Doctor's Notes on Transient Ischemic Attack
Transient ischemic attack (also termed a TIA or mini-stroke) is when an area the brain has its blood supply interrupted and produce symptoms of stroke that usually resolve quickly within a few minutes up to 24 hours as the blood supply interruption resolves. A TIA is also a warning sign of possible future strokes. The signs and symptoms of a TIA are virtually identical to those of a stroke except that the symptoms resolve. Signs and symptoms of a TIA are neurological deficits that can affect the ability to move or feel on one side of the body, speech and vision can be affected and the person may experience confusion, difficulty seeing words and have the inability to follow commands; they also may develop dizziness, loss of balance and/or coordination, difficulty walking, a sudden fall (drop attack) and a sudden loss of vision in one eye that results spontaneously (amaurosis fugax).
The cause of transient ischemic attacks is an intermittent decrease or stoppage of blood and oxygen to brain cells; this blockage can originate from blood clot formation, debris from occluded blood vessels outside of the brain (for example, a carotid artery with plaque deposits) and by pressure on the brain’s blood vessels caused by some bleeding within the brain. For TIAs, these causes resolve spontaneously within minutes to 24 hours.
Transient Ischemic Attack
(TIA, Mini-Stroke) Symptoms
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).
Transient Ischemic Attack
(TIA, Mini-Stroke) Causes
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.
When the brain’s blood supply is inadequate, a stroke results. Stroke symptoms (for example, loss of arm or leg function or slurred speech) signify a medical emergency because without treatment, blood-deprived brain cells quickly become damaged or die, resulting in brain injury, serious disability, or death. Call 9-1-1 if you notice stroke symptoms developing in someone.
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.