Corticobasal degeneration (CBD)
by André Delacourte
Corticobasal degeneration (CBD) is a rare neurological disease in which parts of the brain deteriorate or degenerate. CBD is also known as corticobasal ganglionic degeneration, or CBGD.
Several regions of the brain degenerate in CBD. The cortex, or outer layer of the brain, is severely affected, especially the fronto-parietal regions, located near the center-top of the head. Other, deeper brain regions are also affected, including parts of the basal ganglia, hence the name corticobasal degeneration.
Corticobasal ganglionic degeneration (CBGD)
Symptoms and course
Initial symptoms, which typically begin at or around age 60, may first appear on one side of the body (unilateral), but eventually affect both sides as the disease progresses. Symptoms include signs of parkinsonism such as poor coordination, akinesia (an absence of movements), rigidity (a resistance to imposed movement), and disequilibrium (impaired balance); and limb dystonia (abnormal muscle postures). Other symptoms such as cognitive and visual-spatial impairments, apraxia (loss of the ability to make familiar, purposeful movements), hesitant and halting speech, myoclonus, and dysphagia (difficulty swallowing) may also occur.
CBD is a progressive disease, meaning that the symptoms worsen over time. Over the course of one to several years, most people with CBD gradually worsen, with symptoms progressing to involve upper and lower extremities and other body regions. Symptoms of advanced CBD include:
- parkinsonism (rigidity, slow movements, postural instability)
- myoclonus (sudden, brief jerky movements)
- dystonia, including blepharospasm
- speech difficulty
- mild-to-moderate cognitive impairment (memory loss, difficulty planning or executing unrehearsed movements, dementia)
- sensory loss
- alien hand/limb phenomenon (difficulty controlling the movements of a limb, which seems to undertake movements on its own, sometimes combined with a feeling that the limb is not one's own)
The age of onset is around 60 years old. The duration of the disease is between 5 and 10 years.
Causes and risk factors
CBD is essentially sporadic. A degeneration affecting many subcortical nuclei and spreading into the neocortex in the frontal and parietal areas with an aggregation of tau protein in affected areas within neurons and in astrocytes. Genetic risk factor is H1H1 in the tau gene. Belongs to the 4R tauopathies (aggregation of tau isoforms with 4 repeats) (Sergeant N. et al, 1999).
Genetic risk factor linked to tau gene (Baker M. et al, 1999).
Similar to PSP: 2-6/100.000.
An EEG (electroencephalogram) may show changes in brain function over time that are consistent with the neuro-degeneration. CT or MRI scans can also be used in this way, providing images of asymmetric atrophy of the fronto-parietal regions of the brain's cortex, the regions most frequently involved in the disease. (Litvan I. Et al, 1997).
Clinical features. A difference between PSP and CBD is described at the neuro-pathological level (glial tufted plaques for PSP or astrocytic plaques for CBD).
Care and treatment
Unfortunately, there are no drugs or other therapies that can slow the progress of the disease, and very few that offer symptomatic relief. Tremor and myoclonus may be controlled somewhat with drugs such as clonazepam. Baclofen may help reduce rigidity somewhat. Levodopa and other dopaminergic drugs used in Parkinson's disease are rarely beneficial, but may help some CBD patients.
Ongoing research / Clinical trials
Corticobasal ganglionic degeneration (CBGD) caregivers report http://www.tornadodesign.com/cbgd/index.htm
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Last Updated: Friday 09 October 2009