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Intracranial Aneurysm

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Description: An intracranial aneurysm is an abnormal bulging or ballooning of a blood vessel in the brain that can lead to life-threatening bleeding if it ruptures.
Type: Intracranial aneurysms are typically classified as saccular (berry) aneurysms, fusiform aneurysms, or dissecting aneurysms, based on their shape.

Regarding genetic transmission, intracranial aneurysms can have a hereditary component. The condition does not follow a clear Mendelian inheritance pattern, but familial predisposition has been observed, suggesting a complex, multifactorial inheritance involving both genetic and environmental factors. Familial clustering implies that individuals with a family history of intracranial aneurysms may have a higher risk of developing the condition.
Signs And Symptoms: A small, unchanging aneurysm will produce few, if any, symptoms. Before a larger aneurysm ruptures, the individual may experience such symptoms as a sudden and unusually severe headache, nausea, vision impairment, vomiting, and loss of consciousness, or no symptoms at all.
Prognosis: Outcomes depend on the size of the aneurysm. Small aneurysms (less than 7 mm) have a low risk of rupture and increase in size slowly. The risk of rupture is less than one percent for aneurysms of this size.The prognosis for a ruptured cerebral aneurysm depends on the extent and location of the aneurysm, the person's age, general health, and neurological condition. Some individuals with a ruptured cerebral aneurysm die from the initial bleeding. Other individuals with cerebral aneurysm recover with little or no neurological deficit. The most significant factors in determining outcome are the Hunt and Hess grade, and age. Generally patients with Hunt and Hess grade I and II hemorrhage on admission to the emergency room and patients who are younger within the typical age range of vulnerability can anticipate a good outcome, without death or permanent disability. Older patients and those with poorer Hunt and Hess grades on admission have a poor prognosis. Generally, about two-thirds of patients have a poor outcome, death, or permanent disability.Increased availability and greater access to medical imaging has caused a rising number of asymptomatic, unruptured cerebral aneurysms to be discovered incidentally during medical imaging investigations. Unruptured aneurysms may be managed by endovascular clipping or stenting. For those subjects that underwent follow-up for the unruptured aneurysm, computed tomography angiography (CTA) or magnetic resonance angiography (MRA) of the brain can be done yearly. Recently, an increasing number of aneurysm features have been evaluated in their ability to predict aneurysm rupture status, including aneurysm height, aspect ratio, height-to-width ratio, inflow angle, deviations from ideal spherical or elliptical forms, and radiomics morphological features.
Onset: Intracranial aneurysms often develop gradually over time and may go unnoticed until they rupture. The exact onset can vary and is generally asymptomatic until rupture occurs. Risk factors include high blood pressure, smoking, family history, and certain genetic conditions.
Prevalence: The prevalence of intracranial aneurysms is estimated to be around 2-5% in the general population. Most aneurysms remain asymptomatic and undiagnosed unless they rupture, leading to subarachnoid hemorrhage.
Epidemiology: The prevalence of intracranial aneurysm is about 1–5% (10 million to 12 million persons in the United States) and the incidence is 1 per 10,000 persons per year in the United States (approximately 27,000), with 30- to 60-year-olds being the age group most affected. Intracranial aneurysms occur more in women, by a ratio of 3 to 2, and are rarely seen in pediatric populations.
Intractability: An intracranial aneurysm itself is not necessarily intractable. Many cases can be managed or treated successfully, especially when detected early. Treatment options may include surgical procedures such as clipping or endovascular techniques like coiling to prevent rupture. However, if an aneurysm ruptures, it can lead to a subarachnoid hemorrhage, which is a serious medical emergency with potentially severe complications and higher intractability. The outcomes depend on factors like the size, location of the aneurysm, and timely medical intervention.
Disease Severity: Intracranial aneurysms can vary in severity. Small, unruptured aneurysms may be asymptomatic and pose minimal risk initially. However, larger aneurysms or those that rupture can be life-threatening, leading to severe complications such as subarachnoid hemorrhage, stroke, brain damage, or death. The severity largely depends on factors like the aneurysm's size, location, and whether it has ruptured.
Healthcare Professionals: Disease Ontology ID - DOID:10941
Pathophysiology: Aneurysm means an outpouching of a blood vessel wall that is filled with blood. Aneurysms occur at a point of weakness in the vessel wall. This can be because of acquired disease or hereditary factors. The repeated trauma of blood flow against the vessel wall presses against the point of weakness and causes the aneurysm to enlarge. As described by the law of Young-Laplace, the increasing area increases tension against the aneurysmal walls, leading to enlargement. In addition, a combination of computational fluid dynamics and morphological indices have been proposed as reliable predictors of cerebral aneurysm rupture.Both high and low wall shear stress of flowing blood can cause aneurysm and rupture. However, the mechanism of action is still unknown. It is speculated that low shear stress causes growth and rupture of large aneurysms through inflammatory response while high shear stress causes growth and rupture of small aneurysm through mural response (response from the blood vessel wall). Other risk factors that contributes to the formation of aneurysm are: cigarette smoking, hypertension, female gender, family history of cerebral aneurysm, infection, and trauma. Damage to structural integrity of the arterial wall by shear stress causes an inflammatory response with the recruitment of T cells, macrophages, and mast cells. The inflammatory mediators are: interleukin 1 beta, interleukin 6, tumor necrosis factor alpha (TNF alpha), MMP1, MMP2, MMP9, prostaglandin E2, complement system, reactive oxygen species (ROS), and angiotensin II. However, smooth muscle cells from the tunica media layer of the artery moved into the tunica intima, where the function of the smooth muscle cells changed from contractile function into pro-inflammatory function. This causes the fibrosis of the arterial wall, with reduction of number of smooth muscle cells, abnormal collagen synthesis, resulting in a thinning of the arterial wall and the formation of aneurysm and rupture. No specific gene loci has been identified to be associated with cerebral aneurysms.Generally, aneurysms larger than 7 mm in diameter should be treated because they are prone for rupture. Meanwhile, aneurysms less than 7 mm arise from the anterior and posterior communicating artery and are more easily ruptured when compared to aneurysms arising from other locations.
Carrier Status: Carrier status is not applicable to an intracranial aneurysm, as it is not an inherited condition in a manner similar to genetic carrier diseases. Instead, it is a localized dilation of a blood vessel in the brain due to a weakening of the vessel wall. Risk factors include hypertension, smoking, and family history.
Mechanism: An intracranial aneurysm is a dilation or ballooning of an artery within the brain due to weakening of the arterial wall. Here is an overview of its mechanism and molecular mechanisms:

