CBD: SOME ANSWERS
Lawrence I. Golbe, MD
Professor of Neurology, Rutgers Robert Wood Johnson Medical School Director of Clinical Affairs and Scientific Advisory Board Chairman, CurePSP
What is corticobasal degeneration( CBD)?
As its name states, corticobasal degeneration is a loss of brain cells emphasizing the cerebral cortex and the basal ganglia. The cortex is the outer layer of the cerebrum, the gray matter where most thinking, speech, and sensory perception occur. The basal ganglia are also gray matter, but they’ re deeper in the cerebrum and they coordinate movement. Basal refers to the base of the brain; ganglia are collections of brain cells in one location devoted to a single purpose.
What are its main signs and symptoms?
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CBD is considered one of the“ parkinsonian” disorders, or“ parkinsonisms.” There are about a dozen such diseases, all of which produce some degree of slowness, muscle stiffness, balance problems, and sometimes tremor. Most people with CBD have these things, but in addition they have unusual difficulty performing complex limb movements, such as cutting food, buttoning, or typing. There is often a tendency to hold part or all of a limb in a fixed posture called dystonia. There can also be very rapid, irregular, small movements of muscles called myoclonus.
The unusual feature about CBD is that it is almost always very asymmetric, with one side affected much earlier and worse than the other. In half of people with CBD, it’ s the left side, and in half, it’ s the right. The side affected has no relationship to the person’ s handedness.
An important part of CBD that is often difficult for patients and families to understand is apraxia. This is the loss of the ability to perform a complex movement that required some practice to learn in the first place. Manual tasks or gestures become clumsy, and walking can become frozen for several seconds at a time. Common examples of apraxia are losses of the ability to use eating utensils or to manage buttons. An unusual but dramatic type of apraxia is alien limb phenomenon, where one hand seems to belong to someone else and can perform actions that oppose the person’ s intentions. Another unusual type of apraxia is arm levitation, where one arm tends to move upward involuntarily.
Contributing to the movement problem of CBD is a sensory problem. It’ s not a simple loss of sense of touch but an inability to interpret spatial complexity involving touch. This can take the form of an inability to recognize common objects by feel alone or the inability to know the position of a finger or a limb in space.
How does CBD start?
The first symptom is usually apraxia in one hand, but sometimes it starts as Parkinson’ s disease does, with general slowing and stiffness, perhaps with a mild tremor and slurred speech. Over the next few months, the symptoms worsen, and the dystonia may start. Sometimes CBD starts with aphasia, which is difficulty producing or understanding language.