TIAs Often First Signs of Imminent Stroke

Stroke
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Strokes are the leading cause of disability and the third leading cause of death in the United States. Transient ischemic attacks (TIAs) are often the first signs of an imminent stroke.

An estimated 795,000 Americans experience a new or recurrent stroke each year. It is important to recognize the early signs of stroke so that treatment can be gotten early and damage minimized.

The original 1975 definition of TIA states it is a focal neurologic deficit caused by focal brain ischemia that completely resolves in less than 24 hours. It was thought that symptoms lasting less than 24 hours were unlikely to cause infarction and permanent impairment. In fact, most TIAs resolve within one hour and if they do not, there is less than a 15% chance that they will resolve within 24 hours.

A newer definition proposed in the New England Journal of Medicine in 2002 emphasizes the distinction between ischemia (TIA) and infarction (stroke). This definition states that “a TIA is a brief episode of neurologic dysfunction caused by focal brain or retinal ischemia, with clinical symptoms typically lasting less than one hour, and without evidence of acute infarction.”

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TIA and ischemic stroke share the same pathophysiology. Risk factors for both include hypertension, smoking, obesity, and diabetes. Both may be due to areas of stenosis in major vessels such as the internal carotid artery or the anterior, middle, or posterior cerebral artery, or in the vertebral or basilar artery. Stenosis may also occur in the smaller penetrating arteries, usually from longstanding hypertension or diabetes. Embolic TIAs and strokes generally arise from cardiac pathology but may also result from primary vascular disease such as atherosclerosis.

Clinical symptoms of TIA may vary widely depending on which part of the brain circulation is involved. Symptoms may include temporary blindness in one eye which is often simply a visual field defect rather than complete blindness. There may be unilateral weakness, paralysis, or numbness in the lower extremities. There may be weakness, paralysis, or numbness on one side of the face and in the opposite arm. There may be aphasia or difficulty with speech, ataxia (difficulty with balance), vertigo, nausea, and vomiting.

Since it is estimated that 25% of strokes are preceded by TIA, if you have any of the above symptoms you should be seen in the emergency department. Don’t wait to see if the symptoms go away. If you are having a stroke rather than a TIA, being seen early can allow treatment which can minimize the damage done by the stroke.

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Sources
Albers GW, Caplan LR, Easton JD, et al. Transient ischemic attack—proposal for a new definition. N Engl J Med. 2002;347(21):1713-1716.
Shah KH, Edlow JA. Transient ischemic attack: review for the emergency physician. Ann Emerg Med. 2004;43(5):592-604.
National Stroke Association

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