Chapter

Hallucinations in the context of dementing illnesses

Urs Peter Mosimann and Daniel Collerton

in Hallucinations

Published on behalf of Oxford University Press

Published in print June 2010 | ISBN: 9780199548590
Published online February 2013 | e-ISBN: 9780191754623 | DOI: http://dx.doi.org/10.1093/med/9780199548590.003.0017
Hallucinations in the context of dementing illnesses

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In this chapter, we will review the current epidemiological, clinical, and biological evidence on the relationships between hallucinations and dementing illnesses, particularly Lewy Body Dementia (LBD) and Parkinson's disease dementia (PDD) where visual hallucinations are common (see also Fénelon, this volume). We will compare dementia-specific models for their genesis with models derived in other disorders. We will then evaluate assessment, treatment, and support options, and finally, look to unresolved issues and the potential for further developments.

Dementia can be neatly defined as an acquired, generally progressive global impairment of cognition in the absence of impaired consciousness. As with all neat definitions, its simplicity is clinically useful but may also be misleading. In most cases, impairments are not equal in all cognitive areas (the exact nature of cognitive change varies by the stage and type of dementing illness), and consciousness may be variably affected. The focus on cognition alone distracts attention from the non-cognitive effects of dementia—emotional, behavioural, psychological, and psychiatric—including hallucinations. There is only a difference of degree between cognitive impairments which are, or are not, severe enough to be classed as dementia. It may be more helpful to think of a dementing process, rather than a state of dementia. The reader with a special interest in the assessment and management of dementia may find more detailed information in specific textbooks or in up-to-date assessment guidelines, for example, the European Federation of Neurological Societies Guidelines (Waldemar et al., 2007).

The overall prevalence of dementia in Western Europe is about 5.4% for those over the age of 60 years, and the estimated annual incidence is 8.8 per 1,000 inhabitants. The prevalence increases exponentially with age: 1% (60–64 years), 1.5 % (65–69 years), 3.6% (70–74 years), 6% (75–79 years), 12.2% (80–84 years), and 24.8% (85 years). Global prevalence rates will double in the next 20 years, mainly due to an increased life expectancy in the third world (Ferri et al., 2005). The economical cost of dementia in Europe exceeds 55 billion Euros per year with the major costs emerging in institutional care (Johnson et al., 2005). If the unpaid work of family and other carers is included, the costs rise threefold.

Chapter.  11802 words.  Illustrated.

Subjects: Psychiatry

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