No single test can be used to 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.
Because 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.
If you have symptoms that suggest that there is something wrong with your brain, it is likely that you will be referred for brain imaging studies.
These may include:
- a magnetic resonance imaging (MRI) scan - strong magnetic fields are used to produce a detailed image of the inside of the brain
- a 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, such as a brain tumour and 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 is not the case for people with CBD, and levodopa usually only has a limited effect in improving symptoms.
It is also likely that you will be referred to a neurologist (nerve and brain specialist) for neuropsychological testing.
This involves having a series of tests that are designed to evaluate the full extent of your symptoms and their impact on your mental abilities.
The tests will look at abilities such as:
- ability to understand language
- the ability to process visual information, such as words and pictures
Most people with CBD have a distinct pattern in terms of their mental 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 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 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 will require full-time care and most likely assistant technology, such as a wheelchair, to help with activities.
Read a practical guide to caring and more about adjusting to a disability.