How many people are diagnosed with CBD? CBD is very rare. The current estimate is 2,000-3,000 people diagnosed with CBD in the United States. This compares with 30,000-40,000 people with progressive supranuclear palsy( PSP), which is a different but related atypical parkinsonism disorder; about 1 million with Parkinson’ s disease; and 5 million with Alzheimer’ s disease. However, these numbers for CBD are likely underestimates because many people with CBD are misdiagnosed with another condition, such as PSP or Parkinson’ s disease.
What are the main symptoms of CBD? CBD shares with Parkinson’ s disease its slowness, muscle stiffness, balance problems and sometimes tremor. Most people with CBD also have problems performing complex movements such as cutting food, buttoning or typing. These types of symptoms usually begin by affecting one hand. People with CBD tend to hold part or all of a limb in a fixed posture, called dystonia. An important aspect of CBD is the asymmetry of its symptoms, meaning that it almost always starts on one side of the body. Over time, the other side can become affected, but the first side always remains worse. There can also be very rapid, irregular, small movements of muscles, called myoclonus.
CBD can cause a symptom called apraxia, which is the loss of ability to perform complex, familiar, previously learned movements. Manual tasks or gestures become clumsy, and walking can become frozen for several seconds at a time. An unusual, dramatic type of apraxia seen sometimes with CBD is alien limb phenomenon, where one hand can feel to the person as if it belongs 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. Apraxia can produce a wandering of the limb attempting to find its target that can resemble an involuntary movement. Apraxia in some people with CBD also affects speech, producing pauses and slurring, as well as control of the trunk, causing difficulty sitting down, standing up and maneuvering in bed.
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A sensory problem also contributes to the movement problem of CBD. It’ s not a simple loss of sense of touch but an inability to interpret spatial complexity involving touch. This problem 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. Similar to the other symptoms described above, this sensory problem is also often asymmetric, meaning that it affects one side of the body much more than the other. Sometimes there is also a problem with spatial reasoning in general, causing difficulty in things like dressing or finding one’ s way around familiar places.