Apraxia profiles—A single cognitive marker to discriminate all variants of frontotemporal lobar degeneration and Alzheimer's disease

Abstract Introduction Apraxia is common in neurodegenerative dementias but underrepresented in clinical workup for differential diagnoses. Methods Praxis‐profiles were assessed with the Dementia Apraxia Test in 93 patients with early stages of biologically supported Alzheimer's disease or frontotemporal lobar degeneration: semantic primary‐progressive aphasia, nonfluent primary‐progressive aphasia, and behavioral variant frontotemporal dementia. Associations with core cognitive deficits of the dementia subtypes (i.e., visuospatial, sociocognitive, and semantic‐linguistic) were explored. Results Patients showed significant apraxia compared with healthy controls but also disease‐specific praxis‐profiles. Using only the Dementia Apraxia Test, all four dementia subtypes could be correctly discriminated in 64.4% of cases, and in 78.2% when only distinguishing Alzheimer's disease versus frontotemporal lobar degeneration. Praxis‐profiles showed consistent associations with core cognitive impairments of the different dementia subtypes. Discussion The Dementia Apraxia Test is a valid, time‐efficient and versatile cognitive marker to delineate variants of frontotemporal lobar degeneration and Alzheimer's disease in clinical routine, facilitating differential diagnoses of dementia subtypes in early disease stages.