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What is posterior cortical atrophy
(PCA)?
Posterior cortical atrophy (PCA), also known as Benson's syndrome, is a
progressive degenerative condition where damage to brain cells is particularly
focused at the back (posterior) of the brain, the region responsible for visual
processing. This damage to brain cells leads to cell death and loss of volume
or 'atrophy' of the posterior cortical regions - hence the name. In the vast
majority of cases the underlying cause is Alzheimer's disease.
The death of brain cells is accompanied by accumulation of toxic proteins,
amyloid and tau, that form plaques and tangles in the same way as is seen in
typical Alzheimer's disease. PCA may therefore be referred to as an atypical
variant of Alzheimer's disease.
Although PCA is caused by Alzheimer's disease, it can also be due to other
diseases including dementia with Lewy bodies and Creutzfeld Jacob disease.
PCA is a rare condition, thought to affect less than five per cent of people with
Alzheimer's disease, although epidemiological studies are lacking and PCA
has been under-recognised in the past.
How is PCA different from typical Alzheimer's
disease?
Despite usually being caused by the same disease process, the effects of PCA
and typical Alzheimer's disease upon the behaviour, thought processes and
skills of individuals with each condition are very different.
Typical Alzheimer's disease is most commonly associated with deterioration in
memory, followed by gradual progressive decline in other cognitive functions
including language, calculation, planning, and perceptual skills. By contrast,
individuals with PCA tend initially to have well-preserved memory but instead
show a decline in vision, and experience difficulties with performing skilled
movements and with literacy skills.
These functions are controlled by the back region of the brain and the
relatively selective loss of visual abilities, compared to the more general
decline seen in typical Alzheimer's disease, occurs because initial damage to
brain cells is focused in this region. As the disease progresses, this damage
may spread to other parts of the brain causing people with later-stage PCA to
show more general symptoms of dementia including memory problems.
Symptoms
The most common problem first noticed by individuals with PCA is with vision.
People with PCA may often go to see an optician at first, thinking that their
difficulties are due to a problem with their eyes and that they may need new
glasses. Visual impairment commonly develops as people get older, and in
most cases a decline in vision is due to this natural ageing process.
However, in people with PCA, visual problems are not due to problems with
their eyes. Rather, the affected brain cannot interpret and process the
information received from the person's eyes, which are still healthy. The visual
problems experienced may vary widely but often include some or all of the
following:
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• Difficulty recognising objects in pictures (for example household items in a
catalogue, especially if the pictures were taken from obscure angles or the
picture is incomplete).
• Difficulty recognising faces (for example TV characters, friends, relatives).
• Decline in spatial awareness, for example in judging distances and speeds.
This might result in the person missing when reaching out to pick something
up, finding it hard to press the correct numbers on a telephone,
experiencing difficulties with driving or descending stairs, and in judging the
speed of moving traffic. Stationary objects may also appear to move.
• Difficulty moving from the end of one line to the beginning of the next when
reading.
• When reading, particular words or letters appear to move around or become
superimposed over one another.
• Difficulty in reading certain types of text (for example large print such as
newspaper headlines, handwritten notes).
• Perceiving objects as having an unusual colour.
• Experiencing increased sensitivity to bright light or shiny surfaces.
• Experiencing double vision or feeling that their eyes are jerking around or
not completely under their control.
• Particular difficulty seeing clearly in fading or low light conditions.
Some problems may be particularly hard to understand - for instance small
print may be easier to read than large print - or objects that are 'just under
someone's nose' are not recognised and then suddenly 'seen'. These
problems, especially if not clearly explained, may be a particular cause of
frustration for those around the individual with PCA as well as for the individual
themselves.
However, vision is not the primary or only area of difficulty for everyone with
PCA. Skills such as literacy, numeracy, and the ability to make skilled
movements may also be affected. Such difficulties may be experienced in the
following ways:
• Difficulties with handwriting, such as with spelling or remembering the shape
or name of particular letters or numbers.
• Slowness and difficulty with mental arithmetic.
• Problems dealing with money and small change.
• Difficulties with co-ordination, leading to awkwardness making gestures (eg
waving, thumbs up) and struggling to use particular tools (eg cutlery,
scissors, glasses).
• Problems with dressing and clothing (partly related to difficulties with visual
perception).
• Problems with sitting down on a chair, or trying to sit on the wrong seat in a
car.
PCA can affect people in different ways initially. In some instances, the
disease affects both sides of the brain equally, leading to a combination of
many of the symptoms described above. For other people, the disease affects
one particular brain area earlier or more significantly. For example, problems
with spelling and writing might be the first sign of the condition while vision is
relatively unaffected.
Getting a diagnosis
PCA tends to affect people at an earlier age than typical Alzheimer's disease,
with individuals often being in their mid-fifties or early sixties when they
experience the initial symptoms. However, it can also affect older people. The
first signs are often subtle symptoms which may be difficult for the person to
explain. Individuals with early visual complaints are typically referred to
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opticians and eye specialists before referral to a neurologist.
Even following an appropriate referral, it may take some time before a formal
diagnosis is made. Understandably, patients may feel frustrated by the time of
diagnosis, which can take up to three years after the onset of symptoms.
Tests
There is no diagnostic test for PCA. However, specialised visual tests
(organised by eye specialists), neuropsychological tests of cognitive skills (for
example memory, perception, literacy), blood tests, brain scans (magnetic
resonance imagery (MRI) or computerised tomography (CT)), lumbar puncture
(examination of the fluid circulating around the brain and spinal cord) and EEG
(recording of the electrical activities of the brain) may help to exclude
potentially treatable causes such as infection, inflammation or brain tumour.
