What is Posterior Cortical Atrophy?
Posterior cortical atrophy (PCA) is a rare and complex condition that progressively damages particular areas in the brain, primarily the back part, which affects vision and spatial awareness as well as practical skills and literacy. It usually starts showing symptoms between the ages of 50 to 65. The term ‘posterior cortical atrophy’ was first used in 1988 to describe issues with advanced visual processing, similar to two conditions called Gerstmann and Balint syndromes, but with a largely unaffected memory.
While PCA is often associated with Alzheimer’s disease, it actually presents as its own unique medical condition and primarily affects vision instead of memory. Indeed, patients suffering from PCA generally maintain good memory, language skills, and awareness, despite advanced damage in the back parts of their brain as shown on a brain MRI scan, which is more than commonly seen in standard Alzheimer’s disease cases.
What Causes Posterior Cortical Atrophy?
Alzheimer’s disease (AD), is often found to be the main cause of Posterior Cortical Atrophy (PCA), which is why PCA is sometimes referred to as a ‘visual variant’ of Alzheimer’s disease. Other lesser common diseases are also associated with PCA such as Lewy body disease, corticobasal degeneration, and a type of Creutzfeldt-Jakob disease called Heidenhain variant.
In 2017, new guidelines were established for diagnosing and classifying PCA. Using these guidelines, doctors are able to classify PCA into different categories such as PCA-pure, PCA-plus, and other types depending on how the disease presents itself and what the underlying cause might be. This helps doctors and researchers to better understand and manage PCA in a range of different situations.
Risk Factors and Frequency for Posterior Cortical Atrophy
Posterior cortical atrophy, a relatively rare brain disorder, typically starts to affect people before they turn 65. An study involving 302 patients from across the globe showed that most people are diagnosed between the ages of 50 and 65, with fewer cases reported amongst older individuals. The average age when people start experiencing this condition is almost 59. However, it’s tricky to pin down exactly how common this disorder is, as definitions have changed over time and it remains unusual.
- The diagnosis of posterior cortical atrophy depends on various clinical factors, showing up in about 5% of patients in specialty cognitive clinics.
- When considering early-onset Alzheimer disease data, this figure can rise to 13%.
- Some research suggests that this disorder is more common in women, reflecting that Alzheimer’s itself tends to be more common in women, while others do not report any significant difference between the sexes.
Signs and Symptoms of Posterior Cortical Atrophy
Posterior cortical atrophy is a medical condition that usually starts causing gradual disruption of the central vision, without affecting the peripheral vision. Often, patients experience symptoms for months or even years before being properly diagnosed, usually with around a four-year gap. In the early stages, people generally reach out to eye specialists, known as optometrists/ophthalmologists. It is relatively common for them to have had unsuccessful corrections to their eyeglasses or even undergone surgical procedures in an attempt to correct their symptoms. Anxiety could be an early sign of the disease.
Digging deeper into patients’ functioning, they may struggle with judging distances and the speed of traffic while driving. Patients often have trouble reading analog clocks and digital pixelated signs, and bumping into door frames or finding door knobs might be common, due to visual disorientation. As a result, they may also express unease when descending escalators and dealing with revolving doors. Experiencing significant difficulty reading poorly formed letters and numbers compared to the same when well-formed is strongly indicative of a condition known as apperceptive agnosia.
Patients may display symptoms of a series of medical conditions such as acalculia (difficulty with calculations), agraphia (trouble writing) and left-right disorientation, collectively known as Gerstmann syndrome. They may also exhibit Balint syndrome, characterized by difficulty coordinating eye movements, impaired hand-eye coordination, and inability to perceive the visual field as a whole. Most patients often demonstrate elements of these syndromes in the early stages of the disease. They usually fail to perceive a picture in its entirety and only see specific features.
One common finding with such patients is their significant inability to describe a complex picture as a whole, known as simultanagnosia. These individuals have problems focusing their visual attention, leading to “partonomic” errors and only noticing specific aspects of an object. Patients usually aren’t able to read particular color plates, despite having normal color vision, or find it challenging to interpret specific types of figures.
Neurological examinations may not reveal significant findings. However, some patients may have mild walking irregularities due to balance problems linked to visual processing difficulties. A small number of these patients may also demonstrate symptoms such as involuntary muscle movements or signs of motor disorders. Symptoms associated with a condition known as Lewy body disease, and the presence of dystonia, dyspraxia, myoclonus, alien limb could signal an underlying disorder called corticobasal degeneration.
