Are hallucinations and extrapyramidal signs associated with a steeper cognitive decline in degenerative dementia patients?

The aim of this study was to verify if visual hallucinations and extrapyramidal signs are associated with a high speed of cognitive decline in degenerative dementia patients with amnesic onset. The analysis of 1082 consecutive patients showed that hallucinations, but not extrapyramidal signs, were associated with a faster cognitive decline. However, patients with hallucinations were also more severe at the time of examination with the Milan Overall Dementia Assessment (MODA). One interpretation is that hallucinations are the marker of a distinct process of nervous degeneration that specifically causes a steeper cognitive decline from onset. Another interpretation is that the speed of cognitive decline is set along a continuum, and the incidence of hallucinations is simply proportional to the level of cognitive decline. The statistical analysis of our data was consistent with the latter interpretation, in that we were able to quantify the probability of presenting visual hallucinations on the basis of the overall severity of cognitive decline.