Differential diagnosis in the memory clinic: Exploring the value of improved neuropsychological examination

The objective of this thesis was to 1) expand the research on the employability of symptom validity tests (SVTs) in memory clinic populations, and 2) examine brain-behavior relationships as a function of credible and non-credible performance. In the first place it can be concluded that non-credible cognitive test performance occurs in a non- negligible proportion of memory clinic patients, which, if undetected, will result in invalid MCI diagnoses. Furthermore, our findings showed that, in patients exerting non-credible performance, there is virtually no association between hippocampal volumes and memory performance and that this group did not show cognitive decline after two years. Our second main conclusion was that brain atrophy in (medial) temporal lobe areas explains most of the variance in cognitive decline, especially memory dysfunction. Therefore, relations between non-memory cognitive domains and brain atrophy in other structures than the temporal lobe are probably overshadowed by memory decline and temporal lobe atrophy, especially in early stages of the disease. In general, the results of our research have shown that brain-behavior relations may be obscured and the diagnosis of a preclinical dementia stage may be invalid in patients who do not perform to the best of their ability during cognitive evaluation. This underscores the importance of administering formal tests of symptom validity in the examination of patients who present with cognitive complaints that may signify an early stage of dementia, especially when patients are below 65 years of age