Neuro-ophthalmological aspects of prion diseases

Abstract

Prion brain diseases (Kuru, Creutzfeldt-Jakob disease, familial fatal insomnia (FFI), Gerstman-Straussler-Scheinker syndrome) are conditioned by the host’s genome. Susceptibility (hereditary) is related to the PrPc gene polymorphism (insertion and/or point mutations at different codons). The normal harmless PrPc (neuron) is transformed into a rogue structurally altered PrPsc (scrapie) invading neurocells. Human consumption of protein from bovine spongiform encephalopathy (BSE) cattle, fed scrapie-sheep offal, may be responsible for prion disease. The clinical features are mirrored by a wide spectrum of brain grey matter involvement in middle-aged patients. Progressive dementia and supranuclear (ocular) motor symptoms are characteristic; at onset visual symptoms may occur in 20–25% of cases. In dementing patients, diagnosis of prion disease may only be confirmed by brain biopsy, demonstrating the typical spongiosis and pleated prion plaques (methacarn fixation). Care should be taken to never use tissue from dementing patients for substitutive therapy or transplants.