The neuropsychiatric examination of the young-onset dementias.

Young-onset dementias frequently present with prominent behavioral features and constitute a diagnostic challenge. Most cases are secondary to neurodegenerative conditions, including the behavioral variant of frontotemporal dementia, which has overlapping symptoms with many primary psychiatric disorders. This article reviews the differential diagnosis and neuropsychiatric assessment of young-onset dementia, which includes detailed history taking, family history, mental status examination, office-based cognitive tests, and a focused neurologic examination. The clinical examination serves to establish the presence of a dementia and the specific clinical syndrome. Biomarkers can be subsequently integrated in a probabilistic model to determine the most likely neuropathological process.