Characteristics and progression of patients with frontotemporal dementia in a regional memory clinic network
Authors: Leroy Mélanie , Bertoux Maxime , Skrobala Emilie , Mode Elisa , Adnet-Bonte Catherine , Le Ber Isabelle , Bombois Stéphanie , Cassagnaud Pascaline , Chen Yaohua , Deramecourt Vincent , Lebert Florence , Mackowiak Marie Anne , Sillaire Adeline Rollin , Wathelet Marielle , Pasquier Florence , Lebouvier Thibaud ,   the Méotis network, Abied Rachid , Adnet Cathrine , Barois Arnaud , Baude Stéphanie , Berriot Véronique , Bombois Stéphanie , Boyer Gloria , Brique Didier , Calais Gauthier , Cassagnaud Pascaline , Drchekroud Hacène , Chen Yaohua , Cliche Joel , Crinquette Charlotte , Dachy Valérie , Debock Valerie , Deprez Anne , Deramecourt Vincent , Dereeper Olivier , Devos Philippe , Elazouzi Abdelghani , Enderle Adeline , Fanjaud Nicolas , Forzy Pierre , Gallouj Karim , Garcon Karine , Honore Marie , Huvent Dominique , Idiri Houria , Ladeiro Annabelle , Lavenu Isabelle , Lebert Florence , Lebouvier Thibaud , Le Coz Patrick , Leclercq Eugénie , Lefebvre Denis , Maciejasz Pierre , Mackowiak Marie-Anne , Messin Rémi , Pasquier Florence , Petit Valérie , Plichon Christine , Ponthieu Sandrine , Quievre Cécile , Roche Jean , Rollin Sillaire Adeline , Rosolacci Thierry , Senechal Olivier , Taillez Nathalie , Thibault Tanchou Stéphanie , Tison Frédéric , Tollot Sarah , Trocmet Marie , Verpoort Charlotte 
Published: January 2021

Abstract
Background
Due to heterogeneous clinical presentation, difficult differential diagnosis with Alzheimer’s disease (AD) and psychiatric disorders, and evolving clinical criteria, the epidemiology and natural history of frontotemporal lobar degeneration (FTD) remain elusive. In order to better characterize FTD patients, we relied on the database of a regional memory clinic network with standardized diagnostic procedures and chose AD patients as a comparator.

Methods
Patients that were first referred to our network between January 2010 and December 2016 and whose last clinical diagnosis was degenerative or vascular dementia were included. Comparisons were conducted between FTD and AD as well as between the different FTD syndromes, divided into language variants (lvFTD), behavioral variant (bvFTD), and FTD with primarily motor symptoms (mFTD). Cognitive progression was estimated with the yearly decline in Mini Mental State Examination (MMSE).

Results
Among the patients that were referred to our network in the 6-year time span, 690 were ultimately diagnosed with FTD and 18,831 with AD. Patients with FTD syndromes represented 2.6% of all-cause dementias. The age-standardized incidence was 2.90 per 100,000 person-year and incidence peaked between 75 and 79 years. Compared to AD, patients with FTD syndromes had a longer referral delay and delay to diagnosis. Patients with FTD syndromes had a higher MMSE score than AD at first referral while their progression was similar. mFTD patients had the shortest survival while survival in bvFTD, lvFTD, and AD did not significantly differ. FTD patients, especially those with the behavioral variant, received more antidepressants, anxiolytics, and antipsychotics than AD patients.

Conclusions
FTD syndromes differ with AD in characteristics at baseline, progression rate, and treatment. Despite a broad use of the new diagnostic criteria in an organized memory clinic network, FTD syndromes are longer to diagnose and account for a low proportion of dementia cases, suggesting persistent underdiagnosis. Congruent with recent publications, the late peak of incidence warns against considering FTD as being exclusively a young-onset dementia.