Language impairment in the genetic forms of behavioural variant frontotemporal dementia
Authors: Samra Kiran , MacDougall Amy M. , Bouzigues Arabella , Bocchetta Martina , Cash David M. , Greaves Caroline V. , Convery Rhian S. , van Swieten John C. , Seelaar Harro , Jiskoot Lize , Moreno Fermin , Sanchez-Valle Raquel , Laforce Robert , Graff Caroline , Masellis Mario , Tartaglia Maria Carmela , Rowe James B. , Borroni Barbara , Finger Elizabeth , Synofzik Matthis , Galimberti Daniela , Vandenberghe Rik , de Mendonça Alexandre , Butler Christopher R. , Gerhard Alexander , Ducharme Simon , Le Ber Isabelle , Tiraboschi Pietro , Santana Isabel , Pasquier Florence , Levin Johannes , Otto Markus , Sorbi Sandro , Rohrer Jonathan D. , Russell Lucy L. ,   On Behalf of the Genetic FTD Initiative (GENFI), Nelson Annabel , Thomas David L. , Todd Emily , Benotmane Hanya , Nicholas Jennifer , Shafei Rachelle , Timberlake Carolyn , Cope Thomas , Rittman Timothy , Benussi Alberto , Premi Enrico , Gasparotti Roberto , Archetti Silvana , Gazzina Stefano , Cantoni Valentina , Arighi Andrea , Fenoglio Chiara , Scarpini Elio , Fumagalli Giorgio , Borracci Vittoria , Rossi Giacomina , Giaccone Giorgio , Di Fede Giuseppe , Caroppo Paola , Tiraboschi Pietro , Prioni Sara , Redaelli Veronica , Tang-Wai David , Rogaeva Ekaterina , Castelo-Branco Miguel , Freedman Morris , Keren Ron , Black Sandra , Mitchell Sara , Shoesmith Christen , Bartha Robart , Rademakers Rosa , Poos Jackie , Papma Janne M. , Giannini Lucia , van Minkelen Rick , Pijnenburg Yolande , Nacmias Benedetta , Ferrari Camilla , Polito Cristina , Lombardi Gemma , Bessi Valentina , Veldsman Michele , Andersson Christin , Thonberg Hakan , Öijerstedt Linn , Jelic Vesna , Thompson Paul , Langheinrich Tobias , Lladó Albert , Antonell Anna , Olives Jaume , Balasa Mircea , Bargalló Nuria , Borrego-Ecija Sergi , Verdelho Ana , Maruta Carolina , Ferreira Catarina B. , Miltenberger Gabriel , do Couto Frederico Simões , Gabilondo Alazne , Gorostidi Ana , Villanua Jorge , Cañada Marta , Tainta Mikel , Zulaica Miren , Barandiaran Myriam , Alves Patricia , Bender Benjamin , Wilke Carlo , Graf Lisa , Vogels Annick , Vandenbulcke Mathieu , Van Damme Philip , Bruffaerts Rose , Poesen Koen , Rosa-Neto Pedro , Gauthier Serge , Camuzat Agnès , Brice Alexis , Bertrand Anne , Funkiewiez Aurélie , Rinaldi Daisy , Saracino Dario , Colliot Olivier , Sayah Sabrina , Prix Catharina , Wlasich Elisabeth , Wagemann Olivia , Loosli Sandra , Schönecker Sonja , Hoegen Tobias , Lombardi Jolina , Anderl-Straub Sarah , Rollin Adeline , Kuchcinski Gregory , Bertoux Maxime , Lebouvier Thibaud , Deramecourt Vincent , Santiago Beatriz , Duro Diana , Leitão Maria João , Almeida Maria Rosario , Tábuas-Pereira Miguel , Afonso Sónia 
Published: December 2022

Abstract
Background
Behavioural variant fronto-temporal dementia (bvFTD) is characterised by a progressive change in personality in association with atrophy of the frontal and temporal lobes. Whilst language impairment has been described in people with bvFTD, little is currently known about the extent or type of linguistic difficulties that occur, particularly in the genetic forms.

Methods
Participants with genetic bvFTD along with healthy controls were recruited from the international multicentre Genetic FTD Initiative (GENFI). Linguistic symptoms were assessed using items from the Progressive Aphasia Severity Scale (PASS). Additionally, participants undertook the Boston Naming Test (BNT), modified Camel and Cactus Test (mCCT) and a category fluency test. Participants underwent a 3T volumetric T1-weighted MRI, with language network regional brain volumes measured and compared between the genetic groups and controls.

Results
76% of the genetic bvFTD cohort had impairment in at least one language symptom: 83% C9orf72, 80% MAPT and 56% GRN mutation carriers. All three genetic groups had significantly impaired functional communication, decreased fluency, and impaired sentence comprehension. C9orf72 mutation carriers also had significantly impaired articulation and word retrieval as well as dysgraphia whilst the MAPT mutation group also had impaired word retrieval and single word comprehension. All three groups had difficulties with naming, semantic knowledge and verbal fluency. Atrophy in key left perisylvian language regions differed between the groups, with generalised involvement in the C9orf72 group and more focal temporal and insula involvement in the other groups. Correlates of language symptoms and test scores also differed between the groups.

Conclusions
Language deficits exist in a substantial proportion of people with familial bvFTD across all three genetic groups. Significant atrophy is seen in the dominant perisylvian language areas and correlates with language impairments within each of the genetic groups. Improved understanding of the language phenotype in the main genetic bvFTD subtypes will be helpful in future studies, particularly in clinical trials where accurate stratification and monitoring of disease progression is required.