Anton Syndrome

What is Anton Syndrome?

Elderly woman looking out window
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Anton Syndrome is a peculiar symptom of an occipital stroke, or other forms of brain damage in that area. It causes complete blindness.

What Is a Stroke?

Stroke is a disease that affects the arteries leading to and within the brain. It is theNo. 5 cause of death and a leading cause of disability in the United States. 

A stroke occurs when a blood vessel that carries oxygen and nutrients to the brain is either blocked by a clot or bursts (or ruptures).

When that happens, part of the brain cannot get the blood (and oxygen) it needs, so it and brain cells die.

Stroke Affecting the Occipital Pole

The occipital pole is the area of the brain where central vision is processed.

By central vision, we mean what you see at the center of the visual field when you are looking straight ahead. Therefore, a stroke there would cause you to have a large blind spot in the very middle of your visual field on the affected side.

A person with such a deficit may have trouble looking straight ahead at someone’s face, as she may not be able to see the person's nose, upper lip, and the lower half of the eye on the affected side, but they could see the shoulder and the top of their head on that side. Thankfully, these strokes are rare, but when they do occur the visual problem that arises is called “central visual defect.”

Stroke Affecting the Occipital Lobes on Both Sides – 'Cortical Blindness'

When the occipital lobes of the brain are completely affected by a stroke, the end result is a phenomenon called “cortical blindness.” In essence this is the same as what we all understand by the term “blindness,” but doctors use this term in order to convey to each other that the specific reason for blindness in that person is damage to the brain cortex.

People with cortical blindness sometimes also suffer from a condition called visual anosagnosia. Another name for this is Anton syndrome.

Anton Syndrome

After the injury to the occipital lobe, the person acts as though he/she is not actually blind. If you were to place a spoon in front of their eyes and ask them to choose whether what you are holding is a spoon, a pen, or a watch, they would answer confidently with a guess and act as though that was the correct answer, even if they are wrong.

If you ask them to describe what they are seeing, they will make up a whole visual scenario for you.

They even try to walk as though they were not blind and end up colliding with objects in their path. What is really interesting is that they are not lying to you. Their brain is simply unable to figure out that they are blind. 

References:

Allan Ropper and Robert Brown, Adam's and Victor's Principles of Neurology, 8th Edition McGraw-Hill Companies Inc, United States of America, 2005, pp 417-430.

American Stroke Association. http://www.strokeassociation.org/STROKEORG/

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