Neuropathology of spongiform encephalopathies in humans

The historical aspects and classification of human spongiform encephalopathies are reviewed and the newer concept of 'prion dementias' is explored. Guidelines for safe laboratory and autopsy handling of spongiform encephalopathy tissues are outlined: this includes an update on strategies which are currently thought to be effective in decontamination. A wide ranging review of the pathology of the various human spongiform encephalopathies includes newly emerging data on microglia, and cell-specific and neurodegenerative proteins. A large section of this chapter is devoted to the methodology of immunocytochemical demonstration of PrP in tissue sections, and the dilemmas inherent in interpretation. Clinicopathological correlations are provided for classical cases of spongiform encephalopathy, together with the newly recognised atypical dementias associated with PrP gene mutations. The pathology of iatrogenic cases of CJD is described. The chapter concludes with problems in differential diagnosis, and discussion of the histopathological features which help to resolve diagnostic dilemmas.