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CBD


  


 Introduction  

Corticobasal degeneration (CBD) is a rare condition where brain cells become damaged over time and certain sections of the brain start to shrink.

CBD is a progressive condition. This means that the initial symptoms will become more severe over time and new symptoms may also develop.

Initial symptoms of CBD include:



sudden problems controlling certain limbs



loss of balance and co-ordination



slowness and reduced mobility



As CBD progresses, the symptoms will become more wide-ranging and troublesome. They will include:



muscle spasms and stiffness



an ongoing decline of mental functions (dementia)



difficulty swallowing food and liquid (dysphagia)



difficulty speaking



 

 What causes CBD? 

The brain damage associated with CBD is caused by a build-up of a protein in the brain called tau. Tau is usually found in low levels in the brain, but in CBD it forms clumps that kill nearby brain cells.

This damages vital parts of the brain, such as the cortex and basal ganglia, which are responsible for important functions, including:



movement



speech



higher thought processes, such as planning and understanding



Exactly why tau protein builds up and forms clumps isn't known.

 

 Diagnosing CBD 

There's no single test for diagnosing CBD. Instead, a diagnosis will be made based on the type and pattern of symptoms and by ruling out other conditions that can cause similar symptoms, such as a stroke, Parkinson’s disease, motor neurone disease and more common types of dementia.

As CBD shares symptoms with a number of other more common conditions, confirming the diagnosis can be challenging and may take several months, or in some cases years.

 

 Treating CBD 

There's no cure for CBD. Several medications, such as memantine, have been suggested to slow down the condition's progression and improve the function of the brain, but it's not clear how effective they are.

Most treatments for CBD focus on relieving a person's symptoms and helping them cope with daily life. These include medication to relax muscles and using feeding tubes to overcome swallowing problems.

 

 Complications of CBD 

CBD isn’t itself life-threatening, but can lead to serious complications.

Difficulty swallowing (dysphagia) is a common symptom of CBD, which increases the risk of a person choking or inhaling food or liquid into their airway (aspiration).

If this happens, aspiration pneumonia can develop. This is a lung infection that's triggered when a small piece of food enters the lungs.

 


 



 Who is affected by CBD? 

An estimated six people in every 100,000 are affected by CBD.

However, it may affect many more people than those diagnosed with the condition because CBD may be misdiagnosed as a stroke, progressive supranuclear palsy (PSP) or another condition with similar symptoms, such as Alzheimer's disease.

If someone develops CBD, CBD symptoms will usually start at 50-80 years of age. The condition may be more common in women but because it's so rare, it's difficult to be certain.

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 Symptoms of corticobasal degeneration  

Corticobasal degeneration (CBD) is a progressive condition. This means the symptoms develop gradually and become more severe over the course of many years.

It's important to realise that only a few people will experience all the symptoms described below. The symptoms will also vary in severity from person to person.

Initial symptoms

One of the typical signs of CBD is difficulty controlling one of your limbs. In most people, it's usually the hand or arm that's affected, but sometimes it can be the leg.

You may have muscle stiffness, rigidity and spasms in your limb, and you may find it increasingly difficult to use the affected limb. Some people with CBD have reported that it feels like the affected limb is no longer under their control and doesn't belong to them. This is known as alien limb syndrome.

Another common initial symptom of CBD is that you begin to lose your sense of balance and co-ordination, which leads to walking difficulties.

Later symptoms

As CBD progresses, it will affect other limbs, usually both your arms and legs.

Your balance and co-ordination will get worse and it's likely you'll find it increasingly difficult to walk. Most people have problems with their speech, which will become slow and slurred, making it difficult to understand.

Eye muscles are usually also affected. Many people have problems moving their eyes up and down and sometimes to the left and right. This can increase the risks of falls and cause problems carrying out everyday tasks, such as eating and reading.

At this stage, many people with CBD start to experience symptoms of dementia, including:



problems recalling words and expressing yourself using the correct language



short-term memory loss and increasing forgetfulness



problems carrying out tasks that require planning



problems coping with sudden and unexpected situations, such as suddenly realising you've forgotten the keys to your house



It's also common for someone with CBD to experience personality changes and become depressed, apathetic, irritable, agitated or anxious.

A small number of people with CBD also develop obsessive compulsive disorder (OCD).

 

 Advanced stages 

As CBD reaches an advanced stage, the symptoms of muscle stiffness and rigidity will continue to get worse, and you may lose the ability to move one or more of your limbs. Some people with advanced CBD are unable to walk and need a wheelchair.

