Transient ischemic attack

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Aysha Anwar, M.B.B.S[2]

A transient ischemic attack is caused by the temporary disturbance of blood supply to a restricted area of the brain, resulting in brief neurologic dysfunction that usually persists for less than 24 hours.

Discontinuation of the use of the term transient ischemic attack has been proposed^[1].

The most common cause of a TIA is an embolus (a small blood clot) that occludes an artery in the brain. This most frequently arises from an atherosclerotic plaque in one of the carotid arteries (i.e. a number of major arteries in the head and neck) or from a thrombus (i.e. a blood clot) in the heart due to atrial fibrillation. Other reasons include excessive narrowing of large vessels due to an atherosclerotic plaque and increased blood viscosity due to some blood diseases. TIA is related with other medical conditions like hypertension, heart disease (especially atrial fibrillation), migraine, cigarette smoking, hypercholesterolemia, and diabetes mellitus.

Symptoms vary widely from person to person depending on the area of the brain involved. The most frequent symptoms include temporary loss of vision (typically amaurosis fugax), difficulty speaking (dysarthria), weakness on one side of the body (hemiparesis), numbness usually on one side of the body, and loss of consciousness. If there are neurological symptoms persisting for more than 24 hours, it is classified as a cerebrovascular accident (stroke).

An electrocardiogram (ECG) may show atrial fibrillation, a common cause of TIAs, or other arrhythmias that may cause embolisation to the brain.

TIAs do not show brain changes on CT scans. (Most strokes do show changes on such tests).

TIAs do not show brain changes on MRI scans. (Most strokes do show changes on such tests).

An echocardiogram is useful in detecting thrombus within the heart chambers. Such patients benefit from anticoagulation.

If the TIA affects an area supplied by the carotid artery, an ultrasound (TCD) scan may demonstrate carotid stenosis.

For people with a greater than 70% stenosis within the carotid artery, removal of atherosclerotic plaque by surgery, specifically a carotid endarterectomy, may be recommended.

Prevention of TIAs includes controlling risk factors, such as high blood pressure, diabetes, heart disease, and other associated disorders. Smoking should be stopped.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Aysha Anwar, M.B.B.S[2]

The concept of TIA was first discussed in 1950 by Charles Miller Fischer based on the observation that transient ischemic stroke in patients may lead to stroke in the same arterial territory in the future. He also proposed that treatment and prevention of transient ishemic attack may help prevent the patient from full blown stroke in the future. ^[1]

The concept of TIA was first discussed in 1950 by Charles Miller Fischer based on the observation that transient ischemic stroke in patients may lead to stroke in the same arterial territory in the future. He also proposed that treatment and prevention of transient ishemic attack may help prevent the patient from full blown stroke in the future. ^[1][2]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Aysha Anwar, M.B.B.S[2]

The pathophysiologic mechanism of transient ischemic stroke may include temporary blockage of cerebral large or small blood vessel due to atherothrombotic or embolic cause followed by complete resolution of symptoms within few hours of onset. There may be mild tissue ischemia and hypoxia responsible for transitory symptomatology of patient. The specific clinical presentation of the patient correlates with the area of brain affected due to ischemia^[1][2]

According to American stroke association, transient ischemic stroke is defined as a transient episode of neurological dysfunction caused by a focal brain, spinal cord, or retinal ischaemia, without acute infarction.^[1]

The pathophysiologic mechanism of transient ischemic stroke may include temporary blockage of large or small cerebral blood vessel due to atherothrombotic or embolic cause followed by complete resolution of symptoms within few hours of onset. There may be mild tissue ischemia and hypoxia responsible for transitory symptomatology of patient. The specific clinical presentation of the patient correlates with the area of brain affected due to ischemia^[1][2]

There may be genetic predisposition in patients suffering from transient ischemic stroke.^[3][4][5]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

The most common cause of a TIA is an embolus (a small blood clot) that occludes an artery in the brain. This most frequently arises from an atherosclerotic plaque in one of the carotid arteries (i.e. a number of major arteries in the head and neck) or from a thrombus (i.e. a blood clot) in the heart due to atrial fibrillation. Other reasons include excessive narrowing of large vessels due to an atherosclerotic plaque and increased blood viscosity due to some blood diseases. TIA is related with other medical conditions like hypertension, heart disease (especially atrial fibrillation), migraine, cigarette smoking, hypercholesterolemia, and diabetes mellitus.

