Intracranial vascular conditions involve the network of blood vessels within the skull that supply blood to the brain. This system, including arteries, veins, and capillaries, ensures the brain receives necessary oxygen and nutrients. Any disruption can have significant consequences for brain health.
Understanding Intracranial Blood Vessels
The brain relies on a constant supply of blood to operate effectively. Oxygenated blood travels from the heart to the brain through arteries, primarily the internal carotid and vertebral arteries. The internal carotid arteries supply the front two-thirds of the brain, branching into vessels like the anterior cerebral and middle cerebral arteries. The vertebral arteries, located in the back of the neck, merge to form the basilar artery, which supplies the rear portions of the brain.
These arteries divide into capillaries, tiny, thin-walled vessels where oxygen and nutrients are exchanged with brain tissue. After this exchange, deoxygenated blood and waste products are collected by venules, which drain into larger veins. These veins then lead to dural venous sinuses, such as the superior sagittal sinus and transverse sinuses, which return the blood to the heart.
Common Intracranial Vascular Conditions
Various conditions can affect the blood vessels inside the skull, impacting their structure and function. These conditions can disrupt normal blood flow, potentially leading to brain damage.
Intracranial aneurysms are bulges in a blood vessel, caused by a weakness in the vessel wall. These can occur anywhere in the brain but are frequently found in arteries at the base of the brain, particularly in the circle of Willis. An aneurysm can put pressure on brain tissue or nerves. If it ruptures, it can cause bleeding into the brain or surrounding area, known as a subarachnoid hemorrhage.
Arteriovenous malformations (AVMs) are abnormal tangles of blood vessels where arteries connect directly to veins, bypassing the usual network of capillaries. This direct connection means high-pressure arterial blood flows into veins not designed to handle such pressure, which can weaken the vessels. AVMs can occur in the brain or spinal cord and may lead to bleeding or damage to nearby tissues.
Ischemic stroke occurs when a blood vessel supplying the brain becomes blocked, depriving brain cells of oxygen. This blockage often happens due to a blood clot that forms in the brain (thrombotic stroke) or a clot that travels to the brain from another part of the body (embolic stroke). Atherosclerosis, a buildup of fatty deposits in the arteries, is a common underlying cause.
Hemorrhagic stroke involves bleeding into the brain due to a ruptured blood vessel. The bleeding disrupts normal circulation and increases pressure inside the skull, which can damage or kill brain cells. There are two main types: intracerebral hemorrhage, where bleeding occurs directly within the brain tissue, and subarachnoid hemorrhage, which is bleeding into the space between the brain and its outer protective covering.
Cavernous malformations, also known as cavernomas, are clusters of abnormally formed capillaries with weak walls. They are prone to leaking blood into the surrounding brain or spinal cord tissue, even if the bleeding is slow and low-pressure.
Recognizing the Signs
The signs and symptoms of an intracranial vascular issue can vary widely, depending on the specific condition, its size, and its location within the brain. However, certain general warning signs should prompt immediate medical attention.
A sudden, severe headache, often described as the “worst headache of your life” or a “thunderclap headache,” is a serious symptom, especially with conditions like a ruptured aneurysm or subarachnoid hemorrhage. Other sudden neurological changes can also indicate a problem. This includes sudden weakness or numbness on one side of the body, which might affect the face, arm, or leg.
Difficulty speaking or understanding speech, known as aphasia, can occur suddenly, as can changes in vision, such as blurred or double vision, or a loss of part of the visual field. Sudden dizziness, loss of balance, or problems with coordination are also symptoms. Nausea and vomiting, particularly when accompanied by a severe headache, can also be present. These symptoms warrant immediate emergency medical evaluation.
Diagnosing and Treating Intracranial Vascular Conditions
Diagnosing intracranial vascular conditions involves a combination of physical examination, medical history review, and specialized imaging tests. Computed tomography (CT) scans can visualize calcifications in arteries and detect acute bleeding in the brain. Magnetic resonance imaging (MRI) provides detailed images of brain tissue and can highlight blood vessels.
Angiography techniques are frequently used. CT angiography (CTA) and MR angiography (MRA) create high-resolution images of brain arteries, often with a contrast dye, to help diagnose conditions like aneurysms and arteriovenous malformations. Digital subtraction angiography (DSA) involves inserting a catheter into an artery and injecting contrast dye to obtain detailed X-ray images of the blood vessels.
Treatment approaches depend on the specific condition, its severity, and location. Medical management includes controlling blood pressure and administering medications, such as blood thinners, to prevent clots or manage symptoms. Endovascular procedures are minimally invasive techniques where catheters are guided through blood vessels to the affected area. For aneurysms, coiling involves placing tiny metal coils inside the bulge to block blood flow, while embolization for AVMs uses synthetic materials to prevent blood flow to the malformation.
Surgical intervention may be necessary for some conditions. Aneurysm clipping involves opening the skull and placing a small metal clip at the base of the aneurysm to seal it off. Surgical removal may also be an option for certain AVMs. Radiation therapy, such as stereotactic radiosurgery, uses focused radiation beams to shrink or close off abnormal blood vessels, particularly for AVMs.