It's also likely that your speech will continue to deteriorate and people may find it difficult to understand you.

Problems controlling your eye muscles are also likely to get worse. Some people with advanced CBD will not be able to change the direction of their gaze and will only be able to stare straight ahead.

For a small number of people with advanced CBD, dementia will worsen and they'll need constant care.

Most people with advanced CBD will find it increasingly difficult to swallow food and liquid. This is known as dysphagia. At some point, people with CBD will need to consider the possible benefits and drawbacks of using a feeding tube.

As a result of dysphagia, many people with CBD will experience repeated chest infections caused by fluid or small food particles falling down into their lungs. This can lead to a serious condition called aspiration pneumonia, which is the leading cause of death in cases of CBD.

 

 Causes of corticobasal degeneration  

Corticobasal degeneration (CBD) is caused by a progressive loss of brain cells.

It’s one of a group of conditions called '4 repeat tauopathies', characterised by an excess amount of an abnormal protein called tau protein.

In a healthy brain, tau protein is found in low levels, but in CBD the levels increase, forming clumps that are thought to kill nearby brain cells.

This shrinks parts of the brain responsible for movement, speech and higher thought processes, such as planning and understanding.

The symptoms of CBD are similar to those of another condition called progressive supranuclear palsy (PSP). However, in PSP the pattern of brain damage is slightly different. It's possible that both CBD and PSP are two related syndromes that have the same underlying causes.

It's not known what leads to the over-production of the tau protein and the resulting death of brain cells.

 

 Genetic link  

One theory is that CBD could be the result of a mutation in the gene responsible for producing the tau protein. This is known as the MAPT gene (microtubule-associated protein tau gene).

A genetic mutation occurs when the instructions found in all living cells become scrambled in some way. This leads to one or more of the body's processes not working as it should.

There's evidence that the genetic mutations affecting the MAPT gene are responsible for conditions with similar symptoms, such as some types of dementia and PSP.

However, there's still no firm evidence to support the theory that mutations in the MAPT gene are responsible for CBD.

Also, as CBD doesn't run in families, it would appear that the condition isn't wholly caused by the genes a person inherits from their parents.

One or more environmental factors may trigger CBD in people who are susceptible to it.

Possible factors could include:



a virus or other type of infectious agent, which may slowly infect the brain over many years



an unidentified neurotoxin (poison that damages the brain and nerve cells) that may be present in the environment



 

 Care and support 

If you or someone you know develops CBD, you may need information and advice about caring for them.

See the Care and Support section for information about all aspects of caring for others, as well as advice for carers themselves.

Causes of corticobasal degeneration 

Corticobasal degeneration (CBD) is caused by a progressive loss of brain cells.

It’s one of a group of conditions called '4 repeat tauopathies', characterised by an excess amount of an abnormal protein called tau protein.

In a healthy brain, tau protein is found in low levels, but in CBD the levels increase, forming clumps that are thought to kill nearby brain cells.

This shrinks parts of the brain responsible for movement, speech and higher thought processes, such as planning and understanding.

The symptoms of CBD are similar to those of another condition called progressive supranuclear palsy (PSP). However, in PSP the pattern of brain damage is slightly different. It's possible that both CBD and PSP are two related syndromes that have the same underlying causes.

It's not known what leads to the over-production of the tau protein and the resulting death of brain cells.

 

 Genetic link  

One theory is that CBD could be the result of a mutation in the gene responsible for producing the tau protein. This is known as the MAPT gene (microtubule-associated protein tau gene).

A genetic mutation occurs when the instructions found in all living cells become scrambled in some way. This leads to one or more of the body's processes not working as it should.

There's evidence that the genetic mutations affecting the MAPT gene are responsible for conditions with similar symptoms, such as some types of dementia and PSP.

However, there's still no firm evidence to support the theory that mutations in the MAPT gene are responsible for CBD.

Also, as CBD doesn't run in families, it would appear that the condition isn't wholly caused by the genes a person inherits from their parents.

One or more environmental factors may trigger CBD in people who are susceptible to it.

Possible factors could include:



a virus or other type of infectious agent, which may slowly infect the brain over many years



an unidentified neurotoxin (poison that damages the brain and nerve cells) that may be present in the environment



 

 

 Care and support 

If you or someone you know develops CBD, you may need information and advice about caring for them.

See the Care and Support section for information about all aspects of caring for others, as well as advice for carers themselves.

