An aneurysm is a localized bulge or ballooning in a weakened area of a blood vessel wall. When this occurs in the brain, it is called a cerebral or intracranial aneurysm. The basilar artery, located at the base of the brain, supplies blood to various brain structures. Aneurysms in this location can have severe consequences.
Understanding Basilar Artery Aneurysms
The basilar artery forms at the front of the brainstem from two vertebral arteries. It is the main vessel supplying oxygen-rich blood to the posterior portion of the brain, including the brainstem, cerebellum, and parts of the posterior cerebral hemispheres. The brainstem controls basic bodily functions such as breathing and heart rate, while the cerebellum manages voluntary movements, balance, and speech. It also gives off numerous smaller branches that supply the pons and midbrain.
A basilar artery aneurysm is a weakened, bulging spot in the wall of this artery. The constant pressure of blood flow against the weakened vessel wall can cause this area to expand over time. Its location deep within the brain, surrounded by delicate and functionally dense structures, means that even a small aneurysm can exert pressure on these areas, and a rupture can have devastating effects.
Aneurysms can present in different forms. The most common are saccular, also known as “berry” aneurysms, which appear as a rounded sac extending from the side of the artery. Another type is fusiform, where the artery wall bulges out on all sides in a spindle shape. Some aneurysms can also be dissecting, forming when a tear in the inner layer of the artery wall allows blood to flow between the layers, creating a bulge.
Several factors can contribute to basilar artery aneurysms. High blood pressure is a common risk factor, increasing stress on arterial walls. Smoking also weakens blood vessel walls, raising the risk of aneurysm formation. A family history of aneurysms or certain genetic conditions, such as Ehlers-Danlos syndrome or polycystic kidney disease, can also predispose individuals to these weaknesses.
Recognizing the Symptoms
Many basilar artery aneurysms do not cause noticeable symptoms until they become large or rupture. Small, unruptured aneurysms are often discovered incidentally during imaging for other medical conditions. If an unruptured aneurysm grows large enough, it can press on nearby brain structures or nerves, leading to symptoms.
Symptoms of an unruptured basilar artery aneurysm can include headaches, sometimes localized behind the eye. Vision problems such as double vision or a drooping eyelid can occur if the aneurysm affects cranial nerves controlling eye movement. Individuals might also experience balance issues, facial numbness, or weakness on one side of the face.
A ruptured basilar artery aneurysm is a medical emergency with sudden and severe symptoms. The most prominent symptom is an abrupt, excruciating headache, often described as the “worst headache of your life” or a “thunderclap headache.” This intense pain can be accompanied by a stiff neck, nausea, and vomiting. Sensitivity to light, loss of consciousness, or sudden neurological deficits resembling a stroke, such as weakness or difficulty speaking, also indicate a ruptured aneurysm.
Detecting Basilar Artery Aneurysms
The detection of basilar artery aneurysms often occurs by chance during brain imaging performed for unrelated reasons or after a rupture. When symptoms suggest a possible aneurysm, or if a rupture is suspected, specific imaging techniques are used to confirm the diagnosis and provide detailed information.
One common diagnostic tool is Computed Tomography Angiography (CTA), which uses X-rays and an injected contrast dye to generate detailed images of blood vessels in the brain. This allows medical professionals to visualize arteries and identify any bulges. Magnetic Resonance Angiography (MRA) is another imaging technique that uses magnetic fields and radio waves to create detailed images of blood vessels, providing a non-invasive way to detect aneurysms without using radiation.
For the most precise and detailed visualization, cerebral angiography, also known as Digital Subtraction Angiography (DSA), is used. This procedure involves inserting a thin, flexible tube (catheter) into an artery, usually in the groin, and guiding it up to the brain’s blood vessels. A contrast dye is then injected, and X-ray images are taken to produce highly accurate pictures of the aneurysm’s size, shape, and exact location, which is crucial for treatment planning.
Treatment Options and Specialized Care
Decisions regarding basilar artery aneurysm treatment are intricate, considering factors like the aneurysm’s size, shape, precise location, patient’s age, overall health, and whether it has ruptured. For very small, unruptured aneurysms, watchful waiting with regular monitoring may be recommended to observe for changes.
One common minimally invasive procedure is endovascular coiling. A catheter is guided from an artery in the groin to the aneurysm in the brain. Tiny platinum coils are then deployed into the aneurysm, filling the sac and blocking blood flow. This promotes the formation of a clot within the aneurysm, effectively sealing it off from the main artery and reducing the risk of rupture.
Alternatively, surgical clipping is an open-brain procedure. A neurosurgeon makes an incision in the skull to access the aneurysm. A small, metal clip is then placed at the base, or “neck,” of the aneurysm to seal it off from blood circulation. This method isolates the aneurysm, preventing blood from entering it. However, due to the basilar artery’s deep and delicate location within the brain, surgical clipping for these aneurysms can be complex.
Newer approaches include flow diversion devices, which are stents placed within the parent artery across the aneurysm opening. These devices work by diverting blood flow away from the aneurysm over time, rather than immediately blocking it. This reduced blood flow encourages the aneurysm to clot and shrink, eventually leading to its obliteration.
Treating basilar artery aneurysms is challenging due to their location at the brainstem, often involving complex anatomy such as a broad neck or the involvement of small, perforating branches. These complexities can make precise intervention difficult and contribute to an unpredictable recovery. Management requires highly specialized neurosurgical and neurointerventional teams with extensive experience.