Most patients with CJD first show vague, non-specific physical and mental symptoms. This phase is followed by rapidly progressive dementia accompanied by motor disturbances such as loss of coordination and muscle jerking known as myoclonus. However, the symptoms of CJD vary widely in different patients. Early in CJD, most patients experience some combination of the following symptoms:
- Difficulty sleeping
- Decreased appetite
- Failing memory
- Behavior or personality changes
- Impaired judgment
- Strange physical sensations
- Visual disturbances
- Lack of coordination
- Involuntary movements, especially muscle jerking known as myoclonus
With time, patients rapidly lose their ability to think clearly and carry out daily activities. Involuntary muscle jerking known as myoclonus can occur at any point in the disease, although it is most common in the middle or late stages. Patients may develop additional symptoms such as weakness in the arms or legs, blindness, and seizures.
As the disease progresses, mental deterioration becomes so pronounced that patients can no longer perform daily activities. In the final stages, the patient loses all mental and physical function, and ultimately lapses into a coma. Patients usually die from an infection or other bodily illness (e.g., pneumonia) because the dementia prevents them from communicating their symptoms.
The symptoms of nvCJD differ somewhat from those of the other forms of the disease. Patients with nvCJD are more likely to experience depression, anxiety, and other psychiatric symptoms, as well as sensory abnormalities. As the disease progresses, patients lose coordination, and experience involuntary muscle jerking (myoclonus) and other motor problems seen in the other forms of CJD. Unlike in these other forms, patients may not show dementia until late in the course of the disease. While symptoms of memory loss, reduced mental capability, and agitation can also occur in other dementias, such as Alzheimer's or Huntington's diseases, CJD causes a more rapid deterioration of a person's abilities than all other types of dementia.
The most common form of CJD—sporadic CJD—has no proven risk factors. However, a new study indicates a possible connection between frequency of surgical operations and living or working on a farm. A 1999 study from Australia (published in the British medical journal The Lancet) raised the possibility that the risk for sporadic CJD increases with the number of surgical operations one has in one's lifetime. The study also suggested that people who have lived or worked on farms for 10 years or more may also be at higher risk. Additional studies are needed to confirm these and other potential risk factors for sporadic CJD.
People with a family history of CJD have an increased risk of developing familial CJD. A person who has only a single known family member with CJD may not be at increased risk for familial CJD—the likelihood is that the case represents an isolated occurrence. Moreover, simply living with a person with CJD does not increase one’s risk of contracting the disorder. However, in an extremely small number of families, CJD appears in multiple generations. Members of such families have a greater risk of developing CJD than the general population
People most at risk for infectious CJD are those who received brain dura mater transplants or growth hormone taken from human pituitary glands in the 1980s. Since the link between CJD and human growth hormone was discovered, growth hormone is no longer harvested from human pituitary glands. There are also reported cases of CJD transmission through corneal transplants. However, cornea donors have been routinely screened for CJD risk since 1980, and cornea transplantation is no longer considered to be a significant risk factor.
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