Transient Ischemic Attack – Causes, Symptoms, Treatment

A Transient Ischemic Attack (TIA) is a medical emergency. It is defined as a transient episode of neurologic dysfunction due to the focal brain, spinal cord, or retinal ischemia?, without acute? infarction? or tissue injury. The definition of a TIA has moved from time-based to tissue-based. A TIA typically lasts less than an hour, more often minutes. TIA can be considered as a serious warning for an impending ischemic stroke?; the risk is highest in the first 48 hours following a transient ischemic attack. Differentiating transient ischemic attack from other mimicking conditions is important. Transient ischemic attacks are usually associated with a focal neurologic deficit and/or speech disturbance in a vascular territory due to underlying cerebrovascular disease. It is always sudden in onset.

A Transient Ischemic Attack (TIA), commonly known as a mini-stroke?, is a brief episode of neurological dysfunction caused by loss of blood flow (ischemia?) in the brain, spinal cord, or retina, without tissue death (infarction?). TIAs have the same underlying mechanism as ischemic strokes. Both are caused by a disruption in blood flow to the brain, or cerebral blood flow (CBF). The definition of TIA was classically based on duration of neurological symptoms. The current widely accepted definition is called “tissue-based” because it is based on imaging, not time. The American Heart Association and the American Stroke? Association (AHA/ASA) now define TIA as a brief episode of neurological dysfunction with a vascular cause, with clinical symptoms typically lasting less than one hour, and without evidence of infarction on imaging.^[rx]

Pathophysiology

The pathophysiology of TIA depends on the subtype as follows. The common issue is the transient interruption of arterial blood flow to an area of the brain supplied by that particular artery.

• Large artery atherothrombosis. This may be intracranial or extracranial atherothrombosis. The mechanism may be a lack of blood flow distal to the site of arterial stenosis? or an artery to artery embolism? which is actually the more common mechanism.
• Small vessel ischemic diseases. The underlying pathology is either lipohyalinosis or small vessel arteriolosclerosis. The commonest risk factor is hypertension? followed by insulin? is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">diabetes? and age.
• Cardiac embolism?. A clot in the cardiac chamber most commonly in the left atrium secondary to atrial fibrillation.
• Cryptogenic. This is usually a cortical pattern of ischemia? without any identifiable large artery atherothrombosis or cardiac source of emboli. More recently it is often referred to as ESUS (embolic stroke? of unknown source).
• Other uncommon causes such as arterial dissection or hypercoagulable states.

Causes of Transient Ischemic Attack

The most common underlying pathology leading to TIA and stroke? is a cardiac condition called atrial fibrillation, where poor coordination of contraction leads to a formation of a clot in the atrial chamber that can become dislodged and travel to a cerebral artery.^[rx][rx] Unlike in stroke?, the blood flow can become restored prior to infarction? which leads to the resolution of neurologic symptoms.^[rx][rx] Another common culprit of TIA is an atherosclerotic plaque? located in the common carotid artery, typically by the bifurcation between the internal and external carotids, that becomes an embolism? to the brain vasculature similar to the clot in the prior example. A portion of the plaque? can become dislodged and lead to embolic pathology in the cerebral vessels.^[rx]

TIA subtypes, classified according to the pathophysiological mechanisms are similar to ischemic stroke? subtypes. They include large artery

• atherothrombosis,
• cardiac embolism?,
• small vessel (lacunar),
• cryptogenic, and uncommon subtypes such as vascular dissection,
• vasculitis, etc.
• insulin? is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">diabetes?,
• hypertension?,
• age,
• smoking,
• obesity,
• alcoholism,
• unhealthy diet,
• psychosocial stress, and lack of regular physical activity.
• A previous history of stroke? or TIA will increase substantially the subsequent risk of recurrent stroke or TIA.[rx][rx] Among all risk factors, hypertension? is the most important one for an individual as well as in a population.

