Atherosclerosis, or “hardening of the arteries,” is a condition where plaque buildup narrows and stiffens blood vessels. While often linked to heart disease, this process can also affect the arteries supplying blood to the brain, a condition known as intracranial atherosclerosis. The gradual narrowing of these cerebral arteries impedes blood flow and can lead to significant neurological problems.
Plaque Formation in Cerebral Arteries
The development of atherosclerosis in the brain’s arteries begins with an injury to the endothelium, the vessel’s inner lining. This damage, caused by factors like high blood pressure or toxins from smoking, makes the artery wall permeable. This allows low-density lipoprotein (LDL) cholesterol to seep from the bloodstream into the arterial wall, where it undergoes oxidation and triggers an inflammatory response.
The immune system reacts by sending white blood cells called monocytes to the site. These monocytes cross the endothelium and transform into macrophages, which consume the oxidized LDL. As macrophages become engorged with cholesterol, they turn into “foam cells,” a primary component of early atherosclerotic plaque.
Over time, these foam cells accumulate within the artery wall. Smooth muscle cells migrate to the surface of this deposit and produce fibrous connective tissue, forming a hard cap over the plaque. This plaque, which contains a core of foam cells and lipids, narrows the artery, reduces its flexibility, and can become unstable enough to rupture.
Neurological Consequences
Plaque in cerebral arteries can disrupt blood flow and lead to severe neurological events. An ischemic stroke occurs when the blood supply to a part of the brain is suddenly cut off, causing brain cells to die. A Transient Ischemic Attack (TIA) is similar, but the blockage is temporary and symptoms resolve without permanent brain damage.
These events can happen when a plaque ruptures, triggering the formation of a blood clot (thrombus) on its surface. This clot can grow and obstruct the artery, or a piece can break off and lodge in a smaller artery downstream. The symptoms of a stroke or TIA appear suddenly and may include numbness, weakness in the limbs, difficulty speaking, or vision problems.
Beyond acute events, intracranial atherosclerosis has chronic effects. The long-term reduction of blood flow, or hypoperfusion, deprives the brain of needed oxygen and nutrients. This can lead to a progressive decline in cognitive abilities known as vascular cognitive impairment.
Symptoms of this impairment may include memory loss, confusion, and difficulty with problem-solving. Over time, this condition can progress to vascular dementia.
Key Risk Factors and Causes
The risk of developing atherosclerosis in the brain is influenced by a combination of manageable and unchangeable factors. Non-modifiable risk factors include advancing age and a person’s genetic background or family history.
Modifiable risk factors are related to lifestyle and health conditions that can be controlled. High blood pressure (hypertension) is a contributor, as it damages the endothelial lining of arteries. High levels of LDL cholesterol and other fats (hyperlipidemia) provide the material for plaque, while diabetes mellitus also increases risk.
Behaviors such as smoking are damaging because the chemicals injure artery walls and promote inflammation. Obesity and a sedentary lifestyle are also contributors. These factors often worsen other modifiable risks like high blood pressure and unhealthy cholesterol levels, accelerating arterial damage.
Diagnosis and Medical Evaluation
Diagnosing atherosclerosis in the brain begins with a medical evaluation of a patient’s symptoms, medical history, and risk factors. If the condition is suspected, non-invasive imaging tests are used to visualize the cerebral arteries and assess blood flow.
Magnetic Resonance Angiography (MRA) and Computed Tomography Angiography (CTA) are two common techniques. MRA uses magnets and radio waves to create arterial images, while CTA uses X-rays and a contrast dye to highlight the vessels. Both can detect areas of narrowing or blockage in the cerebral arteries.
Another tool is the Transcranial Doppler (TCD) ultrasound, which uses sound waves to measure blood flow speed and identify blockages. In some cases, a more definitive invasive procedure called cerebral angiography may be performed. This test uses a catheter and contrast dye to create a highly detailed map of the brain’s arteries, allowing for precise measurement of stenosis.
Treatment and Management Strategies
Managing intracranial atherosclerosis focuses on slowing disease progression and preventing complications like stroke. The first line of defense involves lifestyle modifications. Adopting a diet low in saturated fats and cholesterol, regular physical activity, and quitting smoking are primary recommendations to improve cardiovascular health and prevent further arterial damage.
Medications are also used to manage the underlying causes of the disease. Antiplatelet drugs like aspirin reduce the likelihood of blood clot formation on existing plaques. Statins are used to lower LDL cholesterol levels and help stabilize plaques, making them less prone to rupture, while other medications control high blood pressure and diabetes.
For patients with severe arterial blockages unresponsive to other treatments, invasive procedures may be considered. Angioplasty uses a small balloon to widen the artery, often followed by placing a stent to prop it open. However, these interventions for intracranial arteries are complex and carry their own risks, making them less common than for arteries in the heart.