Occipital Stroke and Anton Syndrome

Anton syndrome is a rare condition found in people who have lost their vision after brain damage to the occipital lobes. The main characteristic of Anton syndrome is that these patients do not realize that they are blind.

It occurs most often in patients who have had an occipital stroke. However, Anton syndrome can also be a complication of other diseases that impact the brain.

This article provides more information about the symptoms, causes, diagnosis, and treatment of Anton syndrome.

Symptoms

Symptoms of Anton syndrome include:

• Vision loss
• Visual anosognosia, which means the person is unaware of being blind
• Confabulations, or presenting false memories of seeing something that wasn't there

Patients with Anton syndrome will deny that they are blind despite evidence to the contrary. They will act as though they are not actually blind.

For example, if you held an object and asked what it is, they might answer confidently with a guess. They would 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.

Even though this behavior may seem puzzling, they believe they are correct. Their brain is simply unable to figure out that they are blind.

Causes

Anton syndrome is caused by damage to the brain in the occipital lobe, which is in the back of the brain. The occipital lobe allows you to see as well as interpret what you're seeing.

One of the main causes of Anton syndrome is a stroke. This is a medical emergency where blood flow to the brain is interrupted by a ruptured artery or a blood clot. When any part of the brain is deprived of oxygen, brain cells in that area begin to die.

When the occipital lobes of the brain are completely affected by a stroke, the end result is a phenomenon called “cortical blindness.” "Cortical" refers to damage in the brain's surface layers in the occipital lobe.

When damage to the occipital lobe causes blindness, it could also result in Anton syndrome. However, Anton syndrome is considered a rare condition.

It's unknown exactly how Anton syndrome develops, however, often there is a history of cognitive impairment.

One theory is that patients with damage to the primary visual cortex (the part of the brain that processes visual signals) also have damage to the visual association cortex (a part that connects those signals to other parts of the brain that help interpret them). That may cause the lack of awareness of their blindness.

While stroke is the most common cause of Anton syndrome, it can occur with other conditions that cause damage to the occipital lobe. These include:

• Trauma
  
• Multiple sclerosis
• Hypertensive encephalopathy (high blood pressure causes brain dysfunction)
• Brain tumors

Diagnosis

To help diagnose your condition, your healthcare provider will typically start with a physical examination.

They may see if your eyes can follow a light. They'll talk to you about your sight to get a sense of your awareness of your vision loss. If they suspect the development of Anton syndrome, they'll likely order an urgent workup including imaging tests to help look for damage in the occipital lobe. 

Tests may include a head computed tomography (CT) scan or magnetic resonance imaging (MRI).

Treatment

Treatment for Anton syndrome will depend on what caused the damage to the occipital lobe. For example, in rare cases where multiple sclerosis causes brain damage, treatment will focus on treating the MS. This may include intravenous methylprednisolone.

If Anton syndrome was caused by a stroke, therapy would focus on preventing another stroke from causing more damage. This may include medications, such as daily aspirin or statins, and managing risk factors such as blood pressure and glucose (blood sugar) levels.

In some cases, vision may improve with treatment. This often depends on the patient's age and health condition. Someone who's younger, didn't have a stroke, and has no history of hypertension (high blood pressure) or diabetes may be more likely to see improvement.

While improvement of Anton syndrome is less likely after having a stroke, treatment will likely focus on preventing future cardiovascular events.

Summary

Anton syndrome is a rare condition in which the patient loses their sight but doesn't recognize that they're blind. It's caused by damage in the brain's occipital lobe, usually from a stroke but rarely from other conditions. Treatment focuses on the condition that caused the damage to the brain.