Corticobasal degeneration (CBD) is a rare and progressive condition where increasing numbers of brain cells are damaged over time, and certain sections of the brain begin to shrink (neurodegeneration).
Symptoms of CBD include:
- stiffness, jerkiness, and clumsiness in one or more limbs
- mild to moderate dementia (a decline in mental abilities, such as memory, thinking, and understanding)
- increasing difficulties with speaking and swallowing
The cause of CBD is unknown.
How common is CBD?
CBD is a rare condition. In England, it is estimated that there is one new case diagnosed every year for every 100,000 people. However, this figure may underestimate the true number of those affected by CBD because many cases may have been misdiagnosed, often as stroke, or progressive supranuclear palsy (PSP). PSP is a slightly more common neurodegenerative condition, which shares many of the symptoms of CBD.
Most cases of CBD affect people who are 60-80 years of age, with 67 being the average age for the onset of symptoms. CBD may be more common in women than in men, but because the condition is so rare, it is difficult to be entirely certain.
CBD is a progressive condition, which means that the initial symptoms will become more severe over time, and that new symptoms may develop. The rate at which symptoms progress can vary widely between individuals, but people typically live for around eight years after the onset of symptoms.
People with CBD are very vulnerable to developing other complications, such as pneumonia, which can be fatal.
Research into treatments for CBD is ongoing, but there are no current treatments that can be used to cure the condition. Therefore, treatment for CBD focuses on relieving the symptoms, and ensuring that the person with the condition has the best possible quality of life.
Symptoms of corticobasal degeneration
Corticobasal degeneration (CBD) is a progressive condition, which means that the symptoms develop gradually, before becoming more severe over the space of many years.
However, it is important to realise that only a few people will experience all of the symptoms that are outlined below. Also, individual symptoms can vary in severity from person to person.
The most common initial symptom of CBD is a sudden difficulty in controlling one of your limbs. In most people, this is usually their hand or arm, but sometimes a person's leg can be affected.
You may experience muscle stiffness, rigidity, and spasms, in your limb, and you will probably 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 does not 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.
As CBD progresses, the problems that you have controlling your limb, and the symptoms of muscle spasms and stiffness, will spread to other limbs, usually in both your arms and legs.
Balance and co-ordination problems will become more pronounced, and many people find it increasingly difficult to walk. Most people will begin to experience problems with their speech, as it becomes slow and slurred, making it difficult to understand.
At this stage, the muscles of the eyes are usually also affected, with many people having problems moving their eyes up and down and, less commonly, to the left and right. This can increase the risks of falls, as well as contributing to problems with eating and carrying out everyday tasks.
At the intermediate stage of the condition, many people with CBD will begin to experience symptoms of mild to moderate dementia. This can take the form of:
- problems recalling words and expressing yourself by using the correct language
- short-term memory loss and increasing forgetfulness
- problems performing tasks that require forward planning
- problems coping with sudden and unexpected situations, such as suddenly realising that you have forgotten the keys to your house
It is also common for someone with CBD to experience personality changes and related mental health conditions including:
A significant minority of people with CBD also develop obsessive compulsive disorder (OCD).
This usually takes the form of repetitive actions, such as repeatedly picking up and then putting down an object, an obsessive desire for cleanliness, and repeated 'checking activities', such as checking all the windows are locked or the cooker has been turned off.
During the advanced stages of CBD, 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 require a wheelchair.
The quality of your speech will probably continue to deteriorate and it may become almost unintelligible to others.
Problems controlling your eye muscles are also likely to get worse, and some people with advanced CBD will be unable 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, their dementia will worsen and they will require constant care.
Most people with advanced CBD will find it increasingly difficult to swallow food and liquid. This is known as dysphagia. At some time, 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 that are caused by fluids or small particles of food that inadvertently fall 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
Cortiocobasal degeneration (CBD) is caused by a progressive loss of brain cells, and the shrinkage (atrophy) of parts of the brain that are responsible for movement, speech, and the higher thought processes, such as understanding and planning.