Symptoms of Transient Ischemic Attack

The main symptoms of a TIA can be remembered with the word FAST

• Face – the face may have dropped on 1 side, the person may not be able to smile, or their mouth or eye may have dropped.
• Arms – the person may not be able to lift both arms and keep them raised because of weakness? or numbness? in 1 arm.
• Speech – their speech may be slurred or garbled, or the person may not be able to talk at all, despite appearing to be awake; they may also have problems understanding what you’re saying to them.
• Time – it’s time to call 999 immediately if you see any of these signs or symptoms.
• Amaurosis fugax (painless, temporary loss of vision)
• One-sided facial droop
• One-sided motor weakness?
• Diplopia (double vision)
• Problems with balance and spatial orientation or dizziness
• Visual field deficits, such as homonymous hemianopsia or monocular blindness^[rx]
• Sensory deficits in one or more limbs and of the face^[rx]
• Loss of ability to understand or express speech (aphasia)
• Difficulty with the articulation of speech (dysarthria)
• Unsteady gait
• Difficulties with swallowing (dysphagia?)^[rx]

Other Possible Symptoms

The symptoms in the FAST test identify most strokes and TIAs, but a TIA can occasionally cause different symptoms that typically appear suddenly (usually over a few seconds).

Other signs and symptoms may include:

• complete paralysis of one side of the body
• sudden vision loss, blurred vision or double vision
• vertigo?
• being sick
• dizziness
• confusion
• difficulty understanding what others are saying
• problems with balance and co-ordination
• difficulty swallowing (dysphagia?)

Diagnosis of Transient Ischemic Attack

Several tests may be done to confirm a TIA and look for problems that may have caused it. Some of these tests include:

• Physical exam and tests. Your doctor will perform a physical exam and a neurological exam. The doctor will test your vision, eye movements, speech and language, strength, reflexes, and sensory system. Your doctor may use a stethoscope to listen to the carotid artery in your neck. A whooshing sound (bruit) may indicate atherosclerosis. Or your doctor may use an ophthalmoscope to look for cholesterol fragments or platelet fragments (emboli) in the tiny blood vessels of the retina at the back of your eye.
• Blood pressure tests – Your blood pressure will be checked because high blood pressure (hypertension) can lead to TIAs.
• Blood tests – You might need blood tests to check whether you have high cholesterol or diabetes.
• Electrocardiogram (ECG) – An electrocardiogram (ECG) measures your heart’s electrical activity using a number of electrodes (small, sticky patches) attached to your skin. An ECG can detect abnormal heart rhythms, which may be a sign of conditions such as where your heart beats irregularly (atrial fibrillation), which can increase your risk of TIAs.
• Carotid ultrasound – A carotid ultrasound scan can show if there is narrowing or any blockages in the neck arteries leading to your brain. A small probe (transducer) sends high-frequency sound waves into your body. When these sound waves bounce back, they can be used to create an image of the inside of your body.
• Carotid ultrasonography – If your doctor suspects that the carotid artery may be the cause of your TIA, a carotid ultrasound may be considered. A wand-like device (transducer) sends high-frequency sound waves into your neck. After the sound waves pass through your tissue and back, your doctor can analyze images on a screen to look for narrowing or clotting in the carotid arteries.
• Computerized tomography (CT) or computerized tomography angiography (CTA) scanning –  CT scanning of your head uses X-ray beams to assemble a composite 3D look at your brain or evaluate the arteries in your neck and brain. CTA scanning uses X-rays similar to a standard CT scan but may also involve injection of a contrast material into a blood vessel. Unlike a carotid ultrasound, a CTA scan can evaluate blood vessels in the neck and head.
• Magnetic resonance imaging (MRI) or magnetic resonance angiography (MRA). These procedures, which use a strong magnetic field, can generate a composite 3D view of your brain. MRA uses technology similar to MRI to evaluate the arteries in your neck and brain but may include an injection of a contrast material into a blood vessel.
• Echocardiography. Your doctor may choose to perform traditional echocardiography called a transthoracic echocardiogram (TTE). A TTE involves moving an instrument called a transducer across your chest. The transducer emits sound waves that bounce off different parts of your heart, creating an ultrasound image. Or your doctor may choose to perform another type of echocardiography called a transesophageal echocardiogram (TEE). During a TEE, a flexible probe with a transducer built into it is placed in your esophagus — the tube that connects the back of your mouth to your stomach. Because your esophagus is directly behind your heart, clearer, detailed ultrasound images can be created. This allows a better view of some things, such as blood clots, that might not be seen clearly in a traditional echocardiography exam.
• Arteriography. This procedure gives a view of arteries in your brain not normally seen in X-ray imaging. A radiologist inserts a thin, flexible tube (catheter) through a small incision, usually in your groin. The catheter is manipulated through your major arteries and into your carotid or vertebral artery. Then the radiologist injects a dye through the catheter to provide X-ray images of the arteries in your brain. This procedure may be used in selected cases.
• Brain scans – Brain scans are not always necessary if you‘ve had a TIA. They’re usually only done if it’s not clear which part of your brain was affected. An MRI scan is most often used. This type of scan uses a strong magnetic field and radio waves to create an image of your brain.

