Corticobasal Degeneration

Definition

Corticobasal degeneration (CBD) is a rare, progressive, neurodegenerative disease that causes movement disorders and dementia.

Description

CBD occurs when brain cells in two areas of the brain—the cortex and the basal ganglia—die off. The cause of this neurodegeneration is unknown. CBD is also called cortical basal degeneration and corticobasal ganglionic degeneration.

Demographics

It is not known exactly how many people have CBD. In the United States, the number is probably fewer than 10,000. Men and women are equally affected. Symptoms usually appear when a person is 50 or 60 years old.

Causes and symptoms

The ultimate cause of CBD is unknown. No genes have been found to be responsible, and no environmental or other risk factors have been identified. The brain areas affected are the cerebral cortex and the basal ganglia. The cerebral cortex is the center of mental activities such as planning, memory, language, and reasoning. The basal ganglia help control movements.

The symptoms of CBD may begin with either movement disorders or cognitive disorders. The movement disorders seen in CBD are similar to those in Parkinson's disease (PD), and CBD is often initially misdiagnosed as PD. In CBD, movements become slow and stiff, and may be accompanied by sustained abnormal postures (dystonia) or sudden violent jerks (myoclonus). Cognitive symptoms include memory impairment, loss of judgment, and difficulty planning or executing movements. Additional features may include impaired speech, and the "alien hand" phenomenon, in which the patient feels disconnected from, and not in control of, a hand or limb. Loss of sensation may also occur.

Diagnosis

Corticobasal degeneration is diagnosed with a neurological exam (testing of reflexes, coordination, sensation, etc.) and neuroimaging studies, including computed tomography (CT) scan and magnetic resonance imaging (MRI) to detect characteristic loss of brain tissue. Neuropsychological testing is also usually done to determine the kind and degree of cognitive impairment.

Treatment team

The treatment team includes a neurologist, neuropsychologist, speech/language pathologist, geriatric medicine specialist, and possibly a physical or occupational therapist.

Treatment

There are no treatments that can slow or reverse the course of CBD. Some symptoms can be lessened with drugs, although these are inconsistently effective and become less effective as time passes.

Drugs used against PD are often prescribed, although they are rarely as effective in CBD. These drugs include levodopa and dopamine agonists, as well as anticholinergics such as trihexyphenidyl. Drugs used for Alzheimer's disease may also be tried for the cognitive symptoms.

A speech/language pathologist can help the patient with swallowing difficulties, although over time this problem will become worse and the patient may require the use of a feeding tube. The same specialist can advise about the use of assistive communication devices to improve communication as the ability to speak is lost.

Prognosis

Ability to move without a wheelchair is usually lost within five years of diagnosis. Within 10 years, swallowing difficulties often put the patient at risk for developing aspiration pneumonia, or lung infection from food in the airways. Death from pneumonia is common in CBD.

WEBSITES

WE MOVE. (April 19, 2004.) <http://www.wemove.org>.

National Institute of Neurological Disorders and Stroke (NINDS). Corticobasal Degeneration Information Page. (April 19, 2004). <http://www.ninds.nih.gov/health_and_medical/disorders/cortico_doc.htm>.

Richard Robinson