Overlap with Corticobasal Degeneration (CBD)
Corticobasal degeneration (CBD) is a progressive neurodegenerative disease closely related to frontotemporal dementia (FTD). CBD is associated with atrophy (shrinkage) of various regions of the brain, particularly the frontal lobes as well as more posterior regions. CBD was first recognised some 40 years ago as a cause of motor problems but has since been shown to produce symptoms identical to those seen in FTD.
This disease usually begins between the age of 50 and 70 with some of the following symptoms:
Motor symptoms: Symptoms include rigidity and slow movements, a tendency to fall, sudden, brief jerky movements (known as myoclonus), and abnormal posture of limbs. These symptoms typically affect one side of the body more than the other and are often confused with Parkinson’s disease.
Apraxia: This is an inability to carry out complex movements in the absence of weakness or wasting, usually involving the hands. Apraxia is due to the fact that the brain is unable to send the right messages to the limb. In some patients the hand may behave as if it has a will of its own (so called “alien limb syndrome”), leading it to wander and interfere with the other hand.
As the disease progresses, many patients with CBD develop prominent apathy, loss of empathy towards others, and poor decision making. Other patients develop features of Progressive Non-Fluent Aphasia (PNFA), characterised by difficulty speaking (due to poor articulation), slurring of words and grammatical errors. Comprehension is typically normal. Problems with writing and spelling are often a pronounced early feature. (See other fact sheets)
The majority of patients with CBD present with motor problems. In some patients, however, cognitive, emotional and/or language problems may be the first signs. It can sometimes be very difficult to separate CBD from Alzheimer’s disease and from Parkinson’s disease which can also present with coordination and speech problems.
No single test exists for CBD. It is diagnosed on the basis of clinical assessment, neuropsychological testing and brain imaging to detect the telltale pattern of brain atrophy. CBD has a slow progression over a number of years. No cure or treatment currently exists for this disease and its management requires the expertise of health practitioners, neuropsychologists, and speech and occupational therapists. It is, in general, not an inherited disorder.
In the brain, CBD causes a loss of brain cells (neurons) in the frontal and parietal lobes. When sections of the brain stained with special dyes, are looked under the microscope, CBD patients show an increase of a protein called ‘tau’. Tau is also one of the proteins implicated in the causation of FTD. The pathology of CBD is extremely similar to classic Pick’s disease with accumulations of ‘tau’ protein within neurons which look very similar to Picks bodies.
