What Is Transient Ischemic Attack (TIA)?
The control centers of the brain
The brain controls how our body functions, how we think, how we see, how we talk, and how we move. The signals to and from the brain are transmitted through the spinal cord to the rest of the body.
- The right side of the brain controls the left side of the body, and the left side of the brain controls the right side of the body. This includes movement and sensation.
- Speech centers usually are located in the Broca's area on the left side of the brain.
- Vision is controlled by the back of the brain in the occipital lobes.
- The carotid arteries provide the majority of the blood supply to these parts of the brain (known as the anterior circulation).
- Balance and coordination are controlled by the cerebellum, or the base of the brain, and its blood supply comes from the vertebral arteries located in the bony canals in the back of the vertebral column (referred to as the posterior circulation).
When an area of the brain loses its blood supply it stops working and the part of the body it controls also stops working. This is what happens with a stroke or CVA (cerebrovascular accident).
When the brain loses blood supply, it tries to restore blood flow. If blood supply is restored, function may return to the affected brain cells, permitting return of function to the affected body part. This is what happens with a TIA (transient ischemic attack). Some may consider this a mini-stroke, however, in reality, it is a stroke that has resolved or has improved functionality in the affected body part.
By definition, a TIA resolves within 24 hours, but most TIA symptoms resolve within a few minutes.
TIAs are often warning signs of a future stroke. The risk of a stroke increases dramatically in the days after a transient ischemic attack, and the TIA may offer an opportunity to find a cause or minimize the risk to prevent the permanent neurologic damage that results because of a stroke.
What Causes Transient Ischemic Attack (TIA)?
Brain cells require oxygen and glucose to function. If the blood supply is lost, then nutrient supply is lost, and the brain cells stop working. The blood supply to brain cells can be lost in a few different ways.
- Blood clots can form in one of the tiny arteries of the brain (thrombosis). This is usually preceded by gradual narrowing of the blood vessel by fatty build-up called plaque. Atherosclerosis (atheroma=deposits of cholesterol and fatty tissue + sclerosis + narrowing) of the brain arteries is the same as the narrowing that occurs in heart arteries preceding a heart attack. A blood clot can form if the plaque ruptures, leading to further blockage of the artery.
- Blood clots can float downstream from the heart and get caught in a tiny blood vessel (embolus). Atrial fibrillation (A fib) is the most common reason for an embolus. In atrial fibrillation, the upper chambers of the heart jiggle and don't beat in a coordinated fashion. This allows blood to become stagnant and form small clots. These clots can embolize to any organ in the body, but the brain is a common target.
- Debris can occlude the blood vessels and stop blood flow. This debris often breaks off from carotid arteries that are narrowed by the atherosclerotic disease process described above.
- Blood vessels can leak and cause bleeding within the brain tissue. An intracerebral hemorrhage (intra=within + cerebral= of the brain + hemorrhage=bleeding) is often caused by high blood pressure which can cause small blood vessel walls to become thin and weak.
What Are the Symptoms and Signs of Transient Ischemic Attack (TIA)?
The symptoms of stroke and TIA are the same and depend upon the particular region of the brain that is affected. But while a stroke is permanent, a TIA by definition resolves its own.
- Neurologic deficits appear suddenly and can affect the ability to move or feel on one side of the body.
- Speech and vision can be affected.
- The affected person may experience confusion, difficulty saying words, or the inability to follow commands.
Because the brain is a large organ, the whole side of an individual's body doesn't need to be affected. Symptoms may be limited to an arm or leg or part of the face. The deficits are also grouped based on the anatomy of the brain. As an example, loss of speech (aphasia) is associated with weakness or numbness on the right side of the body, since speech is controlled by the left of the brain. These symptoms are associated with problems in the anterior circulation from the carotid arteries.
TIAs, like stroke, may have large, obvious neurologic defects like paralysis. However, the symptoms may also be subtle, such as numbness or burning of a limb, or clumsiness with the use of hand or while walking.
If the cerebellum is affected because of issues with the vertebral arteries, the symptoms are much different. Symptoms of posterior circulation stroke or cerebrovascular accident include:
- loss of balance and coordination, and
- trouble walking.
Drop attacks, in which the patient falls suddenly without warning, with or without losing consciousness, occur as a result of a TIA to the base of the brain.
Amaurosis Fugax is a specific type of TIA where there is sudden loss of vision in one eye that resolves spontaneously. It occurs when debris from the carotid artery on the same side occludes one of the ophthalmic arteries and stops blood supply to the retina (the nerve complex in the back of the eye that interprets light and visual signals).
When Should I Call the Doctor About Transient Ischemic Attack?
