A 58-year-old previously meticulous bank manager presents with 18 months of progressive personality change, behavioral disinhibition (inappropriate sexual comments, shoplifting), apathy, loss of empathy, and compulsive eating leading to 12 kg weight gain. Memory and visuospatial skills remain relatively preserved (MMSE 26/30). Examination reveals utilization behavior and palmomental reflex. T1-weighted MRI shows the pattern marked **B** in the diagram: striking asymmetric atrophy of the frontal lobes (right > left) and anterior temporal lobes (right > left), with widened sulci and narrowed 'knife-blade' gyri. The hippocampi are relatively preserved. Which of the following is the most likely diagnosis and best reflects the clinical-radiologic correlation of the structure marked **B**?
A. Behavioral variant frontotemporal dementia (bvFTD) with frontal/anterior temporal atrophy and preserved hippocampi distinguishing it from Alzheimer disease
B. Semantic dementia with left-predominant anterior temporal atrophy and preserved frontal lobes
C. Progressive supranuclear palsy with midbrain atrophy and vertical gaze palsy
D. Alzheimer disease with early hippocampal atrophy and secondary frontal involvement
Explanation
Why Behavioral variant frontotemporal dementia (bvFTD) with frontal/anterior temporal atrophy and preserved hippocampi distinguishing it from Alzheimer disease is right
The clinical presentation of personality change, behavioral disinhibition, apathy, loss of empathy, and compulsive eating combined with the radiologic signature of striking asymmetric frontal and anterior temporal atrophy (knife-blade gyri, widened sulci) with preserved hippocampi is pathognomonic for behavioral variant FTD (bvFTD). According to Rascovsky 2011 International Consensus criteria, bvFTD requires three of six core behavioral features (disinhibition, apathy, loss of empathy, compulsive/stereotyped behavior, hyperorality, and executive dysfunction), all of which are present in this case. The preserved hippocampi and relatively intact memory (MMSE 26/30) distinguish FTD from Alzheimer disease, where medial temporal atrophy is the hallmark. FTD is the second-most-common early-onset dementia after AD.
Why each distractor is wrong
Alzheimer disease with early hippocampal atrophy and secondary frontal involvement: While AD can present with behavioral changes, the preserved hippocampi and the striking frontal/anterior temporal atrophy pattern (knife-blade gyri) are incompatible with AD, where medial temporal (hippocampal) atrophy is the primary and earliest finding. The clinical syndrome of disinhibition and apathy without significant memory loss also favors FTD over AD.
Semantic dementia with left-predominant anterior temporal atrophy and preserved frontal lobes: Semantic dementia is a variant of FTD characterized by left anterior temporal atrophy with fluent but empty speech, anomia, and loss of word meaning. This patient has right-predominant atrophy and behavioral symptoms (disinhibition, apathy, compulsive eating) rather than language deficits, making behavioral variant FTD the correct diagnosis.
Progressive supranuclear palsy with midbrain atrophy and vertical gaze palsy: PSP presents with vertical supranuclear gaze palsy, axial rigidity, and the "hummingbird sign" on MRI (midbrain atrophy). This patient has no oculomotor findings and the MRI pattern is frontal/anterior temporal, not midbrain-predominant, ruling out PSP.
High-YieldNEET PG
Behavioral variant FTD = frontal/anterior temporal knife-blade atrophy + preserved hippocampi + behavioral disinhibition/apathy/loss of empathy/compulsive eating, distinguishing it from AD (hippocampal atrophy) and other dementias.
Rascovsky K, et al. Neurology. 2011;76(9):806-814. International Consensus Criteria for bvFTD.
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