Crutch et al. describe this condition as a gradual-onset syndrome with visual disturbances being significant early symptoms. Typical cognitive features include perception deficits, simultanagnosia, object perception issues, constructional dyspraxia, environmental agnosia, oculomotor apraxia, dressing apraxia, optic ataxia, alexia, inability to differentiate left and right side, acalculia, limb apraxia, apperceptive prosopagnosia, agraphia, homonymous visual field defects, and finger agnosia. At least three of these cognitive features need to be present early in the disease. The following should remain relatively unaffected: short-term memory, speech, non-visual language functions, executive functions, personality, and behavior.
Brain imaging tests (such as MRI, FDG-PET, SPECT) often reveal abnormal levels of activity or damage in the parts of the brain called occipitoparietal or occipitotemporal. However, it’s crucial to rule out other potential causes of cognitive impairment like renal failure or structural brain lesions such as tumors or vascular lesions, along with afferent visual pathology involving structures like optic nerve, optic chiasm, or optic tract.
Doctors keep in mind this condition among patients who present:
- Spatial disorientation
- Problems with color perception charts, despite having normal color vision
- Defects in visual fields (homonymous)
- Omission of letters on the vision chart
Testing for Posterior Cortical Atrophy
Before we can fully understand how the brain works, we have to find out what’s going wrong when illness arises. To do this, we do a range of tests, from eye tests to looking for physical changes in the brain.
In an eye test, we might find that the person has normal vision or that there are problems. These issues could involve loss of vision in one half of the visual field or irregular vision loss that we can’t easily explain using existing knowledge of brain injury or disease.
Next, we do a neuropsychological test, which is essentially a problem-solving quiz. During this test, the person is generally able to tell us where they are and remember things. They may, however, struggle with tasks involving math, spelling, or copying images, which are things our brains manage with some help from the parietal lobe, a part of the brain at the top and towards the back of the head. For instance, if a person finds it hard to count dots or draw a clock, this might suggest something is amiss in this brain region.
We also use brain scans to see any structure changes in the brain and see how the brain is functioning. We look for a protein called amyloid that can build up in the brain and harm its cells. In some diseases, this spread can mirror that of Alzheimer’s disease.
We can also do a PET scan, which provides a colorful map of your brain at work, showing which parts are using more energy. Sometimes though, even if the scan shows that the back part of the brain – the parietal and occipital lobes – isn’t working as it should, the brain doesn’t appear to have physically shrunk in this region. This is why it’s crucial to take the patient’s symptoms into account when making a diagnosis.
The MRI is another tool we use to look at how the brain is working by highlighting areas brain that is paler (we say “hypoperfused”) than the others, indicating reduced blood flow.
Genetic testing, or looking for certain genes that are passed down through families and can cause illnesses, is usually not necessary for some diseases.
The cerebrospinal fluid (CSF) testing is yet another evaluation method. This liquid surrounds our brain and spine and can show changes in diseases. In some instances, there might be less of a protein called amyloid-beta and more of two proteins known as tau and phosphorylated tau, suggesting the disease affects the brain similarly to Alzheimer’s. However, the increase in the tau proteins may not be as significant, meaning that these proteins’ ratios to amyloid-beta could be lower than in Alzheimer’s.
Recent advances in imaging techniques include a tau-PET scan, which is more specific in capturing images of tau proteins in the brain. In addition, the visual evoked potential (VEP) test, a test to see how the person’s brain responds to visual stimuli, could also be beneficial for the diagnosis.
Finally, a multiple-step evaluation for the doctor includes determining whether a posterior brain disease like PCA or other disorders like Alzheimer’s disease is the diagnosis by looking for particular biomarkers or substances that can indicate these diseases.
Treatment Options for Posterior Cortical Atrophy
While we don’t have a lot of information about the use of certain medications known as anticholinesterase inhibitors in patients with Posterior Cortical Atrophy (PCA), they might be beneficial for treating PCA because it often results from an underlying condition called Alzheimer’s disease. These drugs, along with another one called memantine, target the root cause of the symptoms. There have been some reports of PCA patients responding positively to anticholinesterase inhibitors.
As PCA progresses, it often leads to problems with vision while the patient’s awareness remains unaffected. This situation can cause a lot of stress, anxiety, and depression for the patient. That’s why it could be helpful to use medications known as selective serotonin reuptake inhibitors (SSRIs), which are commonly used to treat anxiety and mood changes.
Beyond medication, there are lots of ways to support PCA patients. These methods aim to help them function better each day, improve their daily skills, take care of themselves, and enhance their overall quality of life. Medical professionals often recommend strategies to help patients cope, psychological support, and specialized care.
