CJD does not cause any symptoms at first. The first symptoms to appear include slow thinking, difficulty concentrating, impaired judgment and memory loss. These types of symptoms can overlap with some other neurological problems, such as Alzheimer's disease or Huntington's disease. Soon after these symptoms appear, they lead to severe, progressive dementia (mental decline) associated with self-neglect, apathy or irritability and prominent muscle spasms. Patients become completely bedridden as brain injury worsens, and eventually lapse into coma. Comatose patients may die as a result of infection associated with being immobile, such as pneumonia.
The first symptom of CJD is rapidly progressive dementia, leading to memory loss, personality changes and hallucinations. This is accompanied by physical problems such as speech impairment, jerky movements (myoclonus), balance and coordination dysfunction (ataxia), changes in gait, rigid posture, and seizures. The duration of the disease varies greatly, but sporadic (non-inherited) CJD can be fatal within months or even weeks (Johnson, 1998). In some people, the symptoms can continue for years. In most patients, these symptoms are followed by involuntary movements and the appearance of an atypical diagnostic electroencephalogram tracing.
The symptoms of CJD are caused by the progressive death of the brain's nerve cells, which is associated with the build-up of abnormal prion proteins. When brain tissue from a CJD patient is examined under a microscope, many tiny holes can be seen where whole areas of nerve cells have died. The word ‘spongiform’ in ‘transmissible spongiform encephalopathies’ refers to the ‘spongy’ appearance of the brain tissue.
Some symptoms of CJD can be similar to symptoms of other progressive neurological disorders, such as Alzheimer’s or Huntington’s disease. However, CJD causes unique changes in brain tissue which can be seen at autopsy. It also tends to cause more rapid deterioration of a person’s abilities than Alzheimer’s disease or most other types of dementia.
There are several known variants of CJD. These variants differ somewhat in the symptoms and course of the disease. For example, a variant form of the disease-called new variant or variant (nv-CJD, v-CJD), described in Great Britain and France-begins primarily with psychiatric symptoms, affects younger patients than other types of CJD, and has a longer than usual duration from onset of symptoms to death. Another variant, called the panencephalopathic form, occurs primarily in Japan and has a relatively long course, with symptoms often progressing for several years. Scientists are trying to learn what causes these variations in the symptoms and course of the disease.