Abstract
Semantic dementia is a lobar atrophy syndrome, related to a degeneration of anterior temporal regions, and characterized by a very predominant impairment of semantic memory. Whereas the diagnosis is relatively easy to establish in the typical form and if the patient is seen early, the emergence of possible additional cognitive or psycho-behavioural disorders can lead to a misdiagnosis in favour of a frontotemporal dementia syndrome or even probable Alzheimer's disease.