People at risk and partners or caretakers of people at risk for stroke should be aware of the general symptoms, and the stroke victim should get to the hospital as soon as after these warning signs appear. Discouragingly, a 2001 study reported that over 30% of patients with either a stroke or TIA who called their primary care physician were neither evaluated nor sent to the hospital within a month after the first event.

It is particularly important for people with migraines or frequent severe headaches to understand how to distinguish between their usual headaches and symptoms of stroke.

Transient Ischemic Attacks (TIAs)
TIAs are mini-ischemic strokes, usually caused by tiny emboli (often formed of pieces of calcium and fatty plaque) that lodge in an artery to the brain. They typically break up quickly and dissolve but they do temporarily block the supply of blood to the brain. The mental or physical disturbances resulting from TIAs generally clear up in less than a day, with nearly all symptoms resolving in less than an hour. Because blood supply is quickly restored to the brain, there is no residual damage as there is in a full-blown stroke.

Transient ischemic attacks, however, are the warning signals of ischemic stroke, just as angina (chest pain caused by coronary artery disease) is the red flag for a heart attack. About 5% of those who experience TIAs go on to suffer a stroke within a month, and without treatment, a third will have strokes within five years. (Because of the relationship between atherosclerosis, coronary artery disease, and stroke, TIAs are also warning signs for a heart attack.)

One of two major arteries is usually involved in a transient ischemic attack, either the carotid or basilar arteries:

Symptoms of TIAs in the Carotid Arteries. The carotid arteries stem off of the aorta (the primary artery leading from the heart) and lead up through the neck around the windpipe and on into the brain. When TIAs occur from blockage in the carotid artery, which they often do, symptoms may occur in either the retina of the eye or the cerebral hemisphere (the large top part of the brain):

 
• When oxygen to the eye is reduced, people describe the visual effect as a shade being pulled down. People may develop poor night vision.  
• When the cerebral hemisphere is affected by a TIA, a person can experience problems with speech and partial and temporary paralysis, tingling, and numbness, usually on one side of the body.

Symptoms of TIAs in the Basilar Artery. The other major site of trouble, the basilar artery, is formed at the base of the skull from the vertebral arteries, which run up along the spine and join at the back of the head. When TIAs occur here, both hemispheres of the brain may be affected so that symptoms occur on both sides of the body. Some include the following:

 
• Temporarily dim, gray, blurry, or lost vision in both eyes.  
• Tingling or numbness in the mouth, cheeks, or gums.  
• Headache in the back of the head.  
• Dizziness.  
• Nausea and vomiting.  
• Difficulty swallowing.  
• Inability to speak clearly.  
• Weakness in the arms and legs, sometimes causing a sudden fall.

Symptoms of Major Ischemic Stroke
Speed of Symptom Onset. The speed of symptom onset of a major ischemic stroke may indicate its source:

 
• If the stroke is caused by a large embolus (a clot that has traveled to an artery in the brain), the onset is sudden. Headache and seizures can occur within seconds of the blockage.  
• When thrombosis (a blood clot that has formed within the brain) causes the stroke, the onset usually occurs more gradually, over minutes to hours. On rare occasions it progresses over days to weeks.

Symptoms. The symptoms for a major ischemic stroke are extremely variable:

 
• Early symptoms can be identical to those of a transient ischemic attack, since, in both cases, the clot can produce a blockage in a branch of the carotid or basilar arteries. (In the case of a TIA, however, the symptoms resolve.) [ See above. ]  
• The blood clot usually affects the opposite side of the body from its location in the brain, with possible loss of feeling on one side of the face, in an arm or leg, or blindness in one eye.  
• Speech problems can occur if the left hemisphere of the brain is involved. (In some people, mostly those who are left-handed, speech can be affected by a clot on the right side of the brain.) The stroke victim may be unable to express thoughts verbally or to understand spoken words.  
• Patients may experience major seizures and possibly coma.

Symptoms of Hemorrhagic Stroke
Cerebral Hemorrhage Symptoms. Symptoms of a cerebral, or parenchymal, hemorrhage typically begin very suddenly and evolve over several hours and include:

 
• Headache.  
• Nausea and vomiting.  
• Altered mental states.

Subarachnoid Hemorrhage. When the hemorrhage is a subarachnoid type, warning signs may occur from the leaky blood vessel a few days to a month before the aneurysm fully develops and ruptures. Warning signs may include:

 
• Abrupt headaches.  
• Nausea and vomiting.  
• Sensitivity to light.  
• Various neurologic abnormalities.

When the aneurysm ruptures, the stroke victim may experience the following:

 
• A terrible headache.  
• Neck stiffness.  
• Vomiting.  
• Altered states of consciousness.  
• The eyes may become fixed in one direction or lose vision.  
• Stupor, rigidity, and coma.

Silent Brain Infarctions
As many as 31% of the elderly experience silent brain infarctions, which are small strokes that cause no apparent symptoms but are major contributors to mental impairment in the elderly. Smokers and people with hypertension are at particular risk.