Types of Brain Aneurysm

Introduction

A brain aneurysm, also known as a cerebral or intracranial aneurysm, is a bulging, weakened area in the wall of an artery in the brain. This bulge forms as blood pushes against the weakened wall, often creating a balloon-like shape. If the aneurysm ruptures, it can cause life-threatening bleeding in the brain, known as a subarachnoid hemorrhage. While many aneurysms remain asymptomatic and are discovered incidentally, others can cause significant neurological problems depending on their size, location, and whether they bleed.

Brain aneurysms vary in shape, size, and position within the brain’s complex network of blood vessels. Understanding the different types of brain aneurysms is crucial not only for diagnosis but also for determining the most appropriate treatment approach. Each type carries distinct characteristics and risks, and the management strategies may differ accordingly.

The classification of brain aneurysms is typically based on their shape and form. Let’s explore the major types of brain aneurysms that healthcare professionals commonly encounter in clinical practice.

Types of Brain Aneurysm

1. Saccular Aneurysm :- The most common type of brain aneurysm is the saccular aneurysm, also known as a berry aneurysm. It is named for its round, berry-like appearance and typically forms at the junctions of arteries in the brain’s Circle of Willis a ring-like structure at the base of the brain where several major arteries meet. These aneurysms often have a narrow neck connecting the sac to the artery. Saccular aneurysms are responsible for the majority of spontaneous subarachnoid hemorrhages. They are most likely to rupture when they reach a size greater than 7 millimeters, although smaller aneurysms can rupture depending on their location and shape. Factors such as high blood pressure, smoking, and genetic predisposition can increase the risk of rupture. Clinically, saccular aneurysms may remain silent for years, but if they press against nearby nerves or rupture, they can cause sudden and severe symptoms such as a thunderclap headache, vision changes, neck stiffness, or loss of consciousness. Treatment options include endovascular coiling or surgical clipping to isolate the aneurysm and prevent rupture.
2. Fusiform Aneurysm :- Fusiform aneurysms are less common than saccular aneurysms and differ significantly in shape. Instead of forming a sac or pouch, fusiform aneurysms involve a circumferential widening of the artery itself. The entire wall of the blood vessel expands, creating a spindle-shaped or tubular dilation. These aneurysms do not have a distinct neck, which makes them more complex to treat surgically or endovascularly. Fusiform aneurysms most frequently occur in large arteries, such as the basilar artery or vertebral arteries in the back of the brain. They are often associated with conditions like atherosclerosis, where plaque buildup weakens the blood vessel wall. These aneurysms may grow slowly and compress adjacent brain structures over time, leading to symptoms such as cranial nerve palsies, dizziness, or balance issues. Because they are less prone to sudden rupture compared to saccular aneurysms, fusiform aneurysms are sometimes managed conservatively with regular imaging. However, large or symptomatic fusiform aneurysms may require advanced treatments such as flow-diverting stents or complex vascular bypass procedures. The decision to intervene depends on the size, location, symptoms, and rate of growth.
3. Mycotic Aneurysm :- Mycotic aneurysms are rare and arise from infections, typically bacterial in origin. They occur when an infectious agent weakens the blood vessel wall, leading to the formation of an aneurysm. These aneurysms can occur anywhere in the brain’s vascular system but are often seen in distal, smaller arteries. The term “mycotic” historically referred to fungal infections, but today it is used broadly to describe any infection-related aneurysm. These aneurysms are often a complication of infective endocarditis, where bacteria from the heart’s infected valves enter the bloodstream and seed in cerebral arteries. Unlike saccular or fusiform aneurysms, mycotic aneurysms tend to have irregular shapes and are more fragile due to their infected and inflamed walls. They carry a high risk of rupture and can result in severe brain hemorrhage, especially if left untreated. Management includes aggressive antibiotic therapy to treat the underlying infection, along with surgical or endovascular intervention in selected cases. Timely identification is critical, as mycotic aneurysms can deteriorate rapidly. Diagnosis is typically confirmed with imaging studies and blood cultures, especially in patients with known infections or recent cardiac procedures.
4. Dissecting Aneurysm :- A dissecting aneurysm occurs when there is a tear in the inner lining of a cerebral artery, allowing blood to enter the vessel wall and create a false lumen. This condition can result in either narrowing of the artery or a ballooning out of the outer wall, leading to an aneurysmal formation. Dissecting aneurysms are often associated with trauma, connective tissue disorders like Marfan syndrome, or spontaneous dissection. They are more common in younger individuals and typically affect arteries such as the vertebral or carotid arteries. Symptoms of a dissecting aneurysm depend on the vessel involved and may include headache, neck pain, neurological deficits, or stroke. The rupture of a dissecting aneurysm can lead to subarachnoid or intracerebral hemorrhage, which can be life-threatening. Diagnosis is usually confirmed with CT angiography or MR angiography. Treatment depends on the severity and may include blood pressure control, antiplatelet therapy, or endovascular stenting to reinforce the vessel wall. In cases of rupture or severe narrowing, surgical intervention may be necessary.

Conclusion

Brain aneurysms are complex vascular abnormalities with significant variability in their form, cause, and clinical implications. The classification into saccular, fusiform, mycotic, and dissecting types provides a framework for understanding their pathophysiology, presentation, and treatment options. Each type presents unique challenges and requires a tailored approach based on the aneurysm’s location, size, and behavior.

Early detection of aneurysms, whether incidentally during imaging or through symptoms, is critical to preventing catastrophic complications such as rupture and hemorrhagic stroke. Advances in neuroimaging and endovascular techniques have greatly improved outcomes for patients with brain aneurysms. However, accurate diagnosis and timely management remain essential to ensuring long-term health and minimizing neurological damage.

By understanding the types of brain aneurysms, patients and healthcare providers can work together to develop individualized care plans that prioritize safety, monitor risk, and prevent life-threatening events.