Tau‐PET imaging with 18F‐PI‐2620 reveals lateralized distribution of tau pathology in critical language regions in patients with early onset of Alzheimer’s Disease and patients with primary progressive aphasia

Abstract

AbstractBackgroundLanguage disorders are frequent in patients in advanced and early stages of dementia (Goth & Strøm, 2018) together with the deterioration of other cognitive domains (e.g., memory) (Taler & Phillips, 2008). The first complaint in people with dementia often is language impairment, even preceding other cognitive declines (Ferris & Farlow, 2013). Logopenic variant primary progressive aphasia (lvPPA) and non‐fluent/agrammatic variant PPA (nf/avPPA) are rare neurodegenerative disorders being language impairment the main feature (Gono‐Tempini, 2011). Both β‐amyloid (Aβ) and tau appear to occur in Alzheimer disease (AD). Moreover, Aβ and tau aggregates also represent the underlying pathology in lvPPA (Montembeault et al. 2018) while nf/avPPA resembles a pure tau‐pathology. The purpose of this study is to explore the distribution of tau‐pathology in critical language regions in patients with early‐onset AD (EOAD) and patients diagnosed with primary progressive aphasia (PPA).MethodEight participants (55‐77y): 4 with EOAD, 3 with lvPPA (these first seven patients additionally had a positive 18F‐Florbetaben Amyloid PET), 1 with nf/avPPA, and 14 healthy controls (HC) (age range 54‐76y) underwent dynamic PET scans with 18F‐PI‐2620 to examine the distribution of tau‐pathology in the following cortical language regions: inferior frontal gyrus (IFG), superior temporal gyrus (STG), supramarginal and angular gyrus (PL). Group differences in language regions were examined using standardized uptake value ratios (SUVRs) normalized to the inferior gray matter of the cerebellum.ResultCompared to HC, 3/4 patients with EOAD showed elevated levels of 18F‐PI‐2620 binding, mainly in the right IFG and IPL and left STG, while 3/4 patients with PPA (2 lvPPA and 1 nf/avPPA) showed left lateralized elevated uptake of 18F‐PI‐2620 in all language regions. All PPA patients showed increased binding of 18F‐PI‐2620 predominantly in the left parietal regions.ConclusionOur preliminary results reveal a lateralized distribution pattern of 18F‐PI‐2620 in language regions in patients with EOAD and particularly in those with PPA. These findings suggest that 18F‐PI‐2620 PET imaging is a promising tool to visualize tau aggregations in patients with EOAD and PPA. However, further studies are needed to confirm these preliminary results.