Corticobasal syndrome: a type of dementia affecting movement and thinking

Corticobasal syndrome (CBS) is a very rare form of dementia, estimated to affect just 5 in every 100,000 people. However, this figure may not be accurate as CBS is often misdiagnosed as a range of other conditions because the varied symptoms overlap with several other diseases. There is no single test to diagnose CBS, so other conditions must be ruled out first.

People with CBS experience physical symptoms that overlap with conditions like Parkinson’s disease and progressive supranuclear palsy. However, the tremors common in Parkinson’s disease are less commonly seen in CBS.

Some movement difficulties that occur in people with CBS include a lack of coordination, rigidity, jerky movements, and alien limb sensation where the affected limb may feel detached from the body and experience complex, unintentional movements. These movement issues commonly initially affect one side of the body, spreading to the other as the disease progresses.

CBS is also characterised by cognitive symptoms, which are issues with thinking skills. These include difficulty planning or carrying out a plan, inability to multitask, problems with simple calculations and language difficulties like trouble recalling words, and slow or slurred speech. Some of these things overlap with frontotemporal dementia and Alzheimer’s disease, leading people with CBS to be diagnosed with these conditions by mistake, especially if the physical symptoms of CBS are not present yet.

In the brain, CBS is characterised by shrinkage of the cortex, the outer layer of the brain which is responsible for more complex thinking skills. The other main area affected is the basal ganglia, which controls movement. You can read more about different brain areas in this blog post.

The damage to these areas of the brain is caused by an overproduction of a protein called tau, which you can read more about in this blog post. However, scientists don’t yet understand why or how tau damages brain cells in CBS.

As with most dementias, there is no cure for CBS yet. Cholinesterase inhibitors like donepezil – a type of drug commonly prescribed for people with Alzheimer’s disease – can be helpful to ease the cognitive symptoms. Unfortunately, the drugs used to treat movement disorders like Parkinson’s disease haven’t proved to be very effective in treating people with CBS.

Non-medical treatment like occupational therapy and physical therapy may help people with CBS to maintain their physical functioning for longer. Plus, speech therapy delivered early enough can help delay speech and language difficulties.

CBS is most common in people aged 60-80, and has been seen in people in their 40s, but never in anyone younger that 40. If you think you could be affected by CBS, Rare Dementia Support can help offer advice and support.