Background: The anterior part of the insula appears atrophied in the early stage of dementia with Lewy bodies (DLB) whereas it is not the case in early Alzheimer's disease (AD).
Objective: The objective of this study was to develop neuropsychological markers supposed to reflect insular dysfunction, which would facilitate early diagnosis of DLB, namely in comparison to AD.
Methods: Twelve patients with DLB, 12 patients with AD, all at the stage of Mild cognitive impairment (MCI) or mild dementia, as well as 10 Controls subjects (CS) participated in the study. Cognitive functions supposedly related to the insula were evaluated with a battery of tests: a facial expression recognition test, a test assessing the feeling of disgust with images, a test evaluating idioms' comprehension, an empathy questionnaire and a questionnaire screening for disgusting behaviors.
Results: Compared to AD patients and CS, DLB patients experienced less disgust when they were shown disgusting images, whereas their ability to recognize emotional expression of disgust appeared to be preserved. Furthermore, DLB patients seemed less empathetic than AD patients. Finally, compared to CS, DLB patients were less effective to provide an intuitive decision about idioms' signification since they needed significantly more time to answer.
Conclusion: This preliminary study suggests the existence of a potential « insular cognitive impairment » profile in DLB at the early stage. These results provide interesting leads to develop tools facilitating the differential diagnosis of DLB and AD.
Keywords: Alzheimer's disease; dementia with Lewy bodies; insula; mild cognitive impairment.