A Transient Ischemic Attack (TIA) is a phenomenon caused by a temporary disruption in the blood supply to part of the brain. Unlike a stroke, the circulatory blockage is brief and there is no brain tissue death (i.e. permanent damage) as the blockage breaks away and dissolves.
A TIA is similar to a stroke and results in stroke-like symptoms but these tend to last for only a few minutes or 1-2 hours before fully resolving within 24 hours.
In the days following a TIA, the risk of a stroke increases dramatically; in fact, a third of the people with TIA later have recurrent TIAs and a third have a stroke in the future. Fortunately, one may also consider the occurrence of a TIA as an opportunity to find a cause or minimize the risk to prevent a possible stroke.
A TIA is characterized by a disrupted blood supply to a region of the brain which very commonly results due to blood clots. These can form in the arteries of the brain (thrombosis) usually following the gradual narrowing of the blood vessel by plaque (a fatty build up) in a process called atherosclerosis. A blood clot can form if the plaque ruptures, leading to further blockage of the artery.
If a person is suffering from atrial fibrillation, blood clots may float downstream from the heart and get caught in small blood vessels (embolus). Atrial fibrillation is characterized by an uncoordinated heart beat which allows blood to become stagnant and form small clots that can embolize to any organ in the body, such as the brain.
Due to the complexity of structure and function of the brain, the resulting deficits are grouped based on the anatomy of the brain.
- Paralysis of different limbs depending on affected brain region.
- Difficulty in speech or understanding.
- Numbness of a limb (particularly on one side of the body).
- Clumsiness during walking or with certain hand movements.
- Lack of balance and coordination.
- Severe headache.
- Age. Risk increases with age, particularly after age 55.
- Sex. The risk of both TIA and stroke is slightly higher in males than in females
- Prior or family history of TIA. Prior TIA makes one 10 times more likely to have a stroke and the risk may generally be greater if a family member has suffered from a TIA or stroke.
- Poor nutrition. High fat and salt intake, in particular, increase your weight and contribute to your risk of TIA and stroke. Reducing saturated fat and trans fats intake may reduce the plaques in arteries. However, if dietary changes alone do not help, cholesterol-lowering medication may be prescribed (e.g. statins).
- Cardiovascular disease. This includes heart failure, heart defects, heart infections or abnormal heart rhythm.
- Diabetes. This increases the severity of atherosclerosis and the speed of its progression.
- Elevated homocysteine levels. This amino acid in the blood can cause arteries to thicken and scar, thereby increasing the susceptibility to clots.
- Smoking. Cigarette smoking increases the risk of blood clots, elevates blood pressure and contributes to the development of atherosclerosis.
- Alcohol abuse. Alcohol intake should be limited to a maximum of two drinks daily for a man and one drink daily for a woman.
Following a TIA, common tests may be done which include:
- An angiogram to determine if there is vessel blockage or bleeding.
- An ultrasound to check for the narrowing of arteries e.g. carotid arteries.
- An echocardiogram (echo) to check the blood flow through the heart and check if there are any blood clots.
- An electrocardiogram (ECG) and heart rhythm tests to ensure a regular heartbeat.
- Cholesterol and triglycerides tests – when elevated, these increase the risk of blood clots and atherosclerosis.
Importantly, while a head CT scan or brain MRI will almost always be ordered, a stroke may show changes where a TIA will not.