The Behavioral/Dysexecutive Variant of Alzheimer’s Disease: A Case Series with Clinical, Neuropsychological, and FDG-PET Characterization
Bibliographic record
Abstract
INTRODUCTION: It is well known that some patients with Alz-heimer's disease (AD) have atypical, nonamnestic presentations. While logopenic aphasia and posterior cortical atrophy are well-characterized atypical variants of AD, the behavioral/dysexecutive variant remains a controversial entity, lacking consensus regarding its distinctive clinical and imaging features. METHODS: We present a case series of 8 patients with biomarker confirmation of AD (cerebrospinal fluid [CSF] analysis or amyloid positron emission tomography [PET]) and a progressive frontal syndrome, defined as prominent behavioral and/or executive deficits at initial presentation. We characterize the cohort based on clinical features, cognitive performance in 4 domains (memory, visuospatial, executive, and language) as well as behavior on the Dépistage Cognitif de Québec (DCQ), and regional brain metabolism using 18F-fluorodeoxyglucose PET (FDG-PET). We compare these features with 8 age-matched patients diagnosed with the behavioral variant of frontotemporal dementia (bvFTD) and 37 patients with typical amnestic AD. RESULTS: Patients with the behavioral/dysexecutive variant of AD presented with early-onset (mean age: 59 years old) progressive executive and behavioral problems reminiscent of bvFTD, including disinhibition, loss of social conventions, and hyperorality. Patients scored higher on the Memory Index and lower on the Behavioral Index than patients with amnestic AD on the DCQ, yet they were indistinguishable from patients with bvFTD on each of the cognitive indices. Visual analysis of FDG-PET revealed half of patients with behavioral/dysexecutive AD presented with frontal hypometabolism suggestive of bvFTD and only 3/8 (37.5%) presented significant hypometabolism of the posterior cingulate cortex. Group-level analysis of FDG-PET data revealed that the most hypometabolic regions were the middle temporal, inferior temporal, and angular gyri in behavioral/dysexecutive AD and the inferior frontal gyrus, anterior cingulate cortex, caudate nucleus, and insula in bvFTD. CONCLUSION: The behavioral/dysexecutive variant of AD is a rare, atypical young-onset variant of AD defined clinically by early and prominent impairments in executive and behavioral domains. While behavioral/dysexecutive AD is hardly distinguishable from bvFTD using clinical and cognitive features alone, CSF biomarkers and temporoparietal hypometabolism help predict underlying pathology during life.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.002 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.003 | 0.001 |
| Science and technology studies | 0.002 | 0.002 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".