Treatment of Transient Ischemic Attack

Medicines

Most people who have had a TIA will need to take 1 or more medicines every day, long term, to help reduce their chances of having a stroke or another TIA.

Aspirin and other antiplatelet medicines

• You’ll probably be given aspirin straight after a suspected TIA. Aspirin works as an antiplatelet medicine. Platelets are blood cells that help blood to clot. Antiplatelet medicines work by reducing the ability of platelets to stick together and form blood clots. You may also be given other antiplatelets, such as clopidogrel or dipyridamole. The main side effects of antiplatelet medicines include indigestion and an increased risk of bleeding. For example, you may bleed for longer if you cut yourself and you may bruise easily.

Anticoagulants

Anticoagulant medicines can help to prevent blood clots by changing the chemical composition of your blood in a way that stops clots from forming.

• They’re usually offered to people who had a TIA that was caused by a blood clot in their heart. This is often due to a condition called atrial fibrillation, which causes your heart to beat irregularly.
• Warfarin, apixaban, dabigatran, edoxaban and rivaroxaban are examples of anticoagulants that may be offered to some people who have had a TIA.

A side effect of all anticoagulants is the risk of bleeding, because these medicines reduce the blood’s ability to clot. You may need regular blood tests while taking warfarin, so doctors can check your dose is not too high or too low.

Blood pressure medicines

If you have high blood pressure, you’ll be offered a type of medicine called an antihypertensive to control it. This is because high blood pressure increases your risk of having a TIA or stroke.

There are lots of different types of medicine that can help control blood pressure, including:

• thiazide diuretics
• angiotensin-converting enzyme (ACE) inhibitors
• calcium channel blockers
• beta-blockers

Your doctor will advise you about which antihypertensive is the most suitable for you. Some people may be offered a combination of 2 or more different medicines.

Statins

• If you have high cholesterol, you’ll be advised to take a medicine known as a statin. Statins reduce the level of cholesterol in your blood by blocking an enzyme in the liver that produces cholesterol.
• Statins may also help to reduce your risk of a stroke whatever your cholesterol level is. You may be offered a statin even if your cholesterol level is not particularly high.
• Examples of statins often given to people who have had a TIA include atorvastatin, simvastatin and rosuvastatin.
• There is inconsistent evidence regarding the effect of LDL-cholesterol levels on stroke risk after TIA. Elevated cholesterol may increase ischemic stroke risk while decreasing the risk of hemorrhagic stroke.^[rx][rx][rx]
• While its role in stroke prevention is currently unclear, statin therapy has been shown to reduce all-cause mortality and may be recommended after TIA.^[rx]

Blood pressure control

• Blood pressure control may be indicated after TIA to reduce the risk of ischemic stroke. About 70% of patients with recent ischemic stroke are found to have hypertension, defined as systolic blood pressure (SBP) > 140 mmHg, or diastolic blood pressure (DBP) > 90 mmHg.
• Until the first half of the 2010s, blood pressure goals have generally been SBP < 140 mmHg and DBP < 90 mmHg.^[rx] However, newer studies suggest that a goal of SBP <130 mmHg may confer even greater benefit.
• Blood pressure control is often achieved using diuretics or a combination of diuretics and angiotensin converter enzyme inhibitors, although the optimal treatment regimen depends on the individual.^[rx]

Diabetes control

• Diabetes mellitus increases the risk of ischemic stroke by 1.5-3.7 times, and may account for at least 8% of first ischemic strokes.^[rx] While intensive glucose control can prevent certain complications of diabetes such as kidney damage and retinal damage, there has previously been little evidence that it decreases the risk of stroke or death.^[rx] However, data from 2017 suggests that metformin, pioglitazone and semaglutide may reduce stroke risk.^[rx]

Surgery

In some cases, an operation called a carotid endarterectomy may be recommended after having a TIA.

