How preserved is episodic memory in behavioral variant frontotemporal dementia?

Abstract

Objective: Studies have shown variable memory performance in patients with behavioral variant frontotemporal dementia (bvFTD). Our study investigated whether this variability is due to the admixture of patients with true bvFTD and phenocopy patients. We also sought to compare performance of patients with bvFTD and patients with Alzheimer disease (AD). Methods:We analyzed neuropsychological memory performance in patients with a clinical diagnosis of bvFTD divided into those who progressed (n ϭ 50) and those who remained stable (n ϭ 39), patients with AD (n ϭ 64), and healthy controls (n ϭ 64). Results:Patients with progressive bvFTD were impaired on most memory tests to a similar level to that of patients with early AD. Findings from a subset of patients with progressive bvFTD with confirmed FTLD pathology (n ϭ 10) corroborated these findings. By contrast, patients with phenocopy bvFTD performed significantly better than progressors and patients with AD. Logistic regression revealed that patients with bvFTD can be distinguished to a high degree (85%) on the immediate recall score of a word list learning test (Rey Auditory Verbal Learning Test). Conclusions:Our results provide evidence for an underlying memory deficit in "real" or progressive behavioral variant frontotemporal dementia (bvFTD) similar to Alzheimer disease, though the groups differ in orientation scores, with patients with bvFTD being intact. Exclusion solely based on impaired neuropsychological memory performance can potentially lead to an underdiagnosis of FTD. Neurology Our study focuses on episodic memory in frontotemporal dementia (FTD). "Severe amnesia" is currently an exclusion criterion for the behavioral subtype of FTD (bvFTD), 1 yet 10% of pathologically confirmed cases have reported memory symptoms in the initial stages of disease, 2 and occasional cases have severe amnesia, 3 as emphasized in early descriptions of Pick's. 4 Recently this and other findings have put into question the reliability of current diagnostic criteria for bvFTD. [5][6][7] To date, surprisingly few studies have investigated episodic memory in bvFTD, with inconsistent results. Such inconsistency could, at least in part, be explained by recent studies which have shown that clinically diagnosed patients with bvFTD vary in their prognosis [8][9][10] ; some show rapid progression while others show little or no progression over a decade. The 2 patient groups can be discriminated on MRI and PET findings despite exhibiting equivalent degrees of behavioral disturbance. [8][9][10] This heterogeneity of bvFTD might explain previous findings: if only the progressive group shows brain atrophy, then this group is more likely to exhibit From the Prince

Lost and Forgotten? Orientation Versus Memory in Alzheimer's Disease and Frontotemporal Dementia

“…Furthermore, bvFTD and AD patients differed on the memory scores with more severe impairment in AD. This replicates our previous findings [2] which also showed a similar "step-function" of bvFTD and AD memory performance with bvFTD patients showing a lesser memory impairment than AD. Prior studies [19] showed an even milder memory impairment in bvFTD, which might have been due to the inclusion of so called phenocopy cases, who generally do not show memory impairments [2].…”

“…This replicates our previous findings [2] which also showed a similar "step-function" of bvFTD and AD memory performance with bvFTD patients showing a lesser memory impairment than AD. Prior studies [19] showed an even milder memory impairment in bvFTD, which might have been due to the inclusion of so called phenocopy cases, who generally do not show memory impairments [2]. Phenocopy cases mimic the behavioral symptoms of bvFTD but do not progress in their disease, show no macroscopic brain atrophy, and perform at control level for most neuropsychological tests.…”

“…Thus Pittsburgh Compound B scanning or cerebrospinal fluid testing of future sample will be important to confirm our results. Still, our memory findings are in keeping with studies using pathological confirmed cases of bvFTD [2,3], supporting therefore the validity of the current findings.…”

“…Single case reports [3] have confirmed that patients with pathologically confirmed bvFTD can have severe amnesia, while a retrospective study [2] of bvFTD cases, a proportion of whom came to autopsy, showed that a high percentage had memory impairment of the same magnitude as seen in AD. This is further corroborated via imaging studies showing similar levels of hippocampal atrophy in bvFTD and AD [4][5][6], although this can vary for bvFTD patients [7].…”

“…A potential diagnostic distinction between AD and bvFTD, however, may be the ability to correctly identify one's location in space and time. AD patients are known to experience disorientation from an early stage [8]; clinical reports suggest that orientation is intact in bvFTD cases [2], although this has not been explored systematically.…”