It is thought that the damage and shrinkage to the brain is caused by an the over-production of a protein called tau, which naturally occurs in the brain, but at a lot lower level than seen in cases of CBD. In cases of CBD, the excess levels of tau forms into clumps which are thought to kill nearby brain cells.
CBD has similar symptoms to another neurodegenerative condition called progressive supranuclear palsy (PSP). However, in PSP the pattern of brain damage is slightly different, so it may be the case that both CBD and PSP are two related syndromes that are caused by the same underlying cause (or causes).
It is not known what leads to the over-production of the tau protein and the resulting death of brain cells. Recent research indicates that genetic factors make a person more likely to develop CBD. However, there is no evidence to suggest that CBD can be passed down from a parent to their child, and most experts think that it is unlikely that CBD is an inherited condition.
Further research is ongoing to identify what other factors may trigger CBD. Two environmental triggers that have been suggested include:
- an as yet, unidentified virus, or other type of infectious agent, which may slowly infect the brain over many years
an unidentified neurotoxin (a poison that damages the brain and nerve cells) that may be present in the environment
Diagnosing corticobasal degeneration
There is no single test that can be used to diagnose cortiocobasal degeneration (CBD). Instead, the diagnosis is based on the type and pattern of symptoms, while ruling out other conditions that can cause similar symptoms, such as stroke, Parkinson's disease, motor neurone disease, and more common types of dementia.
In order to rule out these, other conditions, it is likely that you will be referred for a series of imaging scans to check whether there are any underlying problems with your brain, such as a brain tumour, or dementia, that could help explain your symptoms. Imaging scans may also be able to detect whether certain areas of the brain have experienced shrinkage.
You may also be prescribed a medication called levodopa, which 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 is not the case for people with CBD, and levodopa usually only has a limited effect in improving symptoms
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 is important that you have the support of your family and care team who will be able to help you to 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.
Treatment of corticobasal degeneration
As cortiocobasal degeneration (CBD) can have an impact on many different aspects of your life and health, the treatment of CBD is provided by a team of health and social care professionals working together. This type of team is known as a multidisciplinary team (MDT) because it contains experts from many different healthcare disciplines. See box, left.
While there are no medications that can be used to directly treat CBD, there are some medications that can be used help control some of the condition's symptoms. These are discussed below.
Levodopa is a medication that is often used to treat Parkinson's disease. While it is usually less effective for people with CBD, for some people it may provide moderate, short-term improvement in muscle stiffness and rigidity.
Levodopa works by increasing the levels of a brain chemical called dopamine by transmitting messages from your brain that control and coordinate your body's movements. Therefore, an increase in dopamine levels may lead to a corresponding improvement in muscle control.
Common side effects of levodopa are:
However, these side effects usually pass within a few weeks, once your body becomes use to the medication. Other side effects can occur if you take levodopa on a long-term basis and include:
- involuntary, physical movements, such as jerking
- mood changes - for example, feeling more anxious
Baclofen is a type of medication that can be used to treat muscle stiffness and rigidity. It works by blocking some of the nerve signals that cause muscle stiffness.
Side effects of baclofen may include:
- an increased need to urinate
These side effects usually pass once your body becomes use to the medication.
Clonazepam is a type of medication that can be used to treat symptoms of muscle spasms.
Side effects of clonazepam may include:
- muscle weakness
- loss of co-ordination
As with baclofen, the side effects of clonazepam usually pass once your body has become used to the medication.
You should avoid drinking alcohol while you are taking clonzepam because it can make the side effects listed above worse, as well as magnifying the effects of the alcohol.
A physiotherapist can provide you with advice about how to make the most of your remaining mobility by using exercise. Regular exercise can help to strengthen your muscles, improve your posture and prevent stiffening of your joints.
Your physiotherapist will also be able to provide advice about any aids that could be of benefit to you, such as a walking frame, or shoes that have been specially designed to reduce your risk of slipping and falling.
Cognitive stimulation is a type of therapy that is used to treat the symptoms of dementia. It involves taking part in activities and exercises that are designed to improve your memory, problem-solving skills, and language ability.