Carotid endarterectomy

• A carotid endarterectomy involves removing part of the lining of the carotid arteries – the main blood vessels that supply the head and neck – plus any blockage inside the carotid arteries.
• When fatty deposits build up inside the carotid arteries, the arteries become hard and narrow, making it more difficult for blood to flow to your brain. This is known as atherosclerosis and can lead to TIAs and strokes if the blood supply to the brain becomes disrupted.
• By unblocking the carotid arteries when they have become moderately or severely narrowed, carotid endarterectomy can significantly reduce the risk of having a stroke or another TIA.

Health conditions

• High blood pressure – The risk of a stroke begins to increase at blood pressure readings higher than 140/90 millimeters of mercury (mm Hg). Your doctor will help you decide on a target blood pressure based on your age, whether you have diabetes and other factors.
• High cholesterol – Eating less cholesterol and fat, especially saturated fat and trans fat, may reduce the plaques in your arteries. If you can’t control your cholesterol through dietary changes alone, your doctor may prescribe a statin or another type of cholesterol-lowering medication.
• Cardiovascular disease – This includes heart failure, a heart defect, a heart infection or an abnormal heart rhythm.
• Carotid artery disease – The blood vessels in your neck that lead to your brain become clogged.
• Peripheral artery disease (PAD) – The blood vessels that carry blood to your arms and legs become clogged.
• Diabetes – Diabetes increases the severity of atherosclerosis — narrowing of the arteries due to accumulation of fatty deposits — and the speed with which it develops.
• High levels of homocysteine – Elevated levels of this amino acid in your blood can cause your arteries to thicken and scar, which makes them more susceptible to clots.
• Excess weight – Obesity, especially carrying extra weight in the abdominal area, increases stroke risk in both men and women.

Lifestyle choices

• Cigarette smoking – Quit smoking to reduce your risk of a TIA and a stroke. Smoking increases your risk of blood clots, raises your blood pressure and contributes to the development of cholesterol-containing fatty deposits in your arteries (atherosclerosis).
• Physical inactivity – Engaging in 30 minutes of moderate-intensity exercise most days helps reduce risk.
• Poor nutrition – Reducing your intake of fat and salt decreases your risk of a TIA and a stroke.
• Heavy drinking – If you drink alcohol, limit yourself to no more than two drinks daily if you’re a man and one drink daily if you’re a woman.
• Use of illicit drugs – Avoid cocaine and other illicit drugs.

Prevention

Knowing your risk factors and living healthfully are the best things you can do to prevent a TIA. Included in a healthy lifestyle are regular medical checkups. Also:

• Don’t smoke – Stopping smoking reduces your risk of a TIA or a stroke.
• Limit cholesterol and fat – Cutting back on cholesterol and fat, especially saturated fat and trans fat, in your diet may reduce the buildup of plaques in your arteries.
• Eat plenty of fruits and vegetables – These foods contain nutrients such as potassium, folate and antioxidants, which may protect against a TIA or a stroke.
• Limit sodium – If you have high blood pressure, avoiding salty foods and not adding salt to food may reduce your blood pressure. Avoiding salt may not prevent hypertension, but excess sodium may increase blood pressure in people who are sensitive to sodium.
• Exercise regularly – If you have high blood pressure, regular exercise is one of the few ways you can lower your blood pressure without drugs.
• Limit alcohol intake – Drink alcohol in moderation, if at all. The recommended limit is no more than one drink daily for women and two a day for men.
• Maintain a healthy weight – Being overweight contributes to other risk factors, such as high blood pressure, cardiovascular disease and diabetes. Losing weight with diet and exercise may lower your blood pressure and improve your cholesterol levels.
• Don’t use illicit drugs – Drugs such as cocaine are associated with an increased risk of a TIA or a stroke.
• Control diabetes – You can manage diabetes and high blood pressure with diet, exercise, weight control and, when necessary, medication.

References