Semantic dementia

Main articles: Aphasia and Primary progressive aphasia
Semantic dementia
Other namessemantic variant primary progressive aphasia
SpecialtyNeurology

In neurology, semantic dementia (SD), also known as semantic variant primary progressive aphasia (svPPA), is a progressive neurodegenerative disorder characterized by loss of semantic memory in both the verbal and non-verbal domains. However, the most common presenting symptoms are in the verbal domain (with loss of word meaning).[1][2][3] Semantic dementia is a disorder of semantic memory that causes patients to lose the ability to match words or images to their meanings.[4] However, it is fairly rare for patients with semantic dementia to develop category specific impairments, though there have been documented cases of it occurring.[5] Typically, a more generalized semantic impairment results from dimmed semantic representations in the brain.[6]

SD is one of the three canonical clinical syndromes associated with frontotemporal lobar degeneration (FTLD), with the other two being frontotemporal dementia and progressive nonfluent aphasia. 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).[7] SD is one of the three variants of primary progressive aphasia (PPA), which results from neurodegenerative disorders such as FTLD or Alzheimer's disease. There are distinctions between Alzheimer's disease and semantic dementia with regard to types of memory affected.[citation needed] In general, Alzheimer's disease is referred to as a disorder affecting mainly episodic memory, defined as the memory related to specific, personal events distinct for each individual. Semantic dementia generally affects semantic memory, which refers to long-term memory that deals with common knowledge and facts.

SD was first described by Arnold Pick in 1904 and in modern times was characterized by Professor Elizabeth Warrington in 1975,[8] but it was not given the name semantic dementia until 1989.[9] The clinical and neuropsychological features, and their association with temporal lobe atrophy were described by Professor John Hodges and colleagues in 1992.[10]

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  2. ^ Bonner, M.F.; Ash, S.; Grossman, M. (November 2010). "The new classification of primary progressive aphasia into semantic, logopenic, or nonfluent/agrammatic variants". Curr Neurol Neurosci Rep. 10 (6): 484–90. doi:10.1007/s11910-010-0140-4. PMC 2963791. PMID 20809401.
  3. ^ Harciarek, M.; Kertesz, A. (September 2011). "Primary progressive aphasias and their contribution to the contemporary knowledge about the brain-language relationship". Neuropsychol Rev. 21 (3): 271–87. doi:10.1007/s11065-011-9175-9. PMC 3158975. PMID 21809067.
  4. ^ "Alzheimer Europe - Dementia - Other forms of dementia - Neurodegenerative diseases - Fronto-Temporal Degeneration - Semantic Dementia (SD)". www.alzheimer-europe.org. Retrieved 2020-07-18.
  5. ^ "Encephalitis, Herpes Simplex". NORD (National Organization for Rare Disorders). Retrieved 2020-07-19.
  6. ^ Lambon Ralph, M. A.; Lowe, C.; Rogers, T. T. (2006-11-21). "Neural basis of category-specific semantic deficits for living things: evidence from semantic dementia, HSVE and a neural network model". Brain. 130 (4): 1127–1137. doi:10.1093/brain/awm025. ISSN 0006-8950. PMID 17438021.
  7. ^ Weder ND, Aziz R, Wilkins K, Tampi RR (2007). "Frontotemporal dementias: a review". Ann Gen Psychiatry. 6: 15. doi:10.1186/1744-859X-6-15. PMC 1906781. PMID 17565679.
  8. ^ Warrington, E.K. (November 1975). "The selective impairment of semantic memory". Q J Exp Psychol. 27 (4): 635–57. doi:10.1080/14640747508400525. PMID 1197619. S2CID 2178636.
  9. ^ Snowden, J.S.; Goulding, P.J.; Neary, D. (1989). "Semantic dementia: a form of circumscribed cerebral atrophy". Behav Neurol. 2 (3): 167–82. doi:10.1155/1989/124043.
  10. ^ Hodges, J.R.; Patterson, K.; Oxbury, S.; Funnell, E. (December 1992). "Semantic dementia. Progressive fluent aphasia with temporal lobe atrophy". Brain. 115 (Pt 6): 1783–806. doi:10.1093/brain/115.6.1783. PMID 1486461.