Posterior cortical atrophy

Posterior cortical atrophy (PCA) is a rare kind of dementia that starts in the back of the brain. This is the part that makes sense of what the eyes see. The eyes themselves are often healthy. But the brain has growing trouble reading, judging distance, or finding things in plain view.¹

Many people see an eye doctor first. The eye exam is often normal, so the real cause can be missed for a long time.^1,5

What is posterior cortical atrophy?

"Posterior" means the back. The "cortex" is the brain's wrinkled outer layer. "Atrophy" means shrinking. So PCA is a slow loss of brain cells in the back of the brain's outer layer.¹

These areas turn signals from the eyes into a picture you can use. They help you see where things are, how far away they are, and how they fit together. They also help with reading, writing, numbers and telling left from right.²

PCA is also called Benson's syndrome. Some experts call it the "visual variant" of Alzheimer's disease.

How common is it, and who gets it?

No one knows exactly how many people have PCA. It is often missed or mislabeled. Some studies suggest about 5 in 100 people diagnosed with Alzheimer's have PCA. The true number may be as high as 15 in 100.¹

It most often begins between ages 50 and 65.¹ A 2024 study gathered data on 1,092 people with PCA from 16 countries. Their average age when symptoms began was about 59. About 6 in 10 were women.³ So PCA is often a form of young-onset dementia (dementia that starts before age 65).

Older adults can get PCA too. In later life, vision complaints are easy to blame on cataracts, glaucoma or other eye disease. This can delay the right diagnosis even longer.

Early signs: what PCA looks like

Symptoms differ from person to person and change slowly over time.^1,4 Early on, a person may notice:

• Trouble reading. Losing their place, skipping lines, or seeing words as jumbled. This is one of the most common first complaints.⁵
• Misjudging distance. Bumping into door frames, missing a chair, or having trouble with stairs and curbs.^1,5
• Not seeing what is in plain view. Looking right at the salt shaker but not finding it. This is called simultanagnosia (seeing only one part of a scene at a time).²
• Trouble with moving objects. Struggling to tell if a car is moving or parked.^1,4
• Problems with driving, such as parking, staying in a lane or judging gaps.^4,5
• Trouble using tools and everyday objects, or getting dressed (for example, putting an arm in the wrong sleeve).^2,4
• Trouble with writing, spelling or simple math.^1,4
• Mixing up left and right.^2,4
• Trouble recognizing faces or objects by sight.⁴
• Getting lost in familiar places.⁵
• Anxiety. Many people feel worried or on edge as daily tasks become harder.¹

Some people see things that are not there (hallucinations).¹ In many people, memory and conversation stay fairly good at first. Memory problems may come later as the disease spreads.^1,2

Why it is often mistaken for eye disease

Many people with PCA first go to an optometrist or ophthalmologist. They describe blurry vision, glare or trouble reading. The eye exam often looks normal.^1,5 A neurology review noted that some people even have cataract surgery that does not fix the problem.⁵

Clues that point to the brain rather than the eyes include:^1,2,5

• Vision problems that slowly get worse while eye tests stay normal or mostly normal
• Trouble with tasks that need the brain to put a picture together, like reading a full page or finding objects on a busy table
• Trouble on color-dot vision tests, even though the person can still name colors⁵
• Loss of the same side of the visual field in both eyes, which can show up on a visual field test^2,5
• Memory that is still fairly good
• Symptoms that start between 50 and 65

If this sounds familiar, ask the eye doctor directly: "Could this be coming from the brain?" Ask for a referral to a neurologist, a memory clinic, or a neuro-ophthalmologist (an eye doctor trained in brain-related vision problems). See which specialist to see.

What causes PCA?

PCA is a pattern of symptoms, not one single disease. In 2017, an international group of experts agreed on shared criteria for PCA. They listed the diseases that can cause it:²

The 2024 study of 1,092 people found strong links to Alzheimer's:³

• About 94 in 100 people who had an amyloid PET scan showed amyloid (a sticky protein that builds up between brain cells).
• About 97 in 100 who had a tau PET scan showed tau (a protein that forms tangles inside brain cells).
• Among people studied after death, about 94 in 100 had Alzheimer's as the main brain disease. Many also had other changes, such as Lewy bodies or blood vessel damage.

The authors concluded that PCA is a strong sign of Alzheimer's disease, usually in a younger person.³ Experts still discuss whether to see PCA as a form of Alzheimer's or as its own condition.¹

Genes and risk. No clear gene mutation has been tied to PCA. It is not known whether the usual risk factors for Alzheimer's also raise the risk of PCA.¹ Read more on genes and dementia.