**Mechanism:**
1. **Arterial Wall Weakening**: This occurs due to a combination of genetic factors, hemodynamic stress, and degenerative changes in the vessel wall.
2. **Hemodynamic Stress**: Blood flow can exert varying degrees of pressure on arterial walls, particularly at bifurcations (branch points) in the arteries, leading to their weakening and bulging.
3. **Formation and Rupture**: Over time, the weakened section can expand and form a balloon-like sac. If the aneurysm continues to enlarge, the wall can become increasingly thin and risk rupturing, leading to a hemorrhagic stroke.

**Molecular Mechanisms:**
1. **Extracellular Matrix (ECM) Degradation**: Enzymes like matrix metalloproteinases (MMPs) break down components of the ECM, undermining its structural integrity.
2. **Vascular Smooth Muscle Cell (VSMC) Apoptosis**: The loss of VSMCs, which provide strength and contractility to the vascular wall, can lead to fragility and dilation of the vessel.
3. **Inflammation**: Inflammatory cells such as macrophages and T-cells infiltrate the arterial wall, releasing cytokines and proteolytic enzymes that further degrade the ECM and promote VSMC apoptosis.
4. **Genetic Factors**: Mutations or variations in genes related to the ECM (e.g., COL1A2, COL3A1), inflammatory processes, and VSMC function may predispose individuals to intracranial aneurysms.
5. **Endothelial Dysfunction**: Damage to endothelial cells lining the blood vessels can impair the regulation of vascular tone and integrity, contributing to aneurysm development.

These molecular and cellular processes interplay to weaken the arterial wall and contribute to the formation and potential rupture of intracranial aneurysms.
Treatment: Emergency treatment for individuals with a ruptured cerebral aneurysm generally includes restoring deteriorating respiration and reducing intracranial pressure. Currently there are two treatment options for securing intracranial aneurysms: surgical clipping or endovascular coiling. If possible, either surgical clipping or endovascular coiling is typically performed within the first 24 hours after bleeding to occlude the ruptured aneurysm and reduce the risk of recurrent hemorrhage.While a large meta-analysis found the outcomes and risks of surgical clipping and endovascular coiling to be statistically similar, no consensus has been reached. In particular, the large randomised control trial International Subarachnoid Aneurysm Trial appears to indicate a higher rate of recurrence when intracerebral aneurysms are treated using endovascular coiling. Analysis of data from this trial has indicated a 7% lower eight-year mortality rate with coiling, a high rate of aneurysm recurrence in aneurysms treated with coiling—from 28.6 to 33.6% within a year, a 6.9 times greater rate of late retreatment for coiled aneurysms, and a rate of rebleeding 8 times higher than surgically clipped aneurysms.
Compassionate Use Treatment: Compassionate use treatment for intracranial aneurysm might involve access to investigational therapies or devices that are still in clinical trials but show potential to benefit patients with limited treatment options. This could include novel endovascular tools or drugs designed to enhance the healing process post-intervention.

