Neurobiology of sleep disturbances in neurodegenerative disorders.

This review presents sleep disturbances and their underlying pathophysiology in three categories of neurodegenerative disorders namely tauopathies, synucleinopathies, and Huntington's disease (HD) and prion-related diseases. Sleep abnormalities are a major and early feature of neurodegenerative disorders, especially for synucleinopathies, HD and prion-related diseases, in which the sleep-related brainstem regions are severely altered and impaired sooner than in most of the tauopathies. In synucleinopathies, HD and prion-related diseases, specific sleep disturbances, different from those observed in tauopathies, are considered as core manifestations of the disease and in some cases, as preclinical signs. For this reason, the evaluation of sleep components in these neurodegenerative disorders may be useful to make a diagnosis and to assess the efficacy of pharmacotherapy. Since sleep disruption may occur early in the course of neurodegeneration, sleep disturbance may serve as groundwork to study the efficacy of neuroprotective agents to prevent or delay the development of a full-blown neurodegenerative disorder. The cause of sleep disturbances in neurodegenerative disorders may be attributed to several factors, including age-related modifications, symptoms of the disease, comorbid conditions and the neurodegenerative process itself.