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KMID : 1100220050040010010
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Dementia and Neurocognitive Disorders
2005 Volume.4 No. 1 p.10 ~ p.13
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Semantic Dementia
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Kim Eun-Joo
Ku Bon-D.
Na Duk-Lyul
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Abstract
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Semantic dementia (SD) is a temporal variant of frontotemporal lobar degeneration (FTLD) characterized by a progressive loss of conceptual knowledge with relative sparing of cognitive functions such as episodic memory, nonverbal problem solving, and visuospatial skills. Anterior temporal areas are primarily involved and this involvement usually has hemispheric asymmetry. When left temporal lobe is predominatly affected (left SD), semantic memory for words (especially noun) is lost, resulting in anomia and auditory comprehension deficit. In contrast, patients with ‘right SD’ present with difficulty recognizing familiar faces. As the disease progresses, anomia and prosopagnosia evolve into transcortical/Wernicke’s aphasia and visual agnosia for objects, leading to behavioral changes associated with frontal and temporal degeneration and global dementia. MRI shows asymmetric atrophy in the left or right temporal lobes, particulary marked in the anterior temporal poles. Relative preservation of episodic memory despite the atrophy of the medial and temporal lobe including the hippocampus in SD is one of the issues discussed currently. The underlying pathology of SD is microvacuolar degeneration and astrocytosis of the involved cortical area, sharing features with other types of FTLD.
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KEYWORD
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Semantic dementia (SD), Frontotemporal lobar degeneration (FTLD)
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