Cerebrospinal Fluid and Plasma Biomarkers do not Differ in the Presenile and Late-Onset Behavioral Variants of Frontotemporal Dementia.

Background: Memory troubles and hippocampal atrophy are considered more frequent and focal atrophy less severe in late-onset (>65 years) than in presenile behavioral variant of frontotemporal dementia (bvFTD).

Objective: To compare cerebrospinal fluid (CSF) and plasma biomarkers in late-onset and presenile bvFTD.

Methods: Multicentric retrospective study (2007-2017) on patients with clinical diagnosis of bvFTD.

Results: This study included 44 patients (67%) with presenile and 22 (33%) with late-onset bvFTD (comparable mean disease duration; n = 11 with causal mutations). Hippocampal atrophy was more frequent (80% versus 25.8%) and severe in late-onset bvFTD (median Scheltens score: 3 [0-4] versus 1 [0-3]), without difference after adjustment for age. Lobar atrophy and focal hypometabolism/hypoperfusion were not different between groups. The median CSF Aβ1-42 and phosphorylated tau (P-tau) concentrations were in the normal range and comparable between groups. Axonal neurodegeneration biomarkers were within the normal range (CSF T-tau; plasma T-tau in late-onset bvFTD) or higher (plasma neurofilament light chain (NFL); plasma T-tau in presenile bvFTD) than the normal values, but globally not different between bvFTD groups. Plasma glial fibrillary acid protein (GFAP) was strongly increased in both bvFTD groups compared with the values in controls of the same age.

Conclusion: The CSF and plasma biomarker profiles did not suggest a more aggressive neurodegeneration in the presenile group (comparable T-tau, NFL, and GFAP levels) or the co-existence of Alzheimer's disease in the late-onset group (comparable and within normal range CSF Aβ1-42 and P-tau). The severity of the neurodegenerative process seems comparable in presenile and late-onset bvFTD.