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, motor neurone disease and Alzheimer's disease.
Your doctor will need to carry out assessments of your symptoms, as well as other tests and scans.
The diagnosis must be made or confirmed by a consultant with expertise in CBD. This will usually be a neurologist (specialist in conditions affecting the brain and nerves).
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:
- magnetic resonance imaging (MRI) scan – where a strong magnetic field and radio waves are used to produce detailed images of the inside of the brain
- positive emission tomography (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.
Scans that show the build-up of the tau protein in the brain that's associated with CBD are being developed.
Ruling out Parkinson's disease
A person's symptoms and signs 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.
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:
- 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 on 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 0110 122, or by emailing: email@example.com.
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.