Stenosis is the abnormal narrowing of a passage or vessel within the body. When this narrowing affects the arteries supplying blood to the brain, it is called cerebral stenosis (intracranial or extracranial stenosis). This serious vascular disorder impedes the brain’s supply of oxygen and nutrients. Even a temporary reduction in blood flow can have devastating consequences for neurological function.
Defining Cerebral Stenosis and Its Impact
Cerebral stenosis involves the constriction of arteries both outside the skull (extracranial, like the carotid arteries) and inside the skull (intracranial). Common sites for this narrowing include the internal carotid arteries, middle cerebral artery, and basilar artery. When the arterial lumen diameter is reduced, the volume of blood that can pass through is lowered.
This decrease in blood flow creates ischemia, depriving brain tissue of adequate oxygen and glucose. Ischemia is the mechanism leading to the most serious complications: Transient Ischemic Attack (TIA) and ischemic stroke. A TIA is a temporary event where the blockage resolves before permanent damage occurs, often serving as a strong warning sign. The ultimate risk is that diminished flow or a complete blockage caused by a traveling clot will result in the death of brain cells, causing a permanent stroke.
Recognizing the Warning Signs
The signs of cerebral stenosis relate to the area of the brain experiencing oxygen deprivation. Many people remain asymptomatic until the narrowing becomes severe or a stroke-like event occurs. Persistent symptoms might include chronic headaches, dizziness, or lightheadedness resulting from chronically poor blood flow.
Acute symptoms, signaling a TIA or stroke, require immediate medical attention. These sudden changes include weakness, numbness, or paralysis affecting one side of the face, arm, or leg. Vision changes, such as sudden blurring or loss of sight in one eye, are common warning signs. Difficulty with speech, characterized by slurred words or an inability to understand language, indicates a neurological event caused by interrupted blood supply.
Identifying the Underlying Causes
The most frequent cause of cerebral stenosis is atherosclerosis, the progressive hardening and narrowing of arteries due to plaque buildup. Plaque is composed of cholesterol, cellular waste products, and calcium, accumulating on the inner walls of blood vessels over time. The presence of plaque narrows the artery and makes the surface rough, increasing the likelihood of a blood clot forming and causing a sudden blockage.
Other, less common conditions can also lead to the narrowing of brain arteries. Fibromuscular dysplasia (FMD) is a non-atherosclerotic condition where abnormal cell growth causes artery walls to narrow, bulge, or appear beaded. Vasculitis, the inflammation of blood vessel walls, can also result in stenosis. Additionally, a history of radiation therapy to the head or neck may contribute to arterial wall damage and subsequent narrowing.
Medical Confirmation and Assessment
Diagnosis begins with a physical examination and a review of the patient’s medical history, focusing on any sudden neurological symptoms. Doctors rely on specialized imaging tests to visualize blood vessels and measure the degree of narrowing. The initial non-invasive screening tool is the Doppler ultrasound, which uses sound waves to assess blood flow velocity and identify blockages, particularly in the carotid arteries.
More detailed non-invasive imaging involves Magnetic Resonance Angiography (MRA) or Computed Tomography Angiography (CTA). MRA uses magnetic fields to create detailed images of the blood vessels. CTA uses X-rays and an injected contrast dye to highlight the arteries, demonstrating high sensitivity for detecting and quantifying intracranial stenosis.
The most definitive, though invasive, method is conventional angiography, also known as Digital Subtraction Angiography (DSA). This procedure involves inserting a catheter into an artery, guiding it to the brain’s vessels, and injecting contrast dye while taking X-ray images. DSA remains the reference standard for precise stenosis measurements but is often reserved for cases where non-invasive tests are inconclusive or when an interventional procedure is planned.
Managing and Treating the Condition
The primary goal of treating cerebral stenosis is preventing stroke by restoring adequate blood flow and minimizing clot formation risk. Treatment is tailored to the stenosis severity and whether the patient has experienced symptoms like TIA or stroke. Aggressive medical management is the first line of defense for many patients.
Medical therapy involves controlling risk factors and preventing clots using medication. Antiplatelet drugs, such as aspirin and clopidogrel, are commonly prescribed to reduce platelet stickiness and inhibit clot formation within the narrowed artery. High-intensity statin therapy manages high cholesterol, stabilizing existing plaque and reducing further buildup. Strict control of high blood pressure and diabetes is also incorporated into the comprehensive medical plan.
When stenosis is severe or symptoms persist despite aggressive medication, interventional procedures may be necessary. Carotid endarterectomy is a surgical option for significant extracranial carotid blockages, involving a neck incision to surgically remove the plaque. For intracranial stenosis, or as an alternative for carotid disease, an endovascular approach is often used.
This procedure involves angioplasty and stenting. A catheter is threaded through the arteries to the narrowing site, where a small balloon is inflated to compress the plaque against the artery wall. This is followed by the placement of a mesh tube, or stent, to keep the vessel permanently open. The decision to proceed with a surgical or endovascular intervention is made when the risk of stroke from the stenosis outweighs the risks associated with the procedure itself.