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Rates of Decline and Survival in FTLD and Its Subtypes

Survival is worse with FTLD than with AD, even among patients with comparable baseline cognitive status.

To compare rates of progression and survival in frontotemporal lobar degenerations (FTLD, a category that includes frontotemporal dementia and the progressive aphasias) and in Alzheimer disease (AD), researchers tracked dementia patients at seven centers and recorded autopsy diagnoses. They then compared data from 70 autopsy-confirmed FTLD cases and 70 confirmed AD cases, matched to FTLD cases by demographic and cognitive status at initial evaluation.

Overall, the FTLD group had a less favorable survival rate than the AD group (median survival after initial evaluation, 4.2 years vs. 6.0 years). Compared to FTLD patients with tau-positive pathology, FTLD patients with tau-negative pathology had a worse survival rate. The survival rate in tau-positive patients was similar to that in AD patients.

Uniquely, the authors compared 1-year changes in scores on cognitive-status testing and activities-of-daily-living inventories across groups. Scores declined faster in the FTLD group than in the AD group. Despite the survival differences, the two pathologic subtypes of FTLD declined at about the same rates.

Comment: FTLD is clinically and pathologically heterogeneous. In this study, the authors identified two pathologic subtypes. This study as well as others showed that tau-negative FTLD (which almost always is accompanied by ubiquitin-positive inclusions) confers worse survival than do the other FTLD subtypes and AD (Neurology 2005; 65:719, Neurology 2005; 65:645, Brain 2005 128:1996, and Neurology 2003; 61:349). Tau-negative FTLD includes patients who also have motor neuron disease, which is known to confer a poor prognosis. The current report does not mention whether the FTLD patients had motor neuron disease. Despite its influence on survival, pathologic subtype did not influence the 1-year rate of decline on clinical assessments. The differences between subtypes of FTLD and AD highlight the importance of clinical recognition of FTLD for predicting outcomes more accurately.

— David Knopman, MD

Dr. Knopman is Professor of Neurology, Mayo Clinic College of Medicine, Rochester, MN.

Published in Journal Watch Neurology November 3, 2005

Citation(s):

Rascovsky K et al. Rate of progression differs in frontotemporal dementia and Alzheimer disease. Neurology 2005 Aug 9; 65:397-403.

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