Prion diseases and sleep disorders

Abstract

Prion diseases (PrD) are a group of encephalopathies with neurodegenerative changes caused by prion protein (PrP) whose characteristic datum is transmissibility. In most cases they occur in a sporadic form although a group of them are familial associated with mutations in PrP gene. Phenotypic variability of fatal familial insomnia (FFI) versus familial Creutzfeldt-Jakob disease178 (fCJD178) seems to determine the different methionine⁃valine polymorphism at codon 129 of the PrP gene. Sleep disorders is one of the important clinical features for the diagnosis and definition of PrD. FFI, a hereditary disorder characterized by loss of physiological sleep with oneiric stupor, autonomic and motor hyperactivity. The polysomnography (PSG) shows disappearance of the physiological pattern of non-rapid eye movement (NREM) and rapid eye movement (REM) sleep, as well as sleep spindles and K-complexes were absent. The hypothesis of the origin of these disorders is thalamic neuronal loss, especially in the anterior and dorsomedial nuclei, described in the neuropathology of these patients; besides, PET reveals hypofunction of thalamic nuclei, centres responsible for controlling wake-sleep. In CJD the wake-sleep disorders is not considered characteristic; nonetheless, frequent alterations have been found in the electroencephalographic registers of sleep. Besides thalamic neurodegeneration, there could be common etiopathogenic mechanisms in PrD in relation to the biological function of PrP.