Most of the time, the patient does not spontaneously report hallucinations and only a small portion of them are detected by the spouse (emerged part of the "iceberg"). Patients should be specifically questioned on the presence of minor, visual, and auditory hallucinations. As reported by Fenelon and colleagues, (15) the most frequent type are visual hallucinations. The patient has a vivid sensation of the presence of somebody either somewhere in the room or, less often, behind him or her. The presence is often a relative (alive or deceased) who is often perceived as benevolent like a "guardian angel." However, the patient is ready to accept that the "presence" is not real.
Formed visual hallucinations are more complex with vivid scenes "like a film," sometimes close to real (members of family), sometimes full of fantasy (ninja turtles, dancing Russians, medieval stories), but soundless. In some cases, the hallucinations may be frightening (house burning, wild animals). Auditory hallucinations are rare and tactile hallucinations often involve animals. As they are more frequent in the evening they may be associated with vivid dreams and sleep disorders (15).
In all cases, the main risk factor for hallucinations is cognitive impairment. Therefore, it is important to detect them as they are among features used for the diagnostic criteria of dementia with Lewy bodies (DLB) in addition to cognitive impairment, attentional and visuospatial deficits, fluctuating cognition, and parkinsonism (16).
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