 

 Diagnosing corticobasal degeneration  

There's no single test to help diagnose corticobasal degeneration (CBD).

Instead, the diagnosis is based on the type and pattern of symptoms and ruling out other conditions that can cause similar symptoms, such as a stroke, Parkinson’s disease, motor neurone disease and more common types of dementia.

As CBD shares symptoms with many other more common conditions, confirming the diagnosis can be challenging and may take several months, or in some cases years.

 

 Imaging scans 

If you have symptoms that suggest there's something wrong with your brain, it's likely you'll be referred for brain imaging studies.

These may include a:



magnetic resonance imaging (MRI) scan – where strong magnetic fields are used to produce a detailed image of the inside of the brain



DatSCAN – a test that involves using a small amount of radioactivity to obtain images of an area of your brain; it can help differentiate between brain disorders



positive emission tomography (PET) scan – similar to an MRI scan, a PET scan has the added advantage that it can assess how different parts of the brain are functioning



These types of imaging studies can be useful in ruling out other possible causes of CBD, such as a brain tumour or stroke.

They can also detect abnormal changes to the brain that are consistent with a diagnosis of CBD, such as shrinkage in the cortex and basal ganglia.

Ruling out Parkinson’s disease

You may also be prescribed a medication called levodopa. This can help determine whether your symptoms are caused by CBD or Parkinson’s disease.

This is because people with Parkinson’s disease usually experience a marked improvement in their symptoms after taking levodopa. However, this isn't the case for people with CBD, and levodopa usually only has a limited effect in improving symptoms.

 

 Neuropsychological testing 

It's also likely you'll be referred to a neurologist (a nerve and brain specialist) and you may need to have neuropsychological testing.

This involves having a series of tests to evaluate the full extent of your symptoms and their impact on your mental abilities. The tests will look at abilities such as:



memory



concentration



understanding language



processing visual information, such as words and pictures



Most people with CBD have a distinct pattern in terms of their mental abilities. They often have what's known as subcortical dementia which affects their planning abilities.

They have poor concentration, a low attention span and problems with spoken language and processing visual information.

Their memory of previously learned facts, such as who was the last prime minister, is usually unaffected.

 

 Receiving the diagnosis 

Once all other possible causes of your symptoms have been ruled out, a confident diagnosis of CBD can usually be made.

Being told that you have CBD can be an emotionally devastating experience, and the news can often be difficult to take in. Therefore, at this time, it's important that you have the support of your family and care team, who will be able to help you come to terms with the diagnosis.

A charity called the PSP Association provides help and support for people with CBD. The charity mainly helps people with progressive supranuclear palsy (PSP), but as the symptoms and treatments of CBD and PSP are similar, the PSP Association also supports people with CBD.

As your symptoms progress, you'll need full-time care and you may also need assistant technology, such as a wheelchair, to help with activities.

 





 Speech and language therapy

 

 

A speech and language therapist explains how the therapy works and who can benefit from it.

 


Media last reviewed: 11/07/2013

Next review due: 11/07/2015

 






Care and support

If you or someone you know develops CBD, you may need information and advice about caring for people with a long-term condition.

The Care and support section on NHS Choices provides a wide range of useful information about all aspects of caring for others, as well as advice for carers themselves.



End of life care guide

Complications of corticobasal degeneration 

Aspiration pneumonia is a potentially serious complication of corticobasal degeneration (CBD).

Aspiration pneumonia is a lung infection that's triggered when a small piece of food enters the lungs.

People with CBD are particularly vulnerable to aspiration pneumonia because their impaired swallowing reflexes mean that their larynx (voice box) doesn't close when they swallow. This leaves their lungs unprotected.

The symptoms of aspiration pneumonia include:



high temperature (fever) of 38C or above



fatigue (extreme tiredness)



chest pain



shortness of breath



blue skin (cyanosis) due to a lack of oxygen



wheezing



You may also have a cough that sometimes produces foul-smelling phlegm and may contain traces of blood and pus.

Contact your care team immediately if you're being treated for CBD and you develop these symptoms.

The symptoms of aspiration pneumonia can range from mild to severe. In severe cases, admission to hospital will be needed so that intravenous antibiotics can be given.

In particularly vulnerable or frail people, there's a chance that the infection could cause their lungs to become filled with fluid, preventing them from working properly. This is known as acute respiratory distress syndrome (ARDS). 

As most people with advanced CBD are vulnerable and frail, repeated episodes of aspiration pneumonia often result in ARDS and then death.