Slow wave and rem sleep mechanisms are differently altered in hereditary pick disease associated with the TAU G389R mutation.

Abstract

Sleep disturbances are found in the course of most dementing syndromes. We report a longitudinal polysomnographic and 18FDG-PET study in a 38-year-old male with FTDP17 carrying the Tau gene mutation G389R. All-night sleep EEG and wake cerebral glucose metabolism at rest (eyes/ears covered) of the preceding day were studied twice, eight months (Night 1; PET 1) and sixteen months (Night 2; PET 2) after the initial neurological evaluation. The Night 1 study showed sleep fragmentation associated to a short REM latency and a severe reduction of slow wave sleep, with relatively preserved NREM-REM sleep cycles; daytime PET 1 revealed severe cerebral glucose metabolic reductions in frontal and temporal areas, with relative preservation of remaining cortical regions and subcortical structures. On Night 2, the total sleep time was less than 5 hours, delta sleep and REM latency remained shortened and only two sleep cycles could be identified; daytime PET 2 exam revealed a greater cortical metabolic impairment and an involvement of subcortical brain regions as compared to PET 1. Post-mortem neuropathological data showed severe neuronal loss, spongiosis and gliosis that were mostly marked in cortical layers I, II, V and VI. In vivo, neurometabolic and post-mortem neuropathological data are consistent with and indicative of a severe dysfunction of intra- and trans-hemispheric regional connectivity and of cortico-thalamic circuits. These findings suggest that the decreased cortical and subcortical connectivity may have been the main pathophysiological mechanism responsible for delta sleep reduction and the cognitive decline.