Two distinct amnesic profiles in behavioral variant frontotemporal dementia

Background: Whether or not episodic memory deficit is a characteristic of behavioral variant frontotemporal dementia (bvFTD) is a crucial question for its diagnosis and management.

Methods: We compared the episodic memory performance profile of bvFTD patients with healthy control subjects and patients with Alzheimer's disease (AD) as defined by clinical and biological criteria. Episodic memory was assessed with the Free and Cued Selective Reminding Test, which controls for effective encoding and identifies memory storage ability resulting from consolidation processing. One hundred thirty-four participants were evaluated: 56 patients with typical clinical presentation of AD and pathophysiological evidence as defined by cerebrospinal fluid AD biomarker profile and/or significant amyloid retention on Pittsburgh Compound B positron emission tomography; 56 patients diagnosed with bvFTD with no evidence of AD-cerebrospinal fluid biomarkers when a profile was available (28/56), including 44 progressive (bvFTD) and 12 nonprogressive (phenocopies) patients; and 22 control subjects with negative amyloid imaging.

Results: Memory scores could not differentiate bvFTD from AD patients (sensitivity and specificity <50%). Taking into account the individual distribution of Free and Cued Selective Reminding Test scores, half of bvFTD patients had a deficit of free recall, total (free + cued) recall, and delayed recall as severe as AD patients. The other half had subnormal scores similar to phenocopies and a delayed recall score similar to control subjects.

Conclusions: We observed two distinct amnesic profiles in bvFTD patients that could reflect two types of hippocampal structure and Papez circuit involvement. These findings on episodic memory profiles could contribute to discussions on the recent international consensus criteria for bvFTD.