What is Stroke?
Stroke can be caused by either a clot obstructing the flow of blood to the brain (ischemic) or by a blood vessel rupturing and preventing blood flow to the brain (hemorrhagic). It can also be transient, due to a temporary blockage in blood flow that resolves itself in a short period of time.
Ischemic strokes make up the majority (87%) of all strokes. An ischemic stroke occurs when a blood vessel supplying blood to the brain is obstructed, thereby cutting off the supply of oxygen and nutrients. Ischemic strokes can either be embolic (due to a clot that migrated from another part of the body) or thrombotic (due to a clot that forms at the obstructed site). The underlying cause of this obstruction is the development of fatty deposits lining the vessel wall called atherosclerosis. Both types result in decreased blood flow to vital brain cells, which can lead to irreversible cell death and long-term disability.
Hemorrhagic stroke accounts for about 13% of stroke cases. It results from a weakened vessel that ruptures and bleeds into the surrounding brain. The blood then accumulates and compresses the surrounding brain tissue. This results in a stroke by depriving parts of the brain of blood and oxygen. There are two types of hemorrhagic stroke: intracerebral and subarachnoid.
• Intracerebral hemorrhage is the most common type of hemorrhagic stroke and occurs when a diseased blood vessel within the brain bursts and allows blood to leak within the brain. This causes an increase in pressure within the brain, which causes damage to the brain cells surrounding the blood. Hypertension is the primary cause of this condition. Other risk factors include alcohol and drug abuse, increased age, being male and being African American.
• Subarachnoid hemorrhage occurs when a blood vessel just outside of the brain ruptures, causing the area of the skull surrounding the brain to rapidly fill with blood. It is usually caused when an aneurysm swells, weakens the vessel and ruptures. Risk factors include middle age, family history, smoking, excessive alcohol use, being female and being African American.
Transient Ischemic Stroke
A Transient Ischemic Attack (TIA) is sometimes called a mini or warning stroke, and occurs when blood flow is temporarily blocked. A TIA usually lasts less than five minutes and typically resolves itself fairly rapidly leaving no noticeable symptoms or deficits. TIAs are a warning sign that should be taken very seriously, and can indicate that a person is at risk for a serious, debilitating stroke.
TIAs are important predictors of stroke. Don't ignore these symptoms.
If you are not sure whether you are suffering a TIA or stroke call 9-1-1 immediately. If you are suffering a stroke, prompt action can improve your treatment options. Your doctor will determine whether or not you have suffered a stroke, a TIA, or another medical problem.
Effects of Stroke
The brain controls a multitude of functions that we perform every day and often take for granted. The ability to smoothly lift a coffee mug to take a sip is controlled by the motor areas of the brain. The abilities to swallow, stand, see and speak are controlled by other, specific areas of the brain. If the blood flow to any of these areas is blocked or interrupted suddenly, that particular ability is affected or lost completely. The brain stem is also an important part of the brain. It controls breathing and other vital functions for life. Blockage to this area is more frequently fatal if left untreated.
The effects of stroke are widely varied depending on the type of stroke, the area of the brain affected and the extent of the brain injury. Brain injury from a stroke can cause:
• Decreased motor activity (movement of arms or legs)
• Difficulty with speech or the ability to understand speech
• Changes in sensation (such as vision, touch sensation, awareness of body positioning)
• Changes in behavior and thought patterns
• Changes in memory and emotions
• Persistent vegetative state or death if the brain stem is involved
• Locked-in syndrome - an effect whereby you are aware but unable to move or respond