Clinical Manifestations and Neural Basis of Semantic Dementia: Converging Evidences From Brain Imaging Studies

Semantic dementia (SD) is a progressive neurodegenerative disorder primarily characterized by core linguistic deficits, notably impaired confrontation naming and single-word comprehension. Associated features include surface dyslexia, prosopagnosia, relatively preserved speech production, and emotional or behavioral abnormalities. Neuroimaging reveals initial asymmetrical atrophy of the anterior temporal pole, with subsequent progression posteriorly and contralaterally. Early detection is challenging due to initial presentation often manifesting as mild word-finding difficulties, furthermore, comorbid behavioral-emotional symptoms and distinct clinical profiles associated with right- versus left-sided atrophy complicate diagnosis. Therefore, this paper comprehensively delineates the principal clinical features of SD, encompassing language deficits, emotional impairment, behavioral disturbances, and other domains. It also reviews structural and functional imaging findings and investigates the relationship between clinical manifestations and patterns of brain injury. To advance understanding of SD's clinical manifestation, the paper introduces the controlled semantic and social-semantic frameworks.