How doctors diagnose it

There is no single test for PCA. Doctors put together several pieces:^1,2

1. A full eye exam to rule out problems in the eyes or the nerves that carry signals from the eyes.
2. A history from the person and a family member. What changed, when, and how it affects daily life.
3. A neurological exam and thinking tests. A neuropsychologist may test reading, drawing, spatial skills, numbers and memory. See memory and thinking tests.
4. Blood tests to rule out other medical causes.
5. Brain scans. An MRI often shows shrinking in the back of the brain. PET scans can show low brain activity there, or show amyloid and tau. See brain scans.
6. Spinal fluid or blood tests for Alzheimer's in some cases, to check for amyloid and tau. See spinal fluid tests and blood tests for Alzheimer's.

Doctors must also rule out a stroke, a brain tumor or other causes that can look similar.^1,2 The experts' criteria say the problems should come on slowly, get worse gradually, and affect daily life.²

A memory clinic that sees many types of dementia is a good place to look. Our page on getting a dementia diagnosis explains the steps.

Treatment: what can and cannot help

There is no treatment yet that stops or slows PCA.¹ Care focuses on easing symptoms and making daily life safer and easier.

Memory medicines. Doctors sometimes try the Alzheimer's medicines called cholinesterase inhibitors, such as donepezil. They may help people whose PCA is caused by Alzheimer's or Lewy body disease. But they have not been well tested in PCA.^1,5 Limited research

New anti-amyloid drugs. Lecanemab and donanemab remove amyloid from the brain. They were tested mostly in people with typical, memory-first Alzheimer's. Expert advice for lecanemab says people with PCA caused by Alzheimer's may be candidates. It also says the safety and benefit in PCA have not been studied.⁷ Doctors should tell families about this gap. See are anti-amyloid treatments right for us?

Mood. Anxiety and low mood are common. Treating them may help some people, although this has not been well studied in PCA.¹ See anxiety and depression. Talk with your doctor or pharmacist before changing any medicine.

Therapy and rehabilitation. A neurology review suggests a referral to a low-vision center, occupational therapy and physical therapy.⁵ An occupational therapist can suggest tools and new ways to do daily tasks. A physical therapist can help with balance and walking. Limited research

Clinical trials. Some research centers study PCA. See joining a dementia clinical trial.

Daily life: practical changes that help

Small changes to the home can make a big difference. These tips come from the UCSF Memory and Aging Center:⁶

Talking books. Reading print often becomes hard early. The Library of Congress runs a free audiobook and braille library by mail. People can qualify if a visual or perceptual disability keeps them from reading regular print, even when an eye chart test is normal. A doctor, nurse, therapist, social worker or librarian can sign the form.⁸

Helping without taking over. Say where things are in words, such as "your cup is on your right." Offer your arm on stairs. Let the person do what they still can, and include them in decisions.

More ideas: making the home safer, preventing falls, technology that helps and eating and drinking.

Driving, work and planning ahead

Driving. Judging distance and seeing moving objects are needed for safe driving. These skills are often affected early in PCA.^4,5 A driving check may be needed soon after diagnosis, even if memory is still good. See driving and dementia.

Work and money. PCA often starts during working years. If the person cannot keep working, see Social Security disability for young-onset dementia.

Legal planning. Writing can become hard early in PCA.² It is wise to sign a durable power of attorney and an advance directive while the person can still make and express choices.

How PCA changes over time

PCA gets worse slowly. Over time, it often spreads to other parts of the brain. Memory, language and thinking may then decline in ways that look more like typical Alzheimer's.^1,5 How fast this happens differs a lot between people. See stages of dementia for what later stages can bring.

Questions to ask the doctor

Is this my eyes or my brain?

• My eye exam is normal. Could my vision problems come from the brain?
• Should I have a visual field test or see a neuro-ophthalmologist?
• Should I see a neurologist or a memory clinic?

What is causing my PCA?

• Is it most likely Alzheimer's disease, or something else?
• Do I need an MRI, PET scan, spinal fluid test or blood test to find out?
• What would the answer change about my care?

What can help now?

• Could a memory medicine help me? What are the side effects?
• Am I a candidate for an anti-amyloid drug or a clinical trial?
• Can you refer me to occupational therapy, low-vision services or physical therapy?
• Is it still safe for me to drive?

When to get help

See a doctor soon if you or someone you love has vision problems that keep getting worse, but glasses and eye exams do not explain them. Bring a family member to describe the changes. Ask for a referral to a neurologist or memory clinic.

The Alzheimer's Association 24/7 Helpline at 800-272-3900 can answer questions and help you find local support.¹ For the caregiver's own health, see caregiver burnout. For an overview of other types, return to types of dementia.

Education only. This page is general information written from the sources listed. It is not medical, legal or financial advice and does not replace a doctor, therapist or lawyer who knows your situation. How we write and check pages.