Generally, strokes are categorized into two major types, ischemic or hemorrhagic. Ischemic strokes occur when a blood vessel in the brain becomes blocked due to a blood clot or excessive plaque buildup among the artery walls. Plaque buildups are usually consequences of other arterial and blood-related conditions, such as atherosclerosis or high cholesterol.
About 85 percent of strokes are ischemic, and they are more common in older adults. There are two types of ischemic stroke: thrombotic and embolic.
Thrombotic strokes are consequences of infected or damaged cerebral arteries that are blocked by blood clots or plaque buildup in blood vessels of the brain. It is also known as a cerebral thrombosis or cerebral infraction, as it occurs deep within the brain. Symptoms can occur slowly over time, as the blockage process is usually gradual. Other medical conditions, such as sickle cell anemia or atherosclerosis, often set the stage for thrombotic strokes, since blood vessel and artery blockage is often a symptom of the conditions. When a piece of a clot, also known as a thrombus, breaks off, it can lead to an embolic stroke.
Embolic strokes occur as a result of free-traveling blood clots that are developed far away from the brain. For example, a section of a plaque from the heart can break off and travel through the blood stream until it is lodged in the smaller, narrower vessels in the brain. However, such clots can also be other debris, such as fat, air bubbles, cancer cells or clumps of bacteria. Sometimes, irregular heart beating, such as atrial fibrillation, contributes to free-traveling clot formation due to irregular blood flow. While embolic strokes can be treated by dissolving the blockage, the underlying source of the free-traveling plaque or debris will need to be addressed by a doctor to prevent future recurring cases.
The second type of stroke, hemorrhagic strokes, occurs due to a leakage or a ruptured artery in the brain. Although hemorrhagic strokes are rare in comparison to ischemic strokes, they are often more deadly, because the bleeding in the brain can quickly turn fatal. Hemorrhaging in the brain can be caused by many conditions, including uncontrolled high blood pressure, weak spots in blood vessels and head trauma. Hemorrhagic stroke patients will experience extreme pressure in the head. The two types of hemorrhagic stroke are intracerebral and subarachnoid.
In an intracerebral hemorrhage, an inflamed blood vessel deep inside the brain becomes weak and ruptures, spilling blood into the surrounding brain tissue and causing severe pressure and damage to the area. Brain cells beyond the rupture are also injured due to blood deprivation at the hemorrhage site. Hypertension, or high blood pressure, is the main culprit in intracerebral hemorrhages, as it makes small vessels inside the brain more susceptible to cracking and leaking. This condition is also known as a cerebral aneurysm, and can often become fatal, as an affected individual can collapse, become unconscious and die within minutes and without warning.
In a subarachnoid hemorrhage, an artery on or near the surface of the brain ruptures, and blood is spilled into the space between the brain and the skull. The hemorrhage is often signaled as a sudden, severe headache, usually described as a "thunderclap" effect, accompanied by a sudden urge to vomit. This type of bleeding is commonly caused by the bursting at a weak spot in a vessel. Affected individuals may quickly become unconscious and possibly die due to the sudden drastic increase of pressure in the brain. Subarachnoid aneurisms can affect people of any age.
Transient Ischemic Attack (TIA)
A transient ischemic attack (TIA), also known as a "mini stroke," is a brief episode where symptoms similar to those of a stroke are present. The cause of a TIA is a temporary decrease in blood supply to a part of the brain. Similar to an ischemic stroke, an attack occurs when a clot or plaque buildup decreases blood flow to a part of the brain. But unlike a stroke, a TIA does not have a lasting effect, as it only decreases the blood flow, and does not usually cause permanent tissue damage. Many TIAs last less than 5 minutes, and symptoms can include sudden weakness in one side of the body, blurred vision, vertigo or sudden, severe headache with no known cause. Sometimes, the clots that caused the transient ischemic attack may spontaneously dissolve.
While TIAs are temporary and symptoms are brief, it is still crucial to immediately seek emergency care. Transient ischemic attacks are usually indicators of partially blocked or narrowed arteries, and are often precursors to full-blown strokes that can cause permanent damage, or even death. If you experience any symptoms that are similar to a stroke, then you may have a transient ischemic attack. See your doctor as soon as possible for a checkup.