Off-label or experimental treatments for intracranial aneurysms typically involve the use of medications or techniques not yet formally approved for this specific condition. Examples could include:

1. **Flow diversion devices**: Originally approved for certain types of aneurysms, these stents can be used off-label for other aneurysm locations or types.
2. **Pipeline Embolization Device (PED)**: This device is used in large or giant wide-neck aneurysms, sometimes off-label in smaller aneurysms.
3. **Pharmaceuticals**: Some anti-inflammatory or neuroprotective drugs may be used off-label to manage aneurysm-related symptoms or complications.
4. **Gene Therapy**: Experimental approaches like gene therapy to stabilize the vessel wall could be explored.

These treatments should always be considered and applied by a specialist familiar with the current evidence and regulatory environment.
Lifestyle Recommendations: Lifestyle recommendations for managing and potentially reducing the risk of an intracranial aneurysm include:

1. **Control Blood Pressure:** Maintain a healthy blood pressure through regular monitoring and prescribed medications if necessary.
2. **Quit Smoking:** Avoid tobacco products, as smoking increases the risk of aneurysms.
3. **Limit Alcohol Consumption:** Drink alcohol in moderation, as excessive drinking can elevate blood pressure.
4. **Healthy Diet:** Consume a balanced diet rich in fruits, vegetables, lean proteins, and whole grains to support overall cardiovascular health.
5. **Regular Exercise:** Engage in regular physical activity to maintain cardiovascular health and control blood pressure.
6. **Stress Management:** Practice stress-reduction techniques such as yoga, meditation, or deep-breathing exercises.
7. **Avoid Stimulants:** Refrain from using stimulant drugs, which can elevate blood pressure and increase aneurysm risk.
8. **Monitor Cholesterol Levels:** Keep cholesterol levels in check with diet, exercise, and medications if prescribed.
9. **Regular Health Check-ups:** Have routine medical check-ups for the early detection and management of risk factors.

These lifestyle changes can help manage existing aneurysms and reduce the risk of complications.
Medication: For managing intracranial aneurysms, medications are typically aimed at controlling symptoms and preventing complications. These may include:

1. **Antihypertensives**: To control high blood pressure, which can reduce the risk of aneurysm rupture.
2. **Calcium channel blockers**: Such as nimodipine, may be used to prevent cerebral vasospasm, particularly after a subarachnoid hemorrhage.
3. **Analgesics**: For pain relief if the patient is experiencing headaches or other pain.
4. **Anticonvulsants**: To prevent seizures that can result from an aneurysm or its treatment.

Medications will not eliminate the aneurysm but can help manage associated risks and symptoms.
Repurposable Drugs: Currently, there are no widely accepted repurposable drugs specifically indicated for the treatment of intracranial aneurysms. Treatment typically involves surgical interventions, such as clipping or endovascular coiling, to prevent rupture. Medications may be used to manage related symptoms or conditions, such as antihypertensives for blood pressure control. Research may be ongoing in this area, so consulting current clinical trials or medical literature could provide the latest information.
Metabolites: Intracranial aneurysms are localized dilations of blood vessels within the brain due to weakened arterial walls. Metabolites specifically associated with intracranial aneurysms have not been well-characterized. However, metabolic factors such as oxidative stress and inflammatory mediators may play roles in the pathogenesis and progression of aneurysms. Further research is needed to identify and understand the specific metabolites involved. If you have any other questions or need additional information, feel free to ask.
Nutraceuticals: Nutraceuticals are food-derived products that offer health benefits, including the potential prevention and treatment of disease. For intracranial aneurysms, there is limited evidence on the direct impact of specific nutraceuticals. However, maintaining overall vascular health through a balanced diet rich in omega-3 fatty acids, antioxidants (e.g., vitamins C and E), and folate might support blood vessel integrity and reduce the risk factors associated with aneurysm formation. Always consult with a healthcare professional before starting any new supplement regimen.
Peptides: There is no well-established direct connection between peptides and the treatment or cause of intracranial aneurysms. Current management of intracranial aneurysms typically involves medical imaging for diagnosis and surgical interventions like clipping or endovascular coiling for treatment. Research into the use of peptides or nanotechnology for intracranial aneurysms could be ongoing, but it remains outside the standard clinical practice as of now.