A stroke occurs when blood flow to a part of the brain is interrupted, depriving brain cells of oxygen and nutrients. The majority of strokes (about 87%) are ischemic strokes, caused by a blockage in a blood vessel. A thrombotic stroke is a specific type of ischemic stroke where a blood clot, known as a thrombus, forms directly within a brain artery, completely obstructing blood flow.
Understanding the Thrombotic Process
The formation of a thrombus is rooted in atherosclerosis, the hardening and narrowing of arteries due to plaque buildup. Plaque, composed of fatty substances, cholesterol, and calcium, accumulates beneath the inner lining of the artery wall, making the vessel stiff and uneven. This buildup gradually reduces the blood vessel’s diameter, a condition known as stenosis. The rough, damaged surface of the plaque triggers the body’s clotting mechanism. Platelets and clotting proteins adhere to the exposed plaque, initiating the formation of a thrombus right at the site of damage. As the thrombus grows, it eventually blocks the artery completely, cutting off blood supply to the brain.
This mechanism distinguishes a thrombotic stroke from an embolic stroke, where the blockage (embolus) forms elsewhere, often the heart, and travels to lodge in a smaller brain artery. Because a thrombus develops directly in the affected artery, the onset of a thrombotic stroke is often slower and may happen during periods of rest or sleep. The resulting lack of oxygen rapidly causes brain cell death, leading to neurological deficits.
Key Conditions That Lead to Thrombotic Stroke
Several chronic health problems create the environment for atherosclerosis and subsequent thrombus formation. Uncontrolled hypertension significantly damages the delicate inner lining of the blood vessels, making them more susceptible to plaque buildup. High cholesterol levels contribute directly to the atherosclerotic plaque content, speeding up arterial narrowing.
Diabetes is another major contributor, as high blood sugar levels damage blood vessels throughout the body, increasing the risk of clotting. Lifestyle factors also play a large role, particularly smoking, which causes injury to the arterial walls and promotes blood thickening. Managing these conditions is the primary way to prevent the chronic vessel damage that precedes a thrombotic stroke.
Recognizing the Signs of a Stroke
Recognizing the sudden onset of stroke symptoms requires immediate action. Healthcare providers use the acronym F.A.S.T. to identify the most common signs: Face drooping, Arm weakness, Speech difficulty, and Time to call emergency services. A person may have one side of their face droop when smiling, or one arm may drift downward when trying to raise both arms.
Speech may be slurred, or the person may have trouble understanding simple commands. Other symptoms include sudden confusion, severe headache with no known cause, or trouble walking and loss of balance. Even if symptoms are temporary, indicating a Transient Ischemic Attack (TIA), it must be treated as a medical emergency because a TIA is a powerful warning sign that a full stroke may follow.
Acute Care and Emergency Treatment
Upon arrival at the hospital, the priority is to determine the type of stroke and the location of the blockage to facilitate rapid treatment. Diagnostic imaging, typically a non-contrast CT scan or an MRI, is performed immediately to confirm an ischemic stroke and rule out a hemorrhagic stroke. The guiding principle for care is “time is brain,” as treatment must be delivered within a narrow window to minimize permanent damage. The primary treatment for an ischemic stroke is intravenous thrombolysis, administering a medication like tissue plasminogen activator (TPA) that dissolves the blood clot. This “clot-busting” drug is only effective if given within 4.5 hours of symptom onset.
For patients with a blockage in a large brain artery, detected by a CT angiogram, mechanical thrombectomy may be performed. During this procedure, a specialist threads a catheter through an artery, usually in the groin, up to the blocked vessel in the brain. A device is then used to physically remove the thrombus, restoring blood flow. This procedure can be performed for up to 24 hours after symptom onset in select patients, though earlier treatment yields better outcomes. Once blood flow is restored, blood pressure and blood sugar are closely monitored to support the brain’s recovery.