Corticobasal degeneration (CBD) is a neurodegenerative brain disease that has no known cause, treatment or cure. It affects nerve cells that control walking, balance, mobility, vision, speech, and swallowing.
CBD is rare, affecting an estimated 2000-3000 people in United States, of whom only 500-750 are diagnosed.
Corticobasal degeneration (CBD) is a rare neurological disease associated with progressive brain degeneration. The disease, also known as corticobasal ganglionic degeneration, leads to the loss of brain tissue in the cortex, or outer layer of the brain, especially the area in the upper, front section of the brain.
The brain tissue of patients with CBD show cell changes that also appear in patients with two other disorders — frontotemporal dementia and progressive supranuclear palsy.
These changes involve a brain protein called tau and may provide researchers with some initial clues regarding the causes of corticobasal degeneration. Currently, there are no known causes, such as toxins or infections.
Symptoms of Corticobasal Degeneration
The gradual loss of brain tissue and symptoms typically begin between ages 45 and 70. Initial symptoms include stiffness; shaky, slow or clumsy movements; and difficulty with speech and comprehension.
Other symptoms include:
- Balance — Difficulty walking and balancing
- Memory — Short-term memory problems, such as repeating questions or misplacing objects
- Muscle Control — Difficulty controlling muscles of the face and mouth
- Speech — Progressive difficulty speaking and difficulty comprehending language
- Symptoms related to muscle control usually begin on one side of the body and spread gradually to the other.
- Symptoms begin, on average, when an individual is in the early 60’s, but may start as early as in the 40’s. These include:
- Stiffness, shakiness, jerkiness, slowness, and clumsiness in either the upper or lower extremities
- Difficulty with speech generation (dysphasia)
- Difficulty with articulation (aphasia)
- Difficulty controlling the muscles of the face and mouth (dysarthria)
- Walking and balance difficulty
- Asymmetric onset of symptoms (occuring on one side of the body first then gradually moving to the other side)
- Memory or behavior problems
Below is a large collection of in-depth information on the disease including its background, symptoms and treatment options, among other things.
Early in the course of the disease, it may be difficult to distinguish corticobasal degeneration (CBD) from other neuro-degenerative diseases or forms of dementia. Diagnosis involves a comprehensive neurological exam, combined with one or more types of laboratory evaluations:
- Computerized tomography (CT)
- Magnetic resonance imaging (MRI)
These scan provide images of the brain in the areas most frequently involved in the disease — the upper and front sections of the cortex or outer layer of the brain, and the basal ganglia at the base of the forebrain, which is associated with functions such as motor skills and learning.
Currently, there are no treatments to slow the progress of corticobasal degeneration (CBD). Instead, individual symptoms are targeted with specific medications or therapy. For example, rigidity and difficulty walking may partially respond to treatments for Parkinson’s disease.
Muscle contractions and and twitching may respond to muscle relaxants or anti-seizure medications.
Memory and behavior problems may respond to treatments for Alzheimer’s disease or depression.
There is no treatment available to slow the course of corticobasal degeneration, and the symptoms of the disease are generally resistant to therapy.
Drugs used to treat Parkinson disease-type symptoms are sometimes tried, but often do not produce significant or sustained improvement for motor symptoms.
Some CBD patients benefit from the selective serotonin reuptake inhibitors (SSRIs) used in treating depression and/or the acetylcholinesterase inhibitors used in Alzheimer disease, which enhance the activity of neurotransmitters in the brain.
Clinicians may also employ antioxidants, such as vitamin E or coenzyme Q10, which are known to slow the progression of damage to brain cells in general. Medications may also be prescribed to diminish the tremor.
Maintaining a healthy lifestyle with physical and mental activity is generally recommended for patients with central nervous system degenerative diseases, as is a “heart healthy” diet.
Although there is no treatment for CBD, therapy does help to manage the symptoms, and hopefully one day we will be able to delay their progression.
Occupational and physical therapies provide passive range of motion in affected muscles, and help prevent contractures (paralysis of a muscle in the tense state) in rigid limbs. Speech therapy may help delay the progression of language symptoms.
It is important for caregivers and families to think about long-term management issues and identify a team of experts who can help with difficult medical, financial and emotional challenges. It is imperative to have a physician who is knowledgeable about frontotemporal degeneration and CBD.
Other medical specialists who may be helpful include: speech therapists, occupational and physical therapists, neuropsychologists, nurses (especially home-care nursing), and genetic counselors.
Occupational therapy may be used to design equipment that supports the activities of daily living and maintains functional independence.
Physical therapy is important for maintaining a patient’s range of motion. This may prevent pain and contraction or the shortening of muscles as well as help maintain mobility.
Key Pathologic Features
Upon autopsy, the brain tissue of corticobasal degeneration (CBD) patients is characterized by nerve cell loss, gliosis and atrophy (shrinkage) of the deeper layers in the posterior frontal and/or parietal lobes, and the substantia nigra.
Swollen (ballooned) nerve cells containing tau and phosphorylated neurofilament epitopes, similar to those seen in Pick’s disease, are a hallmark feature.
Scientists have recently determined that affected CBD brain cells contain deposits of abnormal forms of the protein tau. Tau is present in all neurons, and it plays important roles in the structure and function (metabolism) of neurons.
But in CBD, tau is abnormally phosphorylated, and this biochemical change keeps it from functioning properly.
CBD is almost always sporadic, developing by chance rather than being inherited. Some research has found associations with CBD and a specific form (variant) of the tau gene.
However, this information is not useful for the diagnosis of specific individuals because the tau forms are neither sensitive nor specific for this degeneration.
Corticobasal degeneration usually progresses slowly over the course of 6 to 8 years. During this time, the patient’s ability to live and function independently is diminished, leaving them dependent on others for activities of daily living.
Death in CBD is generally caused by pneumonia or other complications, such as sepsis (an infection throughout the body) or pulmonary embolism (a blood clot that blocks a major blood vessel in the lung).