title: What is semantic dementia?: a cohort study of diagnostic features and clinical boundaries.
abstract: OBJECTIVE
  To describe a large, clinically defined cohort of patients with semantic dementia (SD) that highlights important, sometimes overlooked features and to compare it with similar entities.
  
  
  METHODS
  Cohort study.
  
  
  METHODS
  A cognitive neurology clinic.
  
  
  METHODS
  A population of 48 patients clinically diagnosed with SD was contrasted with 52 patients with progressive nonfluent aphasia, 42 patients with a behavioral variety of frontotemporal dementia, and 105 patients with Alzheimer disease on speech output characteristics, comprehension, naming, and repetition subtests of the Western Aphasia Battery, the Frontal Behavioral Inventory, and other cognitive tests. Neuroimaging was visually analyzed, and 6 patients with SD had autopsy.
  
  
  RESULTS
  Of 37 patients with probable SD, 48.6% had semantic jargon; 21.6%, excessive garrulous output; and 75.7%, some pragmatic disturbance. Semantic substitutions were frequent in SD (54.1%) but phonological errors were absent, in contrast to progressive nonfluent aphasia with the opposite pattern. All but 3 patients with probable SD questioned the meaning of words. Patients with SD had significantly lower naming and comprehension scores, and their fluency was between progressive nonfluent aphasia and Alzheimer disease or behavioral frontotemporal dementia. Behavior was abnormal in 94.6% of patients with probable SD.
  
  
  CONCLUSIONS
  Semantic dementia is distinguishable from other presentations of frontotemporal dementia and Alzheimer disease, not only by fluent speech and impaired comprehension without loss of episodic memory, syntax, and phonology but also by empty, garrulous speech with thematic perseverations, semantic paraphasias, and poor category fluency. Questioning the meaning of words (eg, "What is steak?") is an important diagnostic clue not seen in other groups, and behavior change is prevalent.
authors.affiliation: Department of Clinical Neurological Sciences, University of Western Ontario, 268 Grosvenor St, London, ON N6A 4V2. andrew.kertesz@sjhc.london.on.ca
authors.forename: Andrew
authors.initials: A
authors.lastname: Kertesz
authors.forename: Sarah
authors.initials: S
authors.lastname: Jesso
authors.forename: Michal
authors.initials: M
authors.lastname: Harciarek
authors.forename: Mervin
authors.initials: M
authors.lastname: Blair
authors.forename: Paul
authors.initials: P
authors.lastname: McMonagle
mesh_terms: D000328:Adult; D000368:Aged; D000544:Alzheimer Disease / Q000175:diagnosis / Q000473:pathology / Q000503:physiopathology; D001037:Aphasia / Q000175:diagnosis / Q000473:pathology / Q000503:physiopathology; D015415:Biomarkers; D001921:Brain / Q000473:pathology / Q000503:physiopathology; D015331:Cohort Studies; D003937:Diagnosis, Differential; D003952:Diagnostic Imaging; D005260:Female; D057180:Frontotemporal Dementia / Q000175:diagnosis / Q000473:pathology / Q000503:physiopathology; D057174:Frontotemporal Lobar Degeneration / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology*; D006801:Humans; D007802:Language; D007806:Language Disorders / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology*; D007807:Language Tests; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D012660:Semantics; D013060:Speech / Q000502:physiology
chemical_list: D015415:Biomarkers