Clinical Features of Late-onset Semantic Dementia.

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.

Repetitive Behaviors in Frontotemporal Dementia: Compulsions or Impulsions?

OBJECTIVE: The presence of repetitive behaviors is one of the core criteria for behavioral variant frontotemporal dementia (bvFTD). Patients with bvFTD often have perseverative, stereotyped, or compulsive-ritualistic behavior as an early aspect of their disorder. It is unclear whether such behaviors are related to compulsions, as in obsessive-compulsive disorder (OCD), or are part of the impulse disorder spectrum. METHODS: The authors investigated early (within 3 years) repetitive behaviors among 93 well-characterized patients who met International Consensus Criteria for clinically probable bvFTD and compared the results with the literature on OCD. The most common repetitive behaviors among 59 (63.4%) bvFTD patients were stereotypies of speech (35.5%), simple repetitive movements (15.2%-18.6%), hoarding and collecting (16.9%), and excessive or unnecessary trips to the bathroom (13.5%). RESULTS: Only hoarding and collecting was significantly common in both bvFTD and OCD; otherwise, the bvFTD patients had very low frequencies of the common OCD behaviors of checking, cleaning, counting, and ordering. The repetitive behaviors in bvFTD were not associated with verbalized anxiety, obsessional ideation, or reports of relief after completing the act. In contrast, these behaviors were often triggered by environmental stimuli and could be temporarily prevented from completion without undue distress. Finally, among the bvFTD patients, the repetitive behaviors were always associated with impulsive or disinhibited behaviors, such as inappropriate verbal or physical behavior. CONCLUSIONS: These findings suggest that the repetitive behaviors in bvFTD are repetitive impulsions, possibly from specific involvement of frontostriatal-anterior temporal pathology.

The Progressive Acalculia Presentation of Parietal Variant Alzheimer's Disease.

BACKGROUND: Many patients with early-onset Alzheimer's disease (EOAD; age of onset <65 years) have non-amnestic presentations involving language (logopenic primary progressive aphasia, lvPPA), visuospatial abilities (posterior cortical atrophy, PCA), and even asymmetric symptoms consistent with corticobasal syndrome (CBS). An inferior parietal lobule variant of EOAD commonly presents with progressive difficulty with calculations. METHODS: We reviewed 276 EOAD patients for presentations with predominant acalculia. These patients were diagnosed with clinically probable Alzheimer's disease (AD) verified by positron emission tomography (PET) or cerebrospinal fluid amyloid-ß or tau biomarkers. RESULTS: We identified 18 (9M/9F) (6.5%) EOAD patients with progressive acalculia that did not meet most criteria for lvPPA, visual PCA, or CBS. Their ages of onset and presentation were 56.6 (5.0) and 59.4 (6.5), respectively. Their acalculia was consistent with a primary acalculia ("anarithmetia") not explained by language or visuospatial impairments. Many also had anomia (14/18), ideomotor apraxia (13/18), and the complete Gerstmann's syndrome (7/18). Visual analysis of their diverse magnetic resonance imaging disclosed biparietal atrophy, disproportionately worse on the left. CONCLUSIONS: Primary acalculia may be the most common manifestation of an inferior parietal presentation of EOAD affecting the left intraparietal sulcus. This parietal variant also commonly involves progressive anomia, ideomotor apraxia, and other elements of Gerstmann's syndrome. The early recognition of patients with this variant, which is distinguishable from lvPPA, visual PCA, or CBS, would be facilitated by its recognition as a unique subtype of EOAD.