Very-late-onset psychotic symptoms: psychosis or dementia? A phenomenological approach. A systematic review.

Very-late-onset psychotic symptoms (PS) are a common gateway to both neurodegenerative dementias and primary psychiatric disorders. Despite similarities in clinical expression, no consensual guidelines or a specific nosographic framework exist. The purpose of this systematic review is to establish a phenomenological classification of PS among the main neurodegenerative dementias and late psychosis. More specifically, to: 1) allow psychotic phenotypes to be considered according to aetiology; 2) help clinicians screen for psychiatric-type dementia, when appropriate; and 3) justify research into very-late-onset PS in patients with dementias at a pre-clinical cognitive stage in order to establish a nosographic framework for these PS based on the prognosis of dementia. METHODS: A literature review was conducted to search for very-late-onset PS (>60 years old) in reports of late-onset (known as primary) psychoses, Alzheimer-type dementia and Lewy body dementia, focusing on the phenomenological data. RESULTS: Very-late-onset schizophrenia-like psychosis appears to be a primary psychiatric diagnosis that is clinically distinct from PS, which emerges among established dementias, but remains a heterogeneous entity due to its age-based syndromic aspect. It is possible to differentiate between the more common phenotypes based on the aetiology of the dementia. CONCLUSION: The results confirm the value of the phenomenological approach in terms of distinguishing between different aetiologies of PS among confirmed cases of dementias. Prospective longitudinal studies are required to examine the early discriminatory characteristics of PS in order to improve prognosis based on the nosographic framework thus established.