Macular thickness and peripapillary RNFL thickness in frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS)

Abstract

Purpose : Frontotemporal dementia (FTD) includes a group of neurodegenerative syndromes associated with two main proteinopathies: tauopathy and TAR DNA-binding protein 43 (TDP-43) proteinopathy. The difficulty of predicting underlying pathology in vivo in FTD precludes the delivery of targeted therapy. Some syndromes are reliably associated with either tau (progressive supranuclear palsy [PSP]) or TDP-43 (semantic variant primary progressive aphasia [svPPA] and amyotrophic lateral sclerosis [ALS]). We compared macular retinal thickness and peripapillary retinal nerve fibre layer (pRNFL) thickness between participants with tauopathy (PSP) and TDP-43 proteinopathy (svPPA and ALS) to examine the potential of spectral domain optical coherence tomography (SD-OCT) as an inexpensive, non-invasive tool to detect possible retinal biomarkers differentiating these pathologies in vivo.

Methods : This was an analysis of a prospective, multi-centre, observational study. Macular and pRNFL SD-OCT images were acquired in both eyes of each participant using the Heidelberg Spectralis (Heidelberg, Germany) as part of the Ontario Neurodegenerative Disease Research Initiative. We analyzed macular thickness in the central 1mm diameter zone, four sectors (superior, inferior, nasal, and temporal) within a 3mm diameter circular grid centred on the fovea, as well as global and sectoral pRNFL thicknesses. Linear mixed model methods adjusting for age and gender were used to compare the thickness values between the tau (PSP) and TDP-43 (svPPA and ALS) groups.

Results : Mean group ages for tauopathy (9 eyes of 5 subjects) and TDP-43 (34 eyes of 17 subjects) were 72.7 (SD=5.2) and 62.2 (SD=9.1) years, respectively. We found no significant difference between mean retinal thickness in the central macular zone of the tauopathy (272.21μm, SD=9.81) and TDP-43 (274.35μm, SD=4.76) groups (p=0.852). A trend to statistically different mean pRNFL thickness was found in the inferior-nasal sector between the groups, with the tauopathy group having a thicker pRNFL (difference in means=20.99μm, SD=10.84, p=0.068).

Conclusions : There was no significant difference in macular or pRNFL thickness between tauopathy and TDP-43 groups, although there was a general trend for global and sectoral pRNFL to be thicker in the tauopathy group. Future work should include larger sample sizes, longitudinal analysis, and sub-layer analysis.

This is a 2020 ARVO Annual Meeting abstract.