Getting an early diagnosis is very important because it means patients can start implementing safety measures earlier on. For example, they might need to stop driving or change their home environment by removing any potentially hazardous furniture and making safety adjustments.
To make up for reading difficulties as the disease progresses, patients might find it helpful to engage with audiobooks. Technologies such as voice recognition and smartphone apps, as well as labels on doorknobs and pathways, can be useful for handling visual and spatial challenges. Adapting the home environment, especially the kitchen, bathroom, and stairs, can also improve their ability to manage daily life.
Finally, connecting patients and their families with support groups specifically for PCA can provide significant benefits. It’s critical for them to know they’re not alone, and they can find tremendous comfort and advice from those who understand what they’re going through.
What else can Posterior Cortical Atrophy be?
When diagnosing posterior cortical atrophy, it’s crucial to distinguish it from similar conditions such as typical Alzheimer’s disease. Patients with posterior cortical atrophy are usually younger and typically struggle with visual-spatial tasks, reading, and writing, while their memory remains relatively intact.
It’s also important not to confuse this condition with other diseases like Lewy body disease, corticobasal syndrome, and Creutzfeldt-Jakob disease (CJD). Lewy body disease symptoms might include sleep disorders, fluctuating mental status, visual hallucinations, parkinsonism, and sensitivity to certain antipsychotic drugs. For corticobasal syndrome, possible indicators could include uneven parkinsonism, muscle jerks or stiffness, sensory loss, motor apraxia, difficulty opening the eyelids, and feeling like a limb doesn’t belong to the body.
Diagnosing Creutzfeldt-Jakob disease (Heidenhain variant) can be especially challenging due to its variety of symptoms. It’s a fast-progressing disease leading to death usually within a year. Symptoms might include visual impairment due to the impact on the visual cortex, issues with visual control and perception (Balint syndrome), or challenges with writing, calculating, recognizing fingers, and orienting left-and-right (Gerstmann syndrome). The disease might also cause unsteadiness, muscle jerks, and unusual sensory experiences. MRI often shows a “cortical ribbon sign” in the parieto-occipital region.
Key differences from other similar conditions include:
- PCA often results in greater atrophy in the visual association cortex, unlike the hippocampal atrophy observed in Alzheimer’s disease. Patients with PCA also often have a clear understanding of their symptoms.
- Lewy body dementia often shows visual hallucinations and parkinsonian features, with scans showing extensions into the orbitofrontal and temporal cortex.
- The Heidenhain variant of Creutzfeldt-Jakob disease typically progresses quickly and presents with Anton’s syndrome, where certain brain damage patients are unaware of their loss of vision. It also tests positive for the 14-3-3 protein in cerebrospinal fluid analysis.
- Indicators of Corticobasal degeneration could include asymmetrical parkinsonism, difficulty opening the eyelids, and the sensation of an alien limb.
What to expect with Posterior Cortical Atrophy
People with posterior cortical atrophy experience a gradual decline in abilities like understanding how objects are positioned in space and how they see and perceive things. Essentially, their cognitive skills deteriorate to a point that they become functionally blind. This can cause them a lot of distress, especially if they are aware of these changes and the increasing need for help with self-care and daily activities.
This condition can also lead to extreme sadness and feelings of loss of control. Over time, as these cognitive skills decline further, posterior cortical atrophy becomes indistinguishable from advanced stages of a typical Alzheimer’s disease.
Possible Complications When Diagnosed with Posterior Cortical Atrophy
It’s crucial to quickly identify any problems and diagnose them to prevent issues such as falls or driving accidents. By making some adjustments to your home and making sure there is enough supervision available in challenging situations, you can avoid major problems related to the difficulties with understanding and relating to space which typically arises from visual-spatial impairments.
To ensure a safe environment:
- Early identification and diagnosis of problems
- Preventing falls and avoiding driving accidents
- Making necessary changes to the home
- Ensuring adequate supervision in challenging situations
Preventing Posterior Cortical Atrophy
It’s very important that patients and their families understand their diagnosis and how it may affect their daily life. In particular, it might help the patient to declutter their living space, use clues that don’t rely on vision, and arrange for round-the-clock supervision if needed. Assistance with tasks that may be risky or difficult, such as cooking, can be beneficial. Therapists who specialize in these areas can evaluate things like a patient’s ability to drive safely.
Occupational therapists, who help patients to improve their skills needed for daily tasks, can also be really helpful. They can provide ways to adapt to any abilities the patient may have lost, tailored to their specific situation.
