Clinical Features of Late-onset Semantic Dementia

Abstract

Background: Semantic dementia (SD) is characterized by progressive semantic anomia extending to a multimodal loss of semantic knowledge. Although often considered an early-onset dementia, SD also occurs in later life, when it may be misdiagnosed as Alzheimer disease (AD). Objective: To evaluate late-onset SD in comparison to early-onset SD and to AD. Methods: We identified 74 individuals with SD and then compared those with late-onset SD (≥65 years of age) to those with early-onset SD (<65) on demographic and clinical features. We also compared a subgroup of 23 of the late-onset SD individuals with an equal number of individuals with clinically probable AD. Results: Twenty-six (35.1%) of the SD individuals were late onset, and 48 (64.9%) were early onset. There were no differences between the two groups on clinical measures, although greater asymmetry of temporal involvement trended to significance in the late-onset SD group. Compared to the 23 AD individuals, the subgroup of 23 late-onset SD individuals had worse performance on confrontational naming, irregular word reading, and face recognition; however, this subgroup displayed better verbal delayed recall and constructions. The late-onset SD individuals also experienced early personality changes at a time when most individuals with AD had not yet developed behavioral changes. Conclusions: Approximately one-third of SD individuals may be late onset, and the differentiation of late-onset SD from AD can lead to better disease management, education, and prognosis. SD may be distinguished by screening for disproportionate changes in reading, face recognition, and personality.

Clinicopathological diversity of semantic dementia: Comparisons of patients with early‐onset versus late‐onset, left‐sided versus right‐sided temporal atrophy, and TDP‐type A versus type C pathology

“…In a review of 49 patients with right temporal atrophy, only two (4%) patients had TDP‐type pathology 10 . Most neuropathological studies of SD have targeted early‐onset cases, and investigations on late‐onset cases are lacking, despite the fact that 35–46% of SD patients are late onset 12,13 . In this study, regardless of the side of predominant atrophy, age at onset appeared to be an important factor in determining the TDP pathology subtype.…”

“…10 Most neuropathological studies of SD have targeted earlyonset cases, and investigations on late-onset cases are lacking, despite the fact that 35-46% of SD patients are late onset. 12,13 In this study, regardless of the side of predominant atrophy, age at onset appeared to be an important factor in determining the TDP pathology subtype. TDP type-A pathology has been associated with behavioral variants of FTD or non-fluent variants of PPA, but it can also be associated with SD.…”

“…Although SD typically develops before the age of 65 (early onset), it occurs after the age of 65 (late onset) in approximately 46% of individuals with SD 12 . Late‐onset SD is often misdiagnosed as AD 13 . However, amyloid positron emission tomography (PET) studies of frontotemporal dementia (FTD), including SD, indicate a considerable proportion of amyloid positivity 14,15 , suggesting that misdiagnosis and comorbid AD pathology increases with age.…”

“…12 Late-onset SD is often misdiagnosed as AD. 13 However, amyloid positron emission tomography (PET) studies of frontotemporal dementia (FTD), including SD, indicate a considerable proportion of amyloid positivity 14,15 , suggesting that misdiagnosis and comorbid AD pathology increases with age. Recently, it has become common for AD to combine TDP-43 pathology, accelerating the severity of dementia with impaired naming and medial temporal atrophy on magnetic resonance imaging (MRI).…”

Distinguishing Semantic Variant Primary Progressive Aphasia from Alzheimer’s Disease

“…Clinicians need to consider svPPA in the differential diagnosis of AD and other dementias (Table 1) [1]. In comparison to AD, svPPA patients have more prominent difficulties on confrontational naming, irregular word reading, and face recognition, and better episodic memory and visuospatial skills [34]. The presence of some hippocampal atrophy in svPPA may challenge the specificity of hippocampal atrophy for AD; however, studies suggest that svPPA primarily involves the anterior hippocampus and a functional semantic memory network and spares the more posterior hippocampus affected by AD [35][36][37].…”