Cerebral correlates of psychotic syndromes in neurodegenerative diseases

Abstract

Psychosis has been recognized as a common feature in neurodegenerative diseases and a core feature of dementia that worsens most clinical courses. It includes hallucinations, delusions including paranoia, aggressive behaviour, apathy and other psychotic phenomena that occur in a wide range of degenerative disorders including Alzheimer's disease, synucleinopathies (Parkinson's disease, dementia with Lewy bodies), Huntington's disease, frontotemporal degenerations, motoneuron and prion diseases. Many of these psychiatric manifestations may be early expressions of cognitive impairment, but often there is a dissociation between psychotic/behavioural symptoms and the rather linear decline in cognitive function, suggesting independent pathophysiological mechanisms. Strictly neuropathological explanations are likely to be insufficient to explain them, and a large group of heterogeneous factors (environmental, neurochemical changes, genetic factors, etc.) may influence their pathogenesis. Clinico-pathological evaluation of behavioural and psychotic symptoms (PS) in the setting of neurodegenerative and dementing disorders presents a significant challenge for modern neurosciences. Recognition and understanding of these manifestations may lead to the development of more effective preventive and therapeutic options that can serve to delay long-term progression of these devastating disorders and improve the patients' quality of life. A better understanding of the pathophysiology and distinctive pathological features underlying the development of PS in neurodegenerative diseases may provide important insights into psychotic processes in general.

Fig 1

scheme of the interplay of neurochemical and neuropathological factors in the pathogenesis of AD and its neuropsychiatric disorders.

Fig 2

Diagram of the major visual pathways implicated pathologically in VH in PD.

Fig 3

Circuiting interconnections between psychotic and cognitive functions. GPE: external globus pallidus; STN: subthalamic nucleus; VP: ventral pallidum; GPi-SNpr: internal globus pallidus and substantia nigra pars reticulata; DA: dopamine. Modified from Barone P, Santangelo G. Interaction between affect and executive functions in Parkinson’s disease. In: Emre M, editor. Cognitive Impairment and Dementia in Parkinson’s Disease. Oxford, UK: Oxford University Press; 2010. pp. 65–73.