Corticobasal degeneration: symptoms, causes, treatment and life expectancy

The NHS says people with CBD develop a range of difficulties with movement, speech, memory and swallowing. The condition tends to develop gradually, which means it can be mistaken for another condition at first, such as Parkinson's disease, dementia or a stroke. The symptoms typically become more severe over several years, although the speed varies, and most people do not experience all of them.

Early on, one limb is usually affected, most often a hand or arm and sometimes a leg. The NHS lists a clumsy or "useless" hand, muscle stiffness, shaking and muscle spasms (dystonia), loss of feeling, and feeling that the limb does not belong to you (an "alien" limb). Some people also have problems with walking and co-ordination.

As CBD progresses it may affect other limbs, and walking, balance and co-ordination may get worse. Many people have slow and slurred speech. Some people have dementia, with problems recalling words, reading and using language, short-term memory loss, difficulty planning, difficulty with numbers and difficulty judging where things are. The NHS also lists personality changes such as becoming apathetic, irritable, agitated or anxious.

In advanced stages muscle stiffness continues to get worse and people may lose the ability to move one or more limbs, need a wheelchair or help to transfer, have worsening speech and dementia, uncontrollable blinking, and increasing swallowing difficulty that may mean a feeding tube is required. Swallowing problems can cause chest infections or aspiration pneumonia, which can be life-threatening.

The NHS says CBD is a rare condition in which brain cells become damaged or die over time. It is often also called corticobasal syndrome (CBS). The PSP Association explains that the two terms are related but not identical: CBD refers to the underlying brain disease, while CBS refers to the set of symptoms a person has, which usually affects one side of the body first.

The PSP Association says CBS can also be caused by other conditions affecting the same parts of the brain, such as Alzheimer's disease, progressive supranuclear palsy (PSP) and stroke, although the most common cause of CBS is CBD. Treatment and management are similar whichever term is used, focusing on symptom relief, communication, physical support and quality of life.

The NHS says there is currently no cure for CBD and no treatment to slow it down, but there are many things that can be done to help manage the symptoms. Care is provided by a multidisciplinary team, which may include a neurologist, physiotherapist, speech and language therapist, occupational therapist, social worker and a specialist neurology nurse, with a care plan agreed with you.

There are no medicines that treat CBD specifically, but medicines may help with muscle stiffness or contractions, jerky movements, memory (the medicines used to treat Alzheimer's disease such as donepezil or memantine may be used), irritability or depression, sleep problems, bladder problems, pain and anxiety, and bone strength. The NHS says people with CBD are generally sensitive to medicine side effects, so doses may start low and increase gradually.

Physiotherapy can advise on remaining safely mobile, strengthening, posture and breathing exercises to use when eating. Occupational therapy can advise on preventing trips and falls and arrange equipment such as walking frames, wheelchairs and aids for washing and dressing. Speech and language therapy can assess and treat speech and swallowing problems and advise on communication aids, and a dietitian can advise on altering food consistency. Feeding tubes may be recommended for severe swallowing problems, to be discussed with your family and care team.

Palliative care, which aims to relieve pain and other distressing symptoms and provide psychological, social and spiritual support, can be offered at any stage alongside other treatments, and many people make advance care plans for the future.

The NHS says CBD occurs when brain cells in certain parts of the brain are damaged as a result of a build-up of a protein called tau. The surface of the brain (the cortex) and a deep part called the basal ganglia are affected. Tau occurs naturally in the brain and is usually broken down before it reaches high levels, but in people with CBD it is not broken down properly and forms harmful clumps in brain cells.

CBD has been linked to changes in certain genes, but the NHS says these links are weak and the risk to other family members is very low. The sources reviewed do not describe any lifestyle or environmental cause.

The NHS says it can be difficult to diagnose CBD because there is no single test and it has similar symptoms to several other conditions. The diagnosis is based on the pattern of symptoms, and doctors try to rule out other conditions such as Parkinson's disease, stroke and Alzheimer's disease. It is usually made by a neurologist.

You are likely to be referred for brain scans, which may include an MRI scan (which can show shrinkage of certain areas consistent with CBD), a PET scan and a DaTscan. A short course of levodopa may be used, because it works very well in Parkinson's disease but not so well in CBD. Neuropsychological testing, a series of memory tests with words and pictures, evaluates the full extent of the impact on mental abilities.

The PSP Association adds that CBD itself can only be confirmed with certainty after death, by examining the brain, so doctors usually speak of probable CBD, and that researchers are developing tests for tau in spinal fluid and blood.

The NHS says CBD usually changes very slowly, and that the rate at which symptoms progress varies widely from person to person. As a result of complications such as swallowing difficulty, choking and aspiration pneumonia, it says the average life expectancy is around 6 to 8 years from when symptoms start, but that this is only an average and CBD is very variable.

The NHS says good care and assistance can help someone with CBD be more independent and enjoy a better quality of life, and that many people find it helpful to plan ahead with their doctors to make decisions about the later stages of the illness.

CBD is often confused with other movement disorders. The NHS says doctors try to rule out Parkinson's disease, and that a person's symptoms usually help to distinguish them, sometimes supported by a trial of levodopa. The PSP Association says asymmetric symptoms affecting one side first are typical of CBS and that CBD and PSP are related conditions it supports people with.

The NHS says being told you have CBD can be devastating and hard to take in, and that support from family and the care team can help. The PSP Association (PSPA) is the UK charity that provides information and support to people living with progressive supranuclear palsy (PSP) and CBD, including a helpline, support groups and information for carers. The NHS says many people, even doctors, have not heard of CBD, so PSPA information can help you explain it.

If you have CBD, your clinical team will pass information about you to the National Congenital Anomaly and Rare Disease Registration Service, which helps scientists look for better ways to prevent and treat the condition. You can opt out at any time.

On the NHS, CBD is usually diagnosed by a neurologist after GP referral, with ongoing care from a team that includes neurology nurses, therapists and palliative care. Social care support may be arranged through your local authority.

Some people seek a private neurology opinion or scan to clarify the diagnosis. Ensure reports are shared with your GP and NHS team so that your care plan stays joined up.