Cognitive stimulation is provided by a trained carer and usually consists of two 45-minute sessions a week. During these sessions, you will be involved in discussions about a variety of topics, as well as taking part in word and memory games, and other activities, such as identifying pictures of famous people.
Speech and language therapist (SLT)
A speech and language therapist (SLT) can help to improve your speech and swallowing problems. They can also teach you a number of techniques to make the most of your speech function by making your voice as clear as possible.
As CBD progresses, you may need some sort of assistive technology to help you to communicate. A range of communication aids are available, and your SLT will be able to advise you about the devices that will be most suitable for you.
Your SLT may also be able to teach you exercises to help stimulate the nerves that are used to trigger your swallowing reflex and strengthen the muscles that are used during swallowing.
There are also a number of physical techniques that can be used to make swallowing easier. For example, some people find that moving their chin forward while swallowing helps to prevent any food from entering their airways.
As the symptoms of your dysphagia become more severe, you will require additional treatment to compensate for your swallowing difficulties.
You may be referred to a dietitian, who will advise you about making changes to your diet, such as incorporating food and liquids that are easier to swallow while ensuring that you receive a healthy, balanced diet.
For example, mashed potatoes are a good source of carbohydrates, while scrambled eggs and cheese are high in protein and calcium.
Feeding tubes may be recommended in severe cases of dysphagia that increase your risk of developing malnutrition and dehydration. You should discuss the pros and cons of feeding tubes with your family and care team, preferably when your symptoms of dysphagia are at an early stage.
There are two types of feeding tubes:
- nasogastric tube - a tube that is passed down your nose and into your stomach
- percutaneous endoscopic gastrostomy (PEG) tube - a tube that is surgically implanted directly into your stomach, which passes through a small incision on the surface of your stomach or abdomen
Nasogastric tubes are designed for short-term use and last for 10-28 days before they need to be replaced. PEG tubes are designed for long-term use and last for up to six months before they need to be replaced.
An occupational therapist (OT) can provide advice about the best ways of increasing your safety and preventing trips and falls during your day-to-day activities.
For example, many people with CBD benefit from having bars placed along the sides of their bath to make it easier to get in and out.
The OT will also be able to spot potential hazards in your home that could lead to a fall, such as poor lighting, badly secured rugs and crowded walkways and corridors.
Many people with CBD draw up an advanced directive. An advanced directive is where you make your treatment preferences known in advance in case you cannot communicate your decisions later because you are too ill.
Issues that can be covered by an advanced directive include:
- whether you want to be treated at home, in a hospice, or in a hospital, once you reach the final stages of CBD
- what type of painkillers you would be willing to take
- whether you would be willing to use a feeding tube if you were no longer able to swallow food and liquid
- whether you are willing to donate any of your organs once you die (the brains of people with CBD are particularly useful for ongoing research)
- if you experience respiratory failure (loss of lung function) due to aspiration pnuemonia, whether you would be willing to be resuscitated by artificial means, such as having a breathing tube inserted into your neck
You cannot request anything illegal in your advanced directive.
Your care team will be able to provide you with more information and advice about advanced directives.
Complications of corticobasal degeneration
One of the most potentially serious complications of corticobasal degeneration (CBD) is aspiration pneumonia.
Aspiration pneumonia is a lung infection that is 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) does not close during swallowing, so their lungs are not protected.
The symptoms of aspiration pneumonia include:
- high temperature (fever) of or above 38ºC
- chest pain,
- shortness of breath,
- blue skin (cyanosis), due to a lack of oxygen, and
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 are being treated for PSP and you develop these symptoms. If this is not possible, contact your local out-of-hours service, or call NHS Direct on 0845 4647.
The symptoms of aspiration pneumonia can range from mild to severe. Severe cases will require admission to hospital and treatment with intravenous antibiotics.
In particularly vulnerable or frail people there is a chance that the infection could lead to their lungs becoming filled with fluid, preventing them from working properly. This is known as acute respiratory distress syndrome (ARDS).
Unfortunately, as most people with advanced CBD are vulnerable and frail, repeated episodes of aspiration pneumonia often result in ARDS and then death.