Anne Bertrand MD, PhD, Presenter: Nothing to Disclose

Fatima Ameur MD, Abstract Co-Author: Nothing to Disclose

Paola Caroppo MD, Abstract Co-Author: Nothing to Disclose

Didier Dormont MD, Abstract Co-Author: Nothing to Disclose

Alexis Brice, Abstract Co-Author: Nothing to Disclose

Isabelle Le Ber, Abstract Co-Author: Nothing to Disclose

Olivier Colliot, Abstract Co-Author: Nothing to Disclose

To study the MR phenotypes of the 2 most frequent genetic forms of frontotemporal dementia: PGRN and C9ORF72 mutations.

2 readers retrospectively reviewed axial FLAIR and 3DT1 images of 27 patients with a genetic form of frontotemporal dementia: 17 patients with C9ORF72 mutation and 10 patient with PGRN mutation. The severity of FLAIR hyperintensity was rated using the Fazekas & Schmidt score. The type of FLAIR hyperintensities was rated using a 3-level score: A- vascular type; B- vascular type predominating in the areas of atrophy; C-non vascular type. The presence of regional atrophy was scored as follow: presence or absence of an anteroposterior gradient of atrophy; presence or absence of a left-to-right or right-to-left gradient of atrophy.

Interrater agreement was moderate for Fazekas & Schmidt score (0.50 {0.16-0,68}) and was high for the type of FLAIR intensities (0.79 {0.56-0.91}), the presence of anteroposterior gradient of atrophy (0.78 {0.61-1}) and the presence of left-to-right or right-to-left gradient of atrophy (0.73 {0.52-0,94}) (weighted kappa tests). Atypical FLAIR hyperintensities (type B-C) were present in 90% of patients with PGRN mutation, while only 12% with C9ORF72 mutation. Asymmetrical anterior atrophy, characteristic of frontotemporal dementia, was present in 70% of patients with PGRN mutation, while only 18% of patients with C9ORF72 mutation.

Major phenotypic differences distinguish on brain MRI C9ORF72 and PGRN mutations, which are both related to frontotemporal dementia with TDP-43 inclusions. This result demonstrates that gene-related effects can overpass lesion-related effects in the phenotypic expression of frontotemporal dementias.

In patients presenting with frontotemporal dementia, neuroradiologists should raise the possibility of a genetic form linked to PGRN mutation when atrophy is particularly marked, and associated with atypical FLAIR hyperintensities, predominating in the areas of atrophy.

Bertrand, A, Ameur, F, Caroppo, P, Dormont, D, Brice, A, Le Ber, I, Colliot, O, Genetic Frontotemporal Dementia with TDP-43 Inclusions: Distinct Radiological Phenotypes between Patients with PGRN and C9ORF72 Mutations.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14045777.html