Transient Ischemic Attack
What Is It?
A transient ischemic attack (TIA) is characterized by transient neurological symptoms that are brought on my ischemia to the brain (decrease in blood flow). By definition, a TIA is transient, meaning that the symptoms spontaneously resolve completely within 24 hours of their onset. In a sense, a TIA is fundamentally similar to a stroke (cerebral infarction) except that the neurological symptoms do not persist beyond 24 hours and the patient is left with no long term disability.
Transient ischemic attacks generally occur due to a blockage of one of the blood vessels supplying the brain, similar to an ischemic stroke. However, either by spontaneous dissolution of the causative blood clot or by recruitment of collateral blood circulation to the brain, the affected brain does not die, as in an ischemic stroke or infarction, but rather recovers and regains function.
Transient ischemic attacks are generally caused by small blood clots, usually traveling in the blood from an area of atherosclerosis in a larger blood vessel (the carotid artery in the neck for example), which lodge in a small blood vessel that supplies the brain. If the clot does not dissolve and there is not adequate collateral blood flow to that part of brain the brain will die (a cerebral infarction) and the patient may have permanent symptoms.
The risk factors for TIAs are the same as ischemic stroke and infarction. Therefore, TIAs are often considered warning signs that a patient is prone to clot formation and that they may be at risk for stroke in the future if they are not treated appropriately. TIAs can occur in patients who have never had a stroke or in patients who have already had strokes in the past.
Common risk factors for cerebrovascular disease which leads to TIAs and stroke include high blood pressure, diabetes mellitus, smoking, high cholesterol, obesity and sedentary lifestyle.
What Types of Symptoms Are Typical?
The neurological symptoms that occur with a transient ischemic attack depend entirely on the area of the brain which is affected. This can include just about any neurological symptom such as sensory changes, weakness, blindness, speech difficulties, etc.
One of the most common locations for blood clots to lodge and cause TIAs or strokes are in the distribution of the middle cerebral artery (MCA). Because this artery supplies blood to much of the area of the brain which controls movement, a common symptom of TIAs is weakness of the opposite side of the body. Language function is also often in the MCA territory. Language is generally localized to only one side of the brain, called the dominant hemisphere. In most people, particularly right-handed people, this is on the left side of the brain. In a small set of people, more common in left-handed people, the left hemisphere can be dominant. If the dominant hemisphere is affected by a transient ischemic attack or stroke, language dysfunction, called aphasia, can occur as well.
The symptoms of a transient ischemic attack, like a stroke, generally come on suddenly and without warning. They may last only minutes to hours. The symptoms must completely resolve by 24 hours from their onset to be considered a TIA.
How Is The Diagnosis Typically Made?
If a patient presents with new neurological symptoms of sudden onset, they are generally worked up for various forms of stroke. This generally includes a CT scan
to rule out hemorrhagic stroke as well as an MRI scan
of the brain to evaluate for evidence of ischemia and infarction in the brain. The diagnosis of TIA is made if these ischemic symptoms spontaneously resolve within 24 hours of onset.
If a patient has a TIA or stroke, they are generally worked up for an underlying cause. For example, their carotid arteries in their neck are evaluated (usually by duplex ultrasound) for atherosclerosis and any blockage which could have been the source of the clot. If this is not found, other sources are often investigated. For example, the heart may be studied to determine if the patient has clot inside the heart that could be the source, as can occur with an arrhythmia of the heart called atrial fibrillation.
What Are Some Common Treatments?
Because a transient ischemic attack is by definition transient, no treatment for the brain itself is generally necessary. However, TIAs are considered a warning sign that a patient is forming clots and is therefore at risk for further ischemic events, including further TIAs or strokes. Therefore, patients who present with a TIA are generally worked up for risk factors and causative factors including high blood pressure, high cholesterol, diabetes mellitus, carotid stenosis (blockage of the carotid artery in the neck) and atrial fibrillation, etc.
If any of these risk factors are found, an attempt is made to reverse them where possible. This includes treating high blood pressure and cholesterol, controlling diabetes, treating atrial fibrillation if present, smoking cessation, weight loss, and exercise. Additionally, if the patient has evidence of significant carotid stenosis, a procedure is often considered to treat this. This can involve either endovascular angioplasty and stenting of the area of atherosclerosis or surgery, called a carotid endarterectomy, to remove the plaque causing the blockage.
Furthermore, some patients will be prescribed blood thinning medications to reduce the risk of clotting. The most common of these is simple aspirin which inhibits platelet clotting. In some cases, particularly if the patient has atrial fibrillation, has had angioplasty and stenting, or has a history of a heart valve replacement, stronger blood thinning medications will be added. These can include various drugs such as plavix, coumadin (warfarin), and heparin.
If a patient's symptoms are not transient and have not reversed completely, they are treated for an ischemic stroke which can include several other treatments depending on how early they come to medical attention after the onset of symptoms. You can read more about the treatments for ischemic stroke on our Ischemic Stroke page.
The individual treatment of a given patient with a transient ischemic attack or stroke can be very different depending on the specifics of each case. Each patient should discuss the appropriate treatment options with their own treating physicians.
Return to the Stroke page from the Transient Ischemic Attack page.
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This site is not intended to offer medical advice. Every patient is different, and only your personal physician can help to counsel you about what is best for your situation. What we offer is general reference information about various disorders and treatments for your education.