for treatment.
How a Brain Aneurysm Ruptures
The rupture of a brain aneurysm is a biomechanical failure. Dr. Mika Niemela, MD, explains that aneurysms lack the essential, robust structure of a normal blood vessel wall. Over time, inflammatory processes occur inside the aneurysm sac. This inflammation leads to a pathological change called myo-intimal hyperplasia and subsequent wall degeneration.
The aneurysm wall becomes progressively weaker and thinner. Eventually, the wall can no longer withstand the constant stress from systemic blood pressure. This is the point at which the brain aneurysm bursts, causing a hemorrhagic stroke.
Major Risk Factors for Aneurysm Rupture
Certain factors significantly increase the probability of an aneurysm rupturing. During his discussion with Dr. Anton Titov, MD, Dr. Niemela highlighted the most critical modifiable and non-modifiable risk factors. The primary risk factors for brain aneurysm rupture are smoking and hypertension. These conditions contribute to the inflammatory and degenerative processes that weaken the aneurysm wall.
Female gender is another major non-modifiable risk factor. Women have a statistically higher risk of aneurysm formation and rupture compared to men. Understanding these factors is essential for stratifying a patient's overall risk.
Patient-Specific Risk Assessment
Rupture risk is not universal; it varies dramatically from one individual to another. Dr. Mika Niemela, MD, provides a clear contrast to illustrate this point. A 40-year-old man who is active, a non-smoker, and normotensive has a relatively low rupture risk profile. His lifestyle factors are protective.
Conversely, a 55-year-old woman with a history of hypertension and smoking carries a much higher inherent risk of aneurysm rupture. For this patient, the risk is elevated "regardless of the size of the brain aneurysm," as Dr. Niemela told Dr. Anton Titov, MD. This underscores the necessity of a personalized medical evaluation.
The Role of Aneurysm Size in Rupture Risk
While patient factors are crucial, the physical characteristics of the aneurysm itself are also vital. Dr. Anton Titov, MD, noted that aneurysm size matters a lot in the treatment decision calculus. Larger aneurysms generally pose a greater immediate threat of rupture due to the higher wall stress they experience.
However, Dr. Mika Niemela, MD, offers an important caveat. He states that "even smaller brain aneurysms can rupture, at least with time." This means that no aneurysm, regardless of its current size, can be considered completely safe without a thorough evaluation of all other risk factors.
Full Transcript
Dr. Anton Titov, MD: Unruptured brain aneurysms are found more often because brain MRIs are done for many reasons. Should unruptured brain aneurysm be treated? That depends on aneurysm location, size, and rupture risk.
Dr. Anton Titov, MD: Why do brain aneurysms rupture? What are the factors that determine the risk of rupture of any given brain aneurysm?
Dr. Mika Niemela, MD: The problem is that aneurysms miss an essential part of normal blood vessels in the brain. Brain aneurysms start to grow. The aneurysm's wall becomes degenerated because there are inflammatory processes inside the brain aneurysm.
Inflammation causes myo-intimal hyperplasia and degeneration. The wall of the aneurysm becomes weak. Then at some point, the wall of the brain aneurysm cannot hold the stress. Stress on the wall of the aneurysm comes from the blood pressure. Then the aneurysm bursts.
Dr. Anton Titov, MD: But obviously, not all brain aneurysms rupture. So it is very difficult to determine the reasons in any particular person for all the factors that cause a brain aneurysm to rupture.
Dr. Mika Niemela, MD: Yes, between 2% to 6% of all people harbor unruptured intracranial aneurysms. Not all brain aneurysms rupture. Rupture of an aneurysm depends on risk factors: smoking, hypertension, and female gender.
Sometimes there is a male who is 40 years old. He is otherwise active, doesn't smoke, and has no hypertension. His brain aneurysm rupture risk is different than that of another person. Another person is a 55-year-old woman with hypertension and smoking. She has a much higher risk of brain aneurysm rupture regardless of the size of the brain aneurysm.
Dr. Anton Titov, MD: Of course, brain aneurysm size matters a lot.
Dr. Mika Niemela, MD: But also many risk factors affect the risk of brain aneurysm rupture. Even smaller brain aneurysms can rupture, at least with time.