Ask Dr. Pat

Dr. Pat Consults: The Anatomy of a Stroke

What are the signs and symptoms?

Strokes can cause any number of problems with speech, movement, feeling, coordination, or vision. The most commonly noticed symptoms are a facial droop, difficulty speaking or understanding, weakness and/or numbness on one side of the body, or loss of vision. Unfortunately, stroke victims are not always aware of the problem, as the brain controls both the various functions of the body as well as the ability to comprehend what is happening. In some specific cases, usually involving a part of the brain called the parietal lobe, patients will frankly deny that anything is wrong at all, and may not recognize part of their body as their own.

Different combinations of symptoms are associated with blockages in various arteries:

  • The middle cerebral artery (MCA) supplies blood to the part of the brain that controls feeling and movement in the arm and face. Blockages in the right MCA cause symptoms to occur on the left side of the body. Blockages in the left MCA cause symptoms to occur on the right side of the body, as well as causing difficulty speaking and understanding.
  • The anterior cerebral artery (ACA) supplies blood to the part of the brain that controls the legs. Blockages in the right ACA cause weakness in the left leg; blockages in the left ACA cause weakness in the right leg.
  • The posterior cerebral artery (PCA) supplies blood to the part of the brain that processes vision. Blockages in the right PCA cause loss of vision to the left side —not the left eye, but simply the left half of the world (see note below); blockages in the left PCA cause loss of vision to the right side.
  • The basilar and vertebral arteries supply blood to the brain stem and the cerebellum. Strokes in these arteries can cause weakness or numbness on either side of the body, incoordination, dizziness or “vertigo,” nausea and vomiting, trouble speaking or swallowing, and impairments in eye movement.
  • Small-artery strokes can occur in many different parts of the brain, but most commonly in deep structures of the brain called the basal ganglia, thalamus, internal capsule, as well as the brain stem. Because these strokes can occur in so many different parts of the brain, the symptoms are quite varied. The most common is a “pure motor stroke,” which occurs in about one third to one half of these strokes, and causes weakness in one side of the body. The second most common is an “ataxic hemiparesis” stroke, leaving a part of the body (usually the leg) weak and clumsy.

What Should You Do?

If you suspect that you or someone you know is having a stroke, it is important to get medical care immediately. Do not take any medications, do not take your blood pressure. Call 911 immediately, and come to the hospital. The American Heart Association and American Stroke Association recommends that you follow a simple acronym:


F – Face Drooping—Does one side of the face droop, or is it numb? Ask the person to smile. Is the person’s smile uneven?

A – Arm Weakness—Is one arm weak or numb? Ask the person to raise both arms. Does one arm drift downward?

S – Speech Difficulty—Is speech slurred? Is the person unable to speak or hard to understand? Ask the person to repeat a simple sentence, like “The sky is blue.” Is the sentence repeated correctly?

T —Time to call 911. If someone shows any of these symptoms, even if the symptoms go away, call 911 and get the person to the hospital immediately. Check the time, so you’ll know when the first symptoms appeared.

While this article does not cover all of the symptoms of stroke, it does cover the most common symptoms. Other signs and symptoms to look out for include confusion, sudden changes in vision, difficulty walking, balancing, or coordinating movements, or a sudden, unexplainable headache. Time is the most important factor in determining if the person having a stroke will be a candidate for an emergent intervention. Do not wait.

Note: The processing of visual information is a complex process. Light hits the back of both eyes, causing signals to travel back toward the brain through the optic nerves. These signals mix together as they pass through a structure called the optic chiasm. Here, the signals from both eyes that capture information from the left side of the world go to the right side of the brain (to the right cortex), and vice-versa for signals from the right side of the world. You can find a diagram of this process here.

Dr. Baxter Allen

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  • roz warren February 2, 2015 at 8:46 pm

    Terrific information. Thanks.

  • Andrea February 2, 2015 at 7:40 am

    Very informative article. When my elderly dad says “I’m fine Im fine ” I will use the F A S T rule for sure. Thank you Dr Allen. The apple obviously does not fall far from the tree!!