The etiology of TIA may be divided in to following based on the pathophysiology involved:

• Caused by atherosclerosis of internal carotid artery at origin or intracranially
• Also called low flow TIA
• Lasts few minutes to hours
• May cause recurrent TIAs producing stereotyped symptoms based on the branches of vessel involved

• Caused by an embolic source from artery or heart
• Common causes of embolism include atrial fibrillation and ventricular thrombus
• Usually lasts hours

• Involves small penetrating intracerebral vessels
• Usually caused by atheroscerotic narrowing of small blood vessels or lipohyalanosis
• May invlove internal capsule, basal ganglia or thalamus

• Commonly cause symptoms due to cerebral ischemia or embolism
• Interruption of blood flow at the petrous portion of internal carotid artery or at the level of C1-C2 of vertebral artery as it enters foramen transversarium
• Symptoms may last from minutes to hours to days.
• May be detected by neurovascular imaging

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1], Associate Editor(s)-in-Chief: , Aysha Anwar, M.B.B.S[2]

The differential diagnosis of TIA may include seizures, hypoglycemia, electrolyte disturbances, migraine, renal, hepatic or pulmonary encephalopathy, syncope , subdural hematoma, ischemic stroke, brain tumour, conversion disorder, multiple sclerosis, compressive myelopathy of spinal cord, vestibular disorders, cerebral amyloid angiopathy, nerve root compression, orthostatic hypertension, hypertensive encephalopathy ^[1][2][3]

The differential diagnosis of TIA may include:^[1][2][3]

• Hypoglycemia
• Electrolyte disturbances
• Migraine
• Renal, hepatic or pulmonary encephalopathy
• Syncope
• Subdural hematoma
• Ischemic stroke
• Brain tumour
• conversion disorder
• Multiple sclerosis
• Compressive myelopathy of spinal cord
• Vestibular disorders
• Cerebral amyloid angiopathy
• Nerve root compression
• Orthostatic hypertension
• Hypertensive encephalopathy
• Seizures
• Transient neurological attack

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Aysha Anwar, M.B.B.S[2]

The estimated incidence of TIA may range from 200,000 to 500,000 per year. The estimated prevalence of TIA approximates to about 5 million people which correlates to population prevalence of 2.3%. ^[1][2][3]

There may be certain limitations to assess the accurate incidence and prevalence data on transient ischemic stroke due to different criterias used for TIA in different epidemiological studies. Also, there may be underestimation of transient focal neurological symptoms by public and health care system. However, the estimated incidence and the prevalence of TIA in USA in year the 1999 is as follows:^[1][2][3]

• The estimated incidence of TIA may range from 200,000 to 500,000 per year.^[1][2][3]
• The estimated prevalence of TIA approximates to about 5 million people which correlates to population prevalence of 2.3%.^[1][2][3]

The incidence of TIA increases remarkably with age irrespective of gender and race.^[1]

The incidence of TIA is more common in males.^[1]

The incidence of TIA is high among African American race in older age group. However, the incidence of TIA is reported to be high in Mexican Americans compared with non-Hispanic whites at younger ages.^[1]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Aysha Anwar, M.B.B.S[2]

The risk factors of transient ischemic attack may include modifiable and non modifiable risk factors such as age, sex, race, coronary artery disease, atrial fibrillation, hypercoaguable state, hypertension, diabetes mellitus, cigarette smoking and alcohal consumption.^[1][2][3]

The risk factors of transient ischemic attack may include modifiable and non modifiable risk factors:^{[1][2][3][4][5][6][7]}

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Aysha Anwar, M.B.B.S[2]

If left untreated, the symptoms of transient ischemic attack may subside with in few hours. However, there is increased risk of stroke in these patients in future. The risk is highest in the next within hours and subsequently decreases after days, weeks to months.^[1]The prognosis of TIA depends on the possibilty of developing ischemic stroke in the future. There is 11 percent increased risk of ischemic stroke in patients having TIA for next seven days and 25-29% in next five years.^[2] This is especially true in patients with TIA due to small-vessel disease (SVD) etiology with motor weakness (capsular warning syndrome).^[2]

If left untreated, the symptoms of transient ischemic attack may subside with in few hours. However, there is increased risk of stroke in these patients in future. The risk is highest in the next within hours and subsequently decreases after days, weeks to months.^[1]

Complications of TIA include:^{[3][4][5][6][7]}

• Ischemic stroke
• Hemorrhagic stroke
• Dementia
• Recurrent TIA
• Anxiety

The prognosis of TIA depends on the possibilty of developing ischemic stroke in the future. There is 11 percent increased risk of ischemic stroke in patients having TIA for next seven days and 25-29% in next five years.^[2] This is especially true in patients with TIA due to small-vessel disease (SVD) etiology with motor weakness (capsular warning syndrome).^[2]

The ABCD² score can predict likelihood of subsequent stroke.^[8][9][10]

The score is calculated as:
Age

• ≥ 60 years = 1 point
• Blood pressure at presentation ≥ 140/90 mm Hg = 1 point

Clinical features

• Unilateral weakness = 2 points
• Speech disturbance without weakness = 1 point

Duration of attack

• ≥ 60 minutes = 2 points
• 10–59 minutes = 1 point
• Diabetes = 1 point

Interpretation of score, the risk for stroke:
Score 0-3 (low)

• 2 day risk = 1.0%
• 7 day risk = 1.2%

Score 4-5 (moderate)

• 2 day risk = 4.1%
• 7 day risk = 5.9%

Score 6–7 (high)

• 2 day risk = 8.1%
• 7 day risk = 11.7%

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