What is corticobasal degeneration (CBD)?
Corticobasal degeneration, sometimes referred to as corticobasal ganglionic degeneration (CBGD), is considered to be part of the "Pick complex" of neurodegenerative diseases because it is clinically, genetically and pathologically similar to frontotemporal dementia (FTD). It is characterized by nerve cell loss and atrophy (shrinkage) of multiple areas of the brain including the cerebral cortex and the basal ganglia.
CBD typically occurs in patients aged between 45–70. Rarely, there is a family history of dementia, psychiatric problems or a movement disorder. The current estimates of 2000–3000 people affected by CBD in the US likely underestimates the frequency of this disorder.
When a diagnosis of CBD is suspected, it is important to refer the patient to a neurologist who is experienced with this disorder, because the constellation of symptoms can be unique. Significant advances in the understanding of CBD over the past 10 years have led to improved counseling, support and symptomatic treatments.
Signs & symptoms of corticobasal degeneration (CBD)
Patients with CBD usually present with either a movement disorder or cognitive deficits. As the disease progresses, most patients will develop both types of symptoms, often with a delay of 2-3 years.
The movement problems can look like Parkinson’s disease (PD). Unlike PD however, CBD patients typically do not typically improve with PD medicines, such as carbidopa-levodopa (Sinemet®), and many symptoms of CBD are not found in PD patients. A characteristic feature of movement symptoms in CBD is rigidity, although tremor is less common. Frequently symptoms begin insidiously in one hand, arm or leg.
Many patients will complain initially of a subtle change in sensation or an inability to make the affected limb follow commands. This latter deficit is called apraxia and may be confused for clumsiness or weakness. There may be difficulties in completing specific tasks, such as opening a door or brushing one’s teeth or using tools, like a can opener. When a leg is affected initially, a patient may have problems with complex movements such as dancing; or when more severe, a patient may begin to trip and fall. Some patients will experience an involuntary stiffening, twisting or contraction of the affected limb called dystonia. There may be uncontrolled jumping of the limb when it is tapped gently or when the patient is startled, called myoclonus.
Finally, CBD patients often complain that the affected limb feels like it is not a part of their body, a sensation called alien limb. Sometimes an alien limb will move on its own, in an uncontrollable way. For example, an alien hand will rise to touch the patient’s face. Alien limb phenomenon was dramatized by the actor Peter Sellers in the film Dr. Strangelove.
Patients with CBD who present with cognitive difficulties are often initially diagnosed with frontotemporal dementia or Alzheimer's disease. It is only after they develop movement symptoms that the diagnosis of CBD is considered. Occasionally, a diagnosis of CBD is not apparent until a patient’s brain is examined at autopsy and shows "ballooned" neurons, protein aggregations (neuronal inclusions) and other abnormalities resulting from abnormal accumulation of the tau protein.
Progressive difficulty with language is a common cognitive complaint in CBD. This most commonly involves difficulty with expression of language, such as word finding difficulty or naming problems. Reading, writing and simple mathematical calculations may also be impaired.
Personality changes, inappropriate behavior, repetitive and/or compulsive activities similar to those seen in FTD are also common in CBD. Short-term memory problems, such as repeating questions or misplacing objects are less common.
Increasingly it has become evident that CBD presents in a wide-variety of ways, with the majority of patients beginning with either apathy, trouble with speaking or motor rigidity without tremor.
Progression of corticobasal degeneration (CBD)
Corticobasal degeneration usually progresses slowly over the course of 6–8 years. Movement symptoms tend to progress slowly from one side of the body to the other or from leg to arm on the same side of the body.
Treatment of corticobasal degeneration (CBD)
At this time, there is no specific treatment for CBD. Instead individual symptoms are targeted with specific medications. For example, rigidity and difficulty walking may partially respond to treatments for Parkinson’s disease. Dystonia and myoclonus may respond to muscle relaxants or anti-seizure medications. Memory and behavior problems may or may not respond to treatments, such as donepezil, for Alzheimer's disease. Depression and/or anxiety can be treated with an antidepressant, such as sertraline, citalopram or escitalopram.
Physical therapy and stretching exercises may relieve rigidity, prevent contractions and deformities, and maintain muscle strength. Assistive devices like canes or walkers can be helpful. Speech, physical and occupational therapy may be beneficial.
Resources for corticobasal degeneration (CBD)
- NINDS Corticobasal Degeneration Information Page
- CurePSP Foundation for PSP | CBD and Related Brain Diseases is dedicated to assisting patients and their families, increasing public awareness, educating healthcare professionals and supporting research toward better diagnosis, effective treatments, and eventual cures of progressive supranuclear palsy (PSP), CBD and multiple system atrophy (MSA).