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Stroke and TIA

Stroke and TIAA cerebrovascular accident (CVA), more commonly known as stroke, is a sudden impairment of cerebral circulation in one or more of the blood vessels supplying the brain. Stroke interrupts or diminishes oxygen supply and frequently causes serious damage or necrosis in brain tissues. The sooner the circulation returns to normal after a stroke, the better chances are for complete recovery.

Strokes are classified according to their course of progression. The least severe is the transient ischemic attack (TIA), or “little stroke,” which results from a temporary interruption of blood flow. A progressive stroke, or stroke-in-evolution (thrombus-in- evolution), begins with slight neurologic deficit and worsens in a day or two. In a complete stroke, neurologic deficits are maximal at onset.

Stroke is the third most common cause of death in the United Stated today and the most common cause of neurologic disability. It strikes 500,000 people each year; half of them die as a result. About half of those who survive stroke remain permanently disabled and experience a recurrence within weeks, months, or years.

Clinical features of stroke vary with the artery affected (and, consequently, the portion of the brain it supplies), the severity of damage, and the extent of collateral circulation that develops to help the brain compensate for decreased blood supply. If stroke occurs in the left hemisphere, it produces symptoms on the right side. If in the right hemisphere, symptoms are on the left side. However, a stroke that causes cranial nerve damage produces signs of cranial nerve dysfunction on the same side as the hemorrhage. Symptoms are usually classified according to the artery affected. Symptoms can also be classified as premonitory, generalized, and focal.

TIA, or transient ischemic attack, is a recurrent episode of neurologic activity. It lasts from seconds to hours and clears within 12 to 24 hours. It is usually considered as a warning sign of an impending thrombotic CVA. In fact, TIAs have been reported in 50% to 80% of patients who have had a cerebral infarction from such thrombosis. The age of onset varies. Incidence rises dramatically after age 50 and is highest among blacks and men.

In TIA, microemboli released from a thrombus probably temporarily interrupt blood flow, especially in the small distal branches of the arterial tree in the brain. Small spasms in those arterioles may impair blood flow and also precede TIA. Predisposing factors are the same as for thrombotic CVAs. The most distinctive characteristics of TIAs are the transient duration of neurologic deficits and complete return of normal function.

The symptoms of TIA easily correlate with the location of the affected artery. These symptoms include double vision, speech deficits (slurring or thickness), unilateral blindness, staggering or uncoordinated gait, unilateral weakness or numbness, falling because of weakness in the legs, and dizziness.

During an active TIA, the aim of treatment is to prevent a completed stroke and consists of aspirin or anticoagulants to minimize the risk of thrombosis. After or between attacks, preventive treatment includes carotid endarterectomy or cerebral microvascular bypass.

December 23, 2009  Tags: , , , ,   Posted in: earlysymptoms