Alzheimer's Disease or Behavioral Variant Frontotemporal Dementia? Review of Key Points Toward an Accurate Clinical and Neuropsychological Diagnosis

Abstract

Alzheimer's disease (AD) and frontotemporal dementia (FTD) are the most common neurodegenerative early-onset dementias. Despite the fact that both conditions have a very distinctive clinical pattern, they present with an overlap in their cognitive and behavioral features that may lead to misdiagnosis or delay in diagnosis. The current review intends to summarize briefly the main differences at the clinical, neuropsychological, and behavioral levels, in an attempt to suggest which aspects would facilitate an adequate diagnosis in a clinical setting, especially in Latin American and low- and middle-income countries, where the resources needed for a differential diagnosis (such as MRI or biomarkers) are not always available. A timely diagnosis of AD and FTD have significant implications for the medical management and quality of life of patients and careers.

Keywords: Alzheimer’s disease; differential diagnosis; frontotemporal dementia; neuropsychology; young onset dementia.

Fig. 1.

Neuropsychological and clinical signatures of tAD, bdAD, and bvFTD. Each point of the target shows a particular cognitive or clinical domain. The distance along the radial dimension indicates the level of impaired or decline function. Loss of function is indicated by a major distance from the central point, which corresponds to the cognitive/clinical domain in reference. The neuropsychological profile of a particular disease is evident in the pattern of decline of cognitive and clinical features: the differential loss of function across cognitive domains.

Fig. 2.

Summary of the recommended key points to be assessed in each stage of the clinical examination.

Fig. 3.

Patterns of brain atrophy in bvFTD, bdAD, and tAD. Image modified from Elahi and Miller, 2017 [14]. The brain images show patterns of atrophy on structural neuroimaging observed across the different clinical syndromes. In bvFTD, the main atrophy is localized into right frontal structures. In the bdAD, voxel-based morphometric studies reveal temporoparietal atrophy with relative preservation of frontal grey matter. In tAD atrophy is first noted in the medial temporal lobes and gradually spreads toward broader temporoparietal and posterior cingulate cortices.