Prion diseases:
Prions are basically infectious proteins with long incubation period ranging from months to years. Normal prion protein is depicted as PrPc. Normally it has an alpha helical confirmation and is protease sensitive. Due to infections or sporadic most commonly causes these proteins undergo a conformational change where it attains Abeta helical structure and becomes resistant to protease degradation known as PRPSc. This protein can get misfolded and deposits in the neurons causing neuronal damage.
The characteristic damage is seen histologically as a cluster of grape like vacuoles and this is known as spongiform encephalopathy. This is because the damaged neurons are replaced by grape like cluster of vacuoles giving a sponge like appearance. So spongiform neurons are seen in prion disease but there is an exception to that.
So first of all what are the prion diseases?
They are Creutzfelt Jacob disease
Kuru
Scrapie
Mad cow disease
Gerstmann straussler scheinker syndrome and fatal familial insomnia. Among these spongiform neurons are not seen in fatal familial insomnia.