Diagnosis - Corticobasal degeneration

It can be difficult to diagnose corticobasal degeneration (CBD), as there's no single test for it, and the condition can have similar symptoms to a number of others.

A diagnosis of CBD will be based on the pattern of your symptoms. Your doctor will also try to rule out conditions that can cause similar symptoms, such as Parkinson's disease, a stroke and Alzheimer's disease.

Your doctor will need to carry out assessments of your symptoms, as well as other tests and scans.

The diagnosis will usually be made by a neurologist (specialist in conditions affecting the brain and nerves).

Brain scans

If you have symptoms of CBD that suggest there's something wrong with your brain, it's likely you'll be referred for a brain scan.

Types of scan that you may have include:

• MRI scan – where a strong magnetic field and radio waves are used to produce detailed images of the inside of the brain
• PET scan – a scan that detects the activity of the brain
• a DaTscan – to measure the amount of a chemical called dopamine that your brain is making

These scans can be useful in ruling out other possible conditions, such as brain tumours or strokes.

MRI scans can also detect abnormal changes to the brain that are consistent with a diagnosis of CBD, such as shrinkage of certain areas.

Brain scans are also being developed to show the build-up of a protein called tau. This is associated with CBD.

Ruling out Parkinson's disease

A person's symptoms usually help distinguish CBD from Parkinson's disease, but sometimes tests may be used to support the diagnosis and rule out other possible conditions.

You may be prescribed a short course of a medication called levodopa. This typically works very well in Parkinson's disease, but not so well in CBD.

If it doesn't lead to a significant improvement in your symptoms, it can help your doctor distinguish CBD from Parkinson's disease.

Neuropsychological testing

It's also likely you'll be referred to a neurologist and possibly also a psychologist for neuropsychological testing.

This involves having a series of "memory tests" with words and pictures. They're designed 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
• the processing of visual information, such as words and pictures
• numbers and counting

Most people with CBD have a distinct pattern of difficulties with these tests.

The memory of previously learned facts and the person's own life story is generally maintained.

Coping with a diagnosis

Being told that you have CBD can be devastating and difficult to take in.

You may feel numb, overwhelmed, angry, distressed, scared or in denial. Some people are relieved that a cause for their symptoms has finally been found. There's no right or wrong way to feel – everybody is different and copes in their own way.

Support from your family and care team can help you come to terms with the diagnosis.

The PSP Association (PSPA) can give you information and practical advice about living with CBD, as well as providing support to help you cope with the emotional impact of the condition.

You can get in touch with the PSPA by calling their helpline on 0300 011 0122, or by emailing: helpline@pspassociation.org.uk.

You may find that many people – even the doctors you meet – have not heard of CBD. The PSPA has online and printed information for patients, their families and professionals.