Although there are species barriers, the spongiform diseases are generally considered to be caused by similar processes. CJD and scrapie had been described for many years when transmission of the human form of the disease was first accomplished by intracerebral inoculation of primates with CNS tissues from patients dying of kuru, a spongiform encephalopathy associated with ritual endocannibalism in a tribe then residing in the remote highlands of New Guinea. The diagnosis of CJD is based on clinical findings. In addition, patients may complain of insomnia, fatigue, and problems with vision. In some instances, persons with CJD may be cortically blind.
Neurologic examination shows evidence of pyramidal tract involvement and occasional muscle atrophy.
Other findings include cerebellar ataxia and seizures. Specific diagnostic findings cannot be obtained from either MRI or CSF examination, but the electroencephalogram may demonstrate characteristic triphasic forms. CJD is uniformly fatal, usually within two years of onset. In contrast, transgenic mice that were engineered to express the PrP gene from other species, including humans, became particularly susceptible to the diseased brain harvested from the species supplying the transgene. As there are species barriers to the transmission of spongiform change, these latter experiments suggest that the transgene is responsible for the disease process.