Two kinds of Strokes
Strokes, defined as a loss of brain function after an interruption of blood supply to the brain, come from two causes: clots and bleeds.
The most common, occurring in over 80 percent of cases, is an Ischemic stroke. In this case a blood vessel is blocked with a clot of plaque, restricting blood flow into the brain.
A hemorrhagic stroke makes up the remaining cases. It happens when a weakened blood vessel ruptures, spilling blood into the brain tissues. All strokes are dangerous but this variety tends to cause the most damage and have the poorest prognosis for survival and recovery.
Strokes vary in severity, from temporary paralysis, disorientation, and slurred speech to permanent brain damange, manifesting in different ways depending on which area of the brain was destroyed, and even death.
The human body is usually quite adept and efficiently transporting blood to the organs that need them, and the brain is one of the most important.
This system breaks down, in the case of ischemic strokes, when cholesterol in the blood deposits in areas, creating plaque that narrows a blood vessel and slows blood flow to a crawl.
There are two main sources of blood vessel blockage:
In cerebral thrombosis, a clot develops behind the plaque-clogged part of the vessel, and can further narrow or block blood flow entirely.
In cerebral embolism, a blood clot forms elsewhere (for example in the heart in the case of atrial fibrillation, or within a large artery), then breaks loose and drifts along blood vessels until it get to the increasingly small branches of blood vessels in the brain. At some point, the clot comes to a stop and blocks blood flow to that vital area.
Hemorrhagic strokes happen when a blood vessel tears open under the pressure of the fluid it carries. The blood spills into the surrounding brain, compressing and damaging the delicate neural tissue.
There are two kinds of hemorrhagic stroke, named for where the disruption occurs: intracerebral hemorrhage and subarachnoid hemorrhage.
An intracerebral hemorrhage is when a blood vessel directly within the brain gives way and blood pools within the tissues themselves. It is more likely to occur within certain areas of the brain, such as the cerebellum, brain stem, and cortex.
When a blood vessel breaks just outside the brain, a subarachnoid hemorrhage occurs. The area between the brain and the skull fills with blood, causing intense pressure on the neural tissues.
Both kinds of hemorrhage are serious and both come from the same root causes:
The blood vessels have been weakened prior to the stroke, usually by an aneurysm or by arteriovenous malformation. An aneurysm is a bulge in the wall of a blood vessel caused by it thinning and weakening; it is vulnerable to tear under pressure. Arteriovenous malformation, or AVM, is an abnormal connection formed between clusters of blood vessels while the person is in utero. It is also vulnerable to fail under pressure.
As you can tell, both of these conditions are aggravated by high blood pressure. Hypertension, if left uncontrolled by diet and medication, strains all of the body’s systems and these already vulnerable areas of the blood vessels are likely to give way at some point.