Why do DLB patients typically have visual hallucinations?
Dr. McKeith commented that the visual hallucinations of DLB seem to be a combination of attentional deficits plus visual perceptual impairments. Comparative SPECT scans of the brains of patients with AD and DLB reveal perfusion deficits to be more pronounced in the visual association cortex in DLB. Clinically, the deficit may be revealed on tests of copying and drawing. If somebody can remember the day and the date and pass on recall tests, but can t copy or draw, said Dr. McKeith, this is a good signpost that this may not be Alzheimer s disease it may be DLB. Question 2: Is DLB a rapidly progressive dementia? Initial data collected by Dr. McKeith found that a group of Alzheimer s disease patients survived 4.8 years after first clinical contact, whereas DLB patients survived for only 1.8 years (McKeith I et al. Psychol Med 1992). Rapid deterioration was therefore thought to be a characteristic of the disorder. More recent data show, however, that the natural history of cognitive declin
