Neuropsychological decline in frontotemporal lobar degeneration: A longitudinal analysis.

Abstract

Few studies have assessed whether the patterns of neuropsychological impairment in patients with different frontotemporal lobar degeneration (FTLD) subtypes remain distinct over the duration of their illness or devolve into a common, undifferentiated neuropsychological state. A longitudinal neuropsychological analysis was obtained over 100 months assessing executive control, language/ naming, and visuoconstruction in 441 patients diagnosed with Alzheimer's disease (AD) and four FTLD subtypes, i.e., a social comportment/dysexecutive (SOC/EXEC) disorder; progressive nonfluent aphasia (PNFA); semantic dementia (SemD); and corticobasal degeneration (CBD). Initial group differences on each measure were maintained over the duration of illness, including several double dissociations. For example, AD patients exhibited a decline in 'animal' fluency; PNFA Correspondence concerning this article should be addressed to David J. Libon, Department of Neurology, Drexel University College of Medicine, Philadelphia, PA 19129. E-mail: dlibon@drexelmed.edu. NIH Public Access Author ManuscriptNeuropsychology. Author manuscript; available in PMC 2010 May 1. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript patients had difficulty on tests of executive control, SemD maintained their impairment on tests of naming, and CBD had presented with performance on visuoconstructional tests. None of the group by neuropsychological task interactions evaluating longitudinal decline was significant, suggesting that performance does not converge onto a common subtype over time. These data indicate that distinct patterns of neuropsychological impairment are maintained longitudinally, reflecting the unique anatomic distribution of relative disease burden in AD and FTLD.Keywords frontotemporal dementia; Alzheimer's disease; longitudinal assessmentFrontotemporal lobar degeneration (FTLD) is a progressive neurodegenerative illness presenting with imaging and autopsy evidence of frontal and temporal alterations (McKhann et al., 2001;Snowden, Neary, & Mann, 1996). Major FTLD subtypes that have been identified include a social/dysexecutive (SOC/EXEC) syndrome, progressive nonfluent aphasia (PNFA), semantic dementia (SemD), and corticobasal degeneration (CBD). In this study, we examined the longitudinal course of the neuropsychological profiles of these patient groups to determine whether their initial neuropsychological deficits are maintained over time, or whether these distinctions are lost as the disease progresses such that they merge into a single, end-stage clinical dementia profile. This issue has clinical as well as theoretical implications.Past neuropsychological studies have tended to focus on the initial, cross-sectional differences that may distinguish FTLD from Alzheimer's disease (AD; Kramer et al., 2003;Libon, Massimo, et al., 2007;Libon, Xie, et al., 2007). For example, Libon, Massimo, et al. (2007) studied a large sample of AD and FTLD patients and subjected their performance on a comprehensive neuropsychol...

Progression of language decline and cortical atrophy in subtypes of primary progressive aphasia

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Dissociable executive functions in behavioral variant frontotemporal and Alzheimer dementias

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