Neuropathological Diagnosis of Human Prion Disease: PrP Immunocytochemical Techniques

Routine histological examination of cases of Creutzfeldt-Jakob disease (CJD) reveals a spectrum of pathological involvement, particularly with regard to the extent and localization of spongiform change. Although there is no difficulty in confirming a diagnosis of CJD in cases with widespread and severe spongiform change involving the cortical gray matter or cerebellar molecular layer, all too often the cortex may be only minimally or focally affected, and in some cases pathological changes are largely confined to the basal ganglia or cerebellum. Unless wide-ranging pathological examination is undertaken, the diagnosis of CJD may be missed in such cases. Thus is a particular problem in the interpretation of cortical biopsies in cases of suspected CJD and is one reason why biopsy in such cases is now discouraged (1 ). In addition, there are other conditions that give rise to spongy appearances in the gray matter (2 ) and the difficulties of achieving a firm diagnosis of CJD, based on conventional histological appearances, have been outlined in Chapter 3. Occasional reports of the coexistence of CJD with other dementing illnesses, particularly Alzhelmer disease, also add to the dragnostic difficulties (3 ). CJD is a rare disease (0.5 cases/million of the population/yr) and it is likely that individual experience of the possible range of CJD pathological changes will be limited. For all of these reasons, it would be useful to develop some additional method of confirming the diagnosis of CJD in tissue sections. Since it is now known that CJD and related diseases are associated with accumulation in the brain of a protease-resistant protein known as prion protein (4 ), the demonstration of prion presence in suspected cases would represent such a devolopment.