The basilar artery is a major blood vessel at the base of the brain that supplies oxygen-rich blood to several structures. It is part of the brain’s posterior circulation, a network distinct from the anterior circulation supplied by the carotid arteries. Because the basilar artery provides blood to areas controlling fundamental bodily functions, any disruption to its flow can have widespread effects.
Anatomy of the Basilar Artery
The basilar artery is formed by the joining of the two vertebral arteries, which run up through the neck. These arteries converge at the junction between the pons and the medulla oblongata to form the single basilar artery. This artery then travels along a groove on the front surface of the pons, a part of the brainstem. The entire network, including the basilar artery and its branches, is referred to as the vertebrobasilar system.
This artery’s primary function is to deliver oxygenated blood to the posterior portions of the brain. It gives off several smaller branches that supply blood to the brainstem, which regulates autonomic functions like breathing and heart rate. It also supplies the cerebellum, the brain region responsible for coordinating voluntary movements, balance, and speech. The basilar artery ultimately divides to form the posterior cerebral arteries, which provide blood to the occipital lobes for processing visual information.
Conditions Affecting the Basilar Artery
Several medical conditions can compromise the structure and function of the basilar artery. One of the most common is atherosclerosis, where fatty deposits, or plaque, build up inside the artery walls. This buildup causes the artery to narrow (stenosis), restricting blood flow and reducing the blood supply to the posterior brain.
A basilar artery stroke occurs when blood flow through the artery is blocked. This blockage is often caused by a thrombus, a blood clot that forms on an atherosclerotic plaque within the artery. An embolus, a clot that travels from another part of the body, can also become lodged in the artery. In some cases, a tear in the artery wall, known as a dissection, can disrupt blood flow and cause a stroke.
Another condition is a basilar artery aneurysm, which is a weak, bulging spot in the artery wall. These aneurysms can pose a threat if they grow large enough to compress nearby nerves or if they rupture. A ruptured aneurysm causes a hemorrhagic stroke, leading to bleeding into the space surrounding the brain. Vertebrobasilar insufficiency describes reduced blood flow in the posterior circulation, which can result from stenosis and increases the risk for transient ischemic attacks (TIAs), or “mini-strokes.”
Symptoms of Basilar Artery Problems
The symptoms of basilar artery problems are varied and depend on the specific brain region affected by reduced blood flow. One of the most frequently reported symptoms is vertigo, a severe spinning sensation or dizziness that can make balance and walking difficult. This occurs because the basilar artery supplies the cerebellum and brainstem, which play a large part in maintaining equilibrium.
Visual disturbances are also a common indicator of a basilar artery issue, and can manifest as blurred vision, double vision (diplopia), or a sudden loss of sight. Speech can be affected, leading to slurred words (dysarthria) or difficulty articulating thoughts. Nausea and vomiting may also occur, often alongside other neurological symptoms.
Sudden weakness, numbness, or paralysis, particularly if it affects one or both sides of the body, can be a sign of a basilar artery stroke. A severe, sudden-onset headache, often described as the worst headache of one’s life, can be a symptom of a ruptured aneurysm. The abrupt appearance of any of these symptoms requires immediate medical evaluation to address disruptions in blood flow to the brain.
Diagnostic and Treatment Approaches
Physicians use advanced imaging to diagnose conditions related to the basilar artery. Diagnostic tools include:
- A computed tomography (CT) scan to quickly identify if a stroke is caused by a bleed (hemorrhagic).
- A CT angiogram (CTA) or magnetic resonance angiogram (MRA), which use contrast dye to highlight the arteries and reveal blockages, narrowing, or aneurysms.
- A catheter-based cerebral angiogram, which provides the most detailed images and may be used to confirm a diagnosis.
Treatment strategies are tailored to the specific condition. For an ischemic stroke caused by a blood clot, thrombolytic medications (“clot-busters”) may be administered intravenously to dissolve the clot. In some cases, a mechanical thrombectomy is performed, where a catheter is guided to the clot to physically remove it. For basilar artery stenosis, management involves medications like antiplatelet drugs and statins to manage cholesterol and prevent future clots.
For a basilar artery aneurysm, treatment focuses on preventing rupture. This can be achieved through endovascular coiling, a minimally invasive procedure where small coils are placed into the aneurysm to block blood flow into it. Another option is surgical clipping, where a surgeon places a small metal clip at the base of the aneurysm to seal it off. Lifestyle modifications, such as controlling blood pressure and quitting smoking, are also part of long-term management for all basilar artery conditions.