Semantic dementia (SD) is a progressive neurodegenerative disorder characterized by loss of semantic memory in both the verbal and non-verbal domains. The most common presenting symptoms are in the verbal domain however (with loss of word meaning) and it is characterized as a primary progressive aphasia.
SD patients sometimes show symptoms of surface dyslexia, a relatively selective impairment in reading low-frequency words with exceptional or atypical spelling-to-sound correspondences.
SD is one of the three canonical clinical syndromes associated with frontotemporal lobar degeneration (FTLD). SD is a clinically defined syndrome, but is associated with predominantly temporal lobe atrophy (left greater than right) and hence is sometimes called temporal variant FTLD (tvFTLD).
It was first described by Arnold Pick in 1904 but in modern times was characterised by Professor Elizabeth Warrington in 1975 but was not given the name semantic dementia until 1989. The association with temporal lobe atrophy was made by Professor John Hodges and colleagues in 1992 in a classic description of the clinical and neuropsychological features.
Read more about Semantic Dementia: Signs and Symptoms, Neuropsychology, Imaging, Pathology, Genetics, Management
Famous quotes containing the word semantic:
“Watt’s need of semantic succour was at times so great that he would set to trying names on things, and on himself, almost as a woman hats.”
—Samuel Beckett (1906–1989)