A stroke is a medical emergency. When a stroke is suspected, emergency medical services should be activated (911 should be called in the U.S.). With the inability to predict the future, there is no way of knowing whether the symptoms will resolve. If the symptoms persist and a stroke situation exists, there is a narrow window of time to intervene and potentially use TPA (a clot-busting drug) to restore blood supply to the brain and reverse the neurologic deficits. Depending on the hospital and its capabilities, there may be only three to four and a half hours from the onset of symptoms in which to administer the drugs. In that time, the patient needs to be examined, blood tests need to be drawn, a CT scan of the head needs to be performed to insure that a hemorrhagic stroke (bleeding into the brain) is not the cause, and a neurologist needs to be contacted.
If EMS is not activated and the symptoms resolve so that the patient, family, or friends suspect that a TIA has occurred, there is still a need to seek care urgently. It may be reasonable to contact the primary care provider to help coordinate the evaluation.
How Is Transient Ischemic Attack (TIA) Diagnosed?
The diagnosis of TIA is most often made by history, since the neurologic deficits have most likely resolved before the patient presents for care. This history will also try to identify risk factors for heart disease and stroke:
Physical examination will include monitoring heart rate and rhythm and listening to the heart and lungs. Examination of the neck may include listening for bruits (abnormal sound made by blood rushing through narrowed blood vessels) or sounds made by blood rushing through narrowed blood vessels. A full neurologic exam will be undertaken and may include looking for weakness or numbness; assessing walk and coordination; and checking vision, hearing, speech, and language comprehension.
Other tests that may be considered include:
- Electrocardiogram (EKG) and monitoring to look for irregular heart rhythms like atrial fibrillation.
- CT scan of the head to look for bleeding in the brain. Strokes do not appear right away on a CT scan. It is a test to rule out bleeding, not to confirm a stroke or TIA.
- Carotid ultrasound is a test to look for narrowing of the blood vessels in the anterior part of the neck that provide the majority of blood supply to the brain.
Basic blood tests may include a CBC (complete blood count) to look for anemia or problems with too many or too few platelets. Patients who take warfarin (Coumadin) (a blood thinner to prevent blood clots from atrial fibrillation) will have their blood tested to make certain the medication dosage is appropriate.
If there is concern that there may be clots coming from the heart or debris coming from heart valves, then an echocardiogram (ultrasound examination of the heart) may be indicated to help with the diagnosis as to the origin of the TIA.
What Is the Treatment for Transient Ischemic Attack (TIA)?
Treatment of TIA is aimed at preventing a future stroke. Simple scoring systems have been developed to estimate this risk and help decide whether a patient should be admitted to the hospital for observation or whether they can be discharged home for observation.
ABCD and ABCD2 (diabetes is considered) scores are commonly used predictors.
ABCD2 Risk Assessment
|Risk Factor||Yes or No||Total Points|
|Age > 60||Yes|
|BP > 140/90 at initial reading||Yes|
|Clinical features of TIA:||Unilateral (one sided) weakness with or without speech impairment OR|
Speech disturbance without weakness
|Duration||60 minutes or more|
10 to 59 minutes
< 10 minutes
|ABCD2 Score||2 Day Stroke Risk|
|ABCD Score||7 Day Stroke Risk|
|6 or greater||31%|
What Is the Medical Treatment for Transient Ischemic Attack (TIA)?
Treatment of TIA is aimed at preventing a future stroke.
- Minimizing risk factors is a priority, including optimizing blood pressure, cholesterol and lipid levels, and controlling diabetes.
- Aspirin is the drug of choice to prevent future TIAs or stroke. Aspirin makes platelets less sticky and prevents clot formation.
- If the TIA occurs when the patient is already taking aspirin, then alternative anti-platelet drugs like clopidogrel bisulfate (Plavix) or aspirin-dipyridamole ER (Aggrenox) may be indicated.
- If the carotid ultrasound shows major narrowing of the artery (stenosis), referral to a vascular surgeon may be necessary to unclog the artery with a procedure known as carotid endarterectomy.
What Are the Next Steps in Caring for a Transient Ischemic Attack?
TIAs cannot be ignored since they are warning signs for a potential future stroke. Ten percent of people with TIAs will have a stroke within three months. The purpose of accessing medical care is to help minimize risk factors to help decrease that 10% risk. Published studies in 2007 suggest that if blood pressure is tightly controlled, cholesterol levels are reduced with medication, and smoking cessation is begun, the risk of future stroke can be reduced to 2%.
How Do I Prevent Transient Ischemic Attack (TIA)?
Minimizing risk factors is a life long endeavor. While we cannot pick our family members and control genetic disposition for heart disease and stroke, we can eliminate some risks like smoking, and minimize others like poorly controlled diabetes, high blood pressure, and high cholesterol. This prescription takes hard work and effort, but can help prevent narrowing of the arteries and the potential for TIA and stroke.
What Is the Prognosis for Transient Ischemic Attack (TIA)?
TIA should be considered a major warning sign of potential of stroke. The patient and primary care provider should work as a team to help prevent the occurrence of a devastating stroke.