Shrinkage of the back part of the brain as a result of brain cell loss may be
visible on the brain scan.
It may still be difficult to come up with one diagnosis in life. Often, definitive
diagnosis can only be made following post mortem examination of brain tissue
by a pathologist.
Later stages of the disease
As the disease progresses, word finding, day-to-day memory and general
cognitive functions may become affected, and people develop the symptoms
of typical Alzheimer's disease. In the later stages of the disease, people may
experience jerking movements of their limbs and even seizures.
Unfortunately, as with typical Alzheimer's disease, the condition is progressive
with a gradual deterioration of skills and abilities over the years following
diagnosis. The duration of the PCA condition is poorly understood. Some
people live approximately the same length of time as individuals with typical
Alzheimer's disease (on average 10-12 years following the onset of symptoms)
while others live with the condition for longer.
Treatment
In the majority of cases PCA is caused by Alzheimer's disease, for which there
are a range of drugs available. Donepezil (Aricept), rivastigmine (Exelon) and
galantamine (Reminyl) are cholinesterase inhibitors (see Factsheet 407, Drug
treatments for Alzheimer's disease). These drugs are designed to boost the
function of brain cells to compensate (partly) for damage caused by
Alzheimer's disease. All these drugs have shown benefit in individuals with
Alzheimer's disease in controlled clinical trials.
So far, no clinical trials have been completed to determine the efficacy of these
drugs specifically for treatment of PCA, although there is currently an ongoing
study at the Hospital for Neurology in London. Since the underlying cause of
Alzheimer's disease and PCA can be the same, it is thought that these
treatments have the same beneficial effect for people with PCA. It is important
to note, however, that these medications are only designed to treat the
symptoms of the disease and are not a cure.
Although individuals with PCA often show relatively preserved insight, they are
frequently very affected by the decline in their ability to interact successfully
with the visual world around them. Individuals struggle with a loss of
independence as their ability to perform the basic activities of daily living is
compromised and they can no longer enjoy their previous hobbies, especially
reading. This can lead to depression, irritability, frustration and a loss of
self-confidence. Individuals with PCA who are experiencing low mood may
therefore benefit from antidepressant medication.
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Supporting people with PCA
There are a number of support services that are offered to individuals with
typical Alzheimer's disease and other forms of dementia that benefit people
with PCA. These include the distribution of information about available financial
benefits (see Factsheet 413, Benefits and 431, Benefit rates and
income/savings thresholds) and financial provisions (see Factsheets 467,
Financial and legal affairs and 472, Enduring power of attorney and lasting
powers of attorney).
There is a range of practical visual aids designed to assist individuals with
different types of visual impairment which may be of use to people with PCA.
These include devices such as talking clocks and watches, mobile telephones
with simplified displays or pre-programmable direct-dial buttons, and cooking
aids such as sensors which beep when a cup is nearly full.
There is also an increasingly wide range of talking books and audio recordings
available on CD or online, ranging from romantic novels to biographies and
technical manuals. Audio guides are also available for many cultural events
including theatres and museums.
Some people with PCA adopt a range of strategies to help them deal with
difficulties, including asking people to introduce themselves at the beginning of
a conversation. Practical coping strategies also include using shoelaces that
stretch or buying shoes without shoelaces.
The National Hospital for Neurology and Neurosurgery run a regular PCA
support group offering information, advice and social opportunities for
individuals with PCA and their families. Patients with PCA not currently being
treated at the hospital will require a referral letter from their consulting doctor to
confirm their diagnosis and their suitability for joining the group.
Your local Alzheimer's Society branch will always be willing to talk to you and
offer advice and information to support your needs.
For more information, Dementia Catalogue, our specialist dementia information
resource is available on the website at alzheimers.org.uk/dementiacatalogue
Useful organisations
AbilityNet
PO Box 94Warwick CV34 5WST 0800 269 545 E enquiries@abilitynet.org.uk
W www.abilitynet.org.uk
Provides information on and tools for screen-reading, voice recognition and
information technology.
BBC Audio description
W www.bbc.co.uk/audiodescription
Offers a list of audio-described BBC programmes.
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In Touch
W www.bbc.co.uk/radio4/intouch
BBC Radio 4 programme with news, views and information for people who are
blind or partially-sighted. You can listen to the latest edition via the website.
PCA Support Group (National Hospital for Neurology and
Neurosurgery)
Dr Sebastian CrutchDementia Research CentreBox 16, National Hospital
Queen SquareLondon WC1N 3BGT 0845 155 5000 ext. 723113
Support group offering information, advice and social opportunities for
individuals with PCA and their families.
Royal National Institute for Blind People (RNIB)
105 Judd StreetLondon WC1H 9NET 020 7388 1266E resource@rnib.org.ukW
http://www.rnib.org.uk/
Charity offering information, support and advice to people with sight loss.
Factsheet 479
Last updated: February 2009Last reviewed: February 2009
Written by: Dr Sebastian Crutch, Dr Susie Henley and Dr Basil Ridha at the
National Hospital for Neurology and Neurosurgery, Queen Square, London
with the help of members of the National Hospital PCA Support Group and the
support of the Myrtle Ellis Fund.
Reviewed by: Prof Nick Fox, Professor of Neurology and MRC Senior Clinical
Fellow at the Institute of Neurology, University College London in the Dementia
Research Centre.
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