​Corticobasal Degeneration (CBD)

Corticobasal degeneration (CBD) is a rare and gradually progressive neurodegenerative disorder that is difficult to diagnose and treat because its symptoms vary and are similar to those of other neurological disorders. The age of the disease onset is often in the 60s, but ranges from 45 to 77 years.

Symptoms

In corticobasal degeneration (CBD), areas of your brain, including the cerebral cortex and basal ganglia, shrink and your nerve cells decline and die over time. This leads to increasing difficulty in movement on one or both sides of the body.

CBD can cause poor coordination, stiffness, thinking (cognitive) difficulties, speech or language difficulty, or other problems.

There are four types of CBD, depending on the location of the underlying lesions:

Corticobasal syndrome (CBS) may be characterized by gradual progressive onset of motor symptoms affecting one side of the body that could include: parkinsonism characterized by stiffness (rigidity) and slowness of movements (bradykinesia); sustained muscle contractions causing abnormal postures (dystonia) and/or involuntary jerks (myoclonus).

In addition or alternatively, patients may have cognitive symptoms that include inability to execute or carry out learned purposeful movements without clear motor or sensory causes (ideomotor apraxia), feeling that a limb is foreign or has a mind of its own (alien limb phenomenon), language disturbances (aphasia), and/or difficulties with visual perception and spatial relationships of objects.

Speech can be affected and changed in different ways, including reduced volume, monotone pitch, fluctuating speech articulation, shallow inhalations, and slow rate of speech punctuated with rapid bursts or other changes.

CBS can also opccur in other neurodegenerative disorders such as progressive supranuclear palsy or an atypical form of Alzheimer’s disease. Laboratory studies may help rule out Alzheimer’s disease.

Frontal behavioral-spatial syndrome is characterized by behavioral or personality changes that include loss of interest in doing things (apathy), irritability and disinhibition. Patients may also show difficulties in planning, multitasking, or retrieving information. Patients with CBD may have visuospatial deficits characterized by difficulties understanding and conceptualizing visual representations and spatial relationships in learning and performing tasks.

Nonfluent/agrammatic variant of primary progressive aphasia is mainly characterized by progressive language difficulties characterized by an effortful, agrammatic speech in which patients may use simplified sentence structures and make errors in tense, number or gender. Patients may have a distorted speech production (apraxia of speech). There is usually a preserved single word comprehension.

Progressive supranuclear palsy syndrome (PSPS) has symptoms described as classically as PSP (Richardson syndrome). Learn more about profressive supranuclear palsy
 
Currently, there are no laboratory markers for diagnosis of CBD, but imaging and cerebrospinal studies are used to rule out other disorders.

Causes

CBD is labeled as a “tauopathy” because a cell protein that normally exist in the walls of the cells or nourishment pipes called “tau” aggregates abnormally inside the neurons and other brain cells — astrocytes and oligodendroglia. CBD is usually a non-hereditary (sporadic) disease, although rare familial cases of CBD have been reported. In CBD as in other tauopathies such as PSP there are polymorphisms in the tau gene that suggest there may be a genetic basis or at least a predisposition for this disorder. There have been no epidemiological studies of environmental or occupational risk factors.

Treatment

Pharmacological Management

There are no treatments that can stop or slow the progressive nature of CBD. Treatment is targeted at reducing the symptoms, improving the quality of life and preventing complications.

Pharmacologic therapies for the motor symptoms have limited benefit. Levodopa is usually not effective in improving the parkinsonism in CBD, but the poor responsiveness to levodopa therapy may support the diagnosis. Botulinum toxin can improve the dystonia and is usually used to treat it if there is pain or there are difficulties in cleaning the patient. There are several therapies that could improve the myoclonus, if significant, including benzodiazepines. If there is no observed benefit from these treatments, they should be tapered to avoid undesired side effects.

There are no known therapies that could improve the cognitive disturbances patients with CBD experience. Cholinesterase inhibitors (such as donepezil, rivastigmine, or galantamine) are not useful in CBD. However, depression, which is common, should be treated with an appropriate antidepressant medication as early as it is recognized.

Non-Pharmacological Management

Walking devices such as a weighted walker could prevent falls. However, using a walking device may be difficult when patients have apraxia.

Physical therapy may help with patients’ balance and gait disturbances. It may also be helpful to avoid a rotator cuff syndrome. Orthotic splinting may also reduce contractures and relieve pressure from tightly clinched fingers pressing into the palm. Occupational therapy can be beneficial in assisting with devices for eating and grooming and other adaptive measures. Similarly, speech therapy could be helpful to diagnose and manage speech and swallowing disturbances.

The care for CBD patients is difficult and demanding. Attention should be given to cues that the family is in distress, and referrals for respite care, in-home health assistance, hospice, and counseling should be made to support the families and caregivers and relieve caregiver burden and distress. Treatment of CBD is aimed at safety, symptom management, and patient and family supportive measures.

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Also see: San Diego Rady Children's Hospital Neurology

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