Visual recognition memory differentiates dementia with Lewy bodies and Parkinson's disease dementia

Objective

To compare cognitive impairments in dementia with Lewy bodies (DLB) and Parkinson''s disease dementia (PDD), to discriminate between the two entities.

Methods

10 DLB and 12 PDD consecutive patients performed a neuropsychological battery designed to assess several cognitive domains: verbal and visual memory (Delayed Matching to Sample (DMS)‐48), language, gnosia, praxia and executive functions.

Results

DLB patients had poorer performances in orientation (p<0.05), Trail Making Test A (p<0.05) and reading of names of colours in the Stroop Test (p<0.05). Their scores were also lower in the visual object recognition memory test (DMS‐48), in both immediate (p<0.05) and delayed recognition (p<0.05). No differences were observed in the other tests.

Conclusion

Despite global similarities in cognitive performances between DLB and PDD patients, we observed important differences: in particular, DMS‐48, a test of visual object recognition memory and visual storage capacity, was poorer in DLB patients.Parkinson''s disease dementia (PDD) and dementia with Lewy bodies (DLB) share some common clinical features, such as extrapyramidal symptoms and neuropsychological impairment.^1,2,3 In practice, consensus guidelines recommend an arbitrary distinction between the two disorders based on a temporal sequence of 1 year between the presentation of extrapyramidal motor symptoms and the manifestation of dementia: PDD is diagnosed if dementia occurs belatedly in the context of well established Parkinson''s disease; DLB is diagnosed when motor and cognitive signs appear during the first year of evolution.⁴ A key question is whether this is a meaningful distinction between the two different clinical entities.Subtle clinical distinction in terms of cognitive pattern could prove useful for clinicians.In this study, we compared cognitive performances in a group of patients with a clinical diagnosis of “probable” DLB with those of PDD patients. As the clinical symptoms overlap, our aim was to determine possible differences in the cognitive abilities between DLB and PDD.