Approximately 75-80% of strokes are of the clotting (ischemic) variety, while the remainder (hemorrhagic strokes) are due to bleeding from broken blood vessels. Sometimes platelets (cells in the blood stream responsible for clotting) become 'sticky' and promote clotting. If the blood clots too easily it can result in blood flow blockage and subsequent tissue death in that part of the brain normally nourished by the affected blood vessel. You can reduce the risk of the blockage type strokes by keeping your blood platelets from becoming sticky. A completed stroke is caused by irreversible brain injury due to the interruption of blood flow. In contrast, a transient ischemic attack (TIA) is a temporary focal neurologic deficit caused by the brief interruption of local cerebral blood flow. Strokes occur in one third of patients who have a TIA.

The duration of a focal neurologic deficit that leads to cerebral infarction has arbitrarily been determined to be 24 hours or greater. Any focal neurologic deficit that resolves completely within 24 hours is considered a TIA. The diagnosis of a TIA indicates that no irreversible neurologic injury has occurred and provides an excellent opportunity to prevent permanent damage.

The first step in the evaluation of a patient with possible TIA is to determine if the event in question actually represents a TIA. Certain conditions should be ruled out before the diagnosis of TIA is made. Excluding other diagnoses reduces the possibility of inappropriately labeling a patient with the diagnosis of cerebrovascular disease and launching into a course of costly and potentially dangerous diagnostic testing.

The symptoms of a TIA depend on the region of the brain that is supplied by the transiently occluded cerebral artery.
If a TIA is recognized, steps can be taken to prevent future ischemic stroke. All TIAs should be promptly investigated because the risk of ischemic stroke is highest soon after a TIA.

Elevated blood pressure increases the risk of stroke substantially. Discontinuing hypertensive medication with a return of high blood pressure significantly increases the risk of stroke, especially for someone under the age of 55. Hypertensives are strongly advised not to discontinue medication permanently unless their blood pressure stays close to the normal range.

One study found that while patients on pressure-lowering medications still faced double the stroke risk of healthy controls, patients who abandoned these medications had nearly five times the risk. They authors speculate that the thinning of the arterial wall that occurs with the use of many antihypertensive drugs (due to lowered pressure) might render the wall more subject to injury from high pressure that may occur when medications are ceased. The stroke risk associated with stopping hypertension medication appears to be even higher - almost eight times higher in patients under the age of 55 years than in older patients. This phenomenon might be explained by the vascular thickening that accompanies aging.

Sometimes symptoms of a stroke are difficult to identify. Unfortunately, the lack of awareness spells disaster. The stroke victim may suffer brain damage when people nearby fail to recognize the symptoms of a stroke. Now doctors say a bystander can recognize a stroke by asking three simple questions:

Ask the individual to SMILE.
Ask him or her to RAISE BOTH ARMS.
Ask the person to SPEAK A SIMPLE SENTENCE (Coherently) (ie. It is sunny out today)

If he or she has trouble with any of these tasks, call 911 immediately and describe the symptoms to the dispatcher.