Combining Neuropsychological Assessment with Neuroimaging to Distinguish Early-Stage Alzheimer's Disease from Frontotemporal Lobar Degeneration in Non-Western Tonal Native Language-Speaking Individuals Living in Taiwan: A Case Series

Neuropsychological tests (NPTs), which are routinely used in clinical practice for assessment of dementia, are also considered to be essential for differential diagnosis of Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD), especially the behavioral variants of frontotemporal dementia (bvFTD) and primary progressive aphasia (PPA) at their initial clinical presentations. However, the heterogeneous features of these diseases, which have many overlapping signs, make differentiation between AD and FTLD highly challenging. Moreover, NPTs were primarily developed in Western countries and for native speakers of non-tonal languages. Hence, there is an ongoing dispute over the validity and reliability of these tests in culturally different and typologically diverse language populations. The purpose of this case series was to examine which of the NPTs adjusted for Taiwanese society may be used to distinguish these two diseases. Since AD and FTLD have different effects on individuals' brain, we combined NPTs with neuroimaging. We found that participants diagnosed with FTLD had lower scores in NPTs assessing language or social cognition than AD participants. PPA participants also had lower measures in the Free and Cued Selective Reminding Test than those diagnosed with bvFTD, while bvFTD participants showed poorer performances in the behavioral measures than PPA participants. In addition, the initial diagnosis was supported by the standard one-year clinical follow-up.

Automated summary

Neuropsychological tests are widely used for dementia assessment in clinical practice and are also important for differentiating between Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD), especially in the initial clinical presentations of behavioral variants of frontotemporal dementia (bvFTD) and primary progressive aphasia (PPA). However, the overlapping signs and cultural differences raise concerns about the validity and reliability of these tests. This case series combined NPTs with neuroimaging to examine their effectiveness in distinguishing between AD and FTLD, and the results showed that participants diagnosed with FTLD had lower scores in language and social cognition tests compared to AD participants, while PPA participants had lower scores in the Free and Cued Selective Reminding Test compared to bvFTD participants.