Pathology Of Prion Diseases:
During the incubation period and active clinical phase of prion diseases, PrP TSE is probably present (and can transmit the disease) in all tissues and body fluids, especially brain, nerves, and skeletal muscle. Pathology develops only in the brain. Initially, intracytoplasmic vacuoles appear in neurons. As the disease progresses, vacuolization becomes more pronounced and the cortical neuropil develops a spongy appearance, hence the term spongiform encephalopathy .
Advanced cases show neuronal loss, gliosis, and brain atrophy. Cerebellar atrophy is usually severe. Unlike most cerebellar degenerations, there is more pronounced loss of granular neurons than Purkinje cells. There is no inflammation. The CSF is normal. The changes are confined to the gray matter (the primary pathology involves the neuronal body). In some prion diseases, PrP TSE precipitates as amyloid plaques.
