Distinct [18F]THK5351 binding patterns in primary progressive aphasia variants

Jolien Schaeverbeke,Yolande Pijnenburg,Michel Koole,Guy Bormans,Lieven Declercq,Rik Vandenberghe,Anne Sieben,Rose Bruffaerts,Eva Dries,Patrick Dupont,Ronald Peeters,Koen Van Laere,Charlotte Evenepoel,Karen Van Bouwel,Karen Meersmans,Silvy Gabel,Kate Adamczuk

doi:10.1007/s00259-018-4075-3

Abstract

PurposeTo assess the binding of the PET tracer [18F]THK5351 in patients with different primary progressive aphasia (PPA) variants and its correlation with clinical deficits. The majority of patients with nonfluent variant (NFV) and logopenic variant (LV) PPA have underlying tauopathy of the frontotemporal lobar or Alzheimer disease type, respectively, while patients with the semantic variant (SV) have predominantly transactive response DNA binding protein 43-kDa pathology.MethodsThe study included 20 PPA patients consecutively recruited through a memory clinic (12 NFV, 5 SV, 3 LV), and 20 healthy controls. All participants received an extensive neurolinguistic assessment, magnetic resonance imaging and amyloid biomarker tests. [18F]THK5351 binding patterns were assessed on standardized uptake value ratio (SUVR) images with the cerebellar grey matter as the reference using statistical parametric mapping. Whole-brain voxel-wise regression analysis was performed to evaluate the association between [18F]THK5351 SUVR images and neurolinguistic scores. Analyses were performed with and without partial volume correction.ResultsPatients with NFV showed increased binding in the supplementary motor area, left premotor cortex, thalamus, basal ganglia and midbrain compared with controls and patients with SV. Patients with SV had increased binding in the temporal lobes bilaterally and in the right ventromedial frontal cortex compared with controls and patients with NFV. The whole-brain voxel-wise regression analysis revealed a correlation between agrammatism and motor speech impairment, and [18F]THK5351 binding in the left supplementary motor area and left postcentral gyrus. Analysis of [18F]THK5351 scans without partial volume correction revealed similar results.Conclusion[18F]THK5351 imaging shows a topography closely matching the anatomical distribution of predicted underlying pathology characteristic of NFV and SV PPA. [18F]THK5351 binding correlates with the severity of clinical impairment.

Highlights

Primary progressive aphasia (PPA) is a neurodegenerative syndrome which primarily affects speech and language, with relative preservation of other cognitive domains [1]
Patients with nonfluent variant (NFV) showed increased binding in the supplementary motor area, left premotor cortex, thalamus, basal ganglia and midbrain compared with controls and patients with semantic variant (SV)
Patients with SV had increased binding in the temporal lobes bilaterally and in the right ventromedial frontal cortex compared with controls and patients with NFV

Summary

Introduction

Primary progressive aphasia (PPA) is a neurodegenerative syndrome which primarily affects speech and language, with relative preservation of other cognitive domains [1]. NFV PPA present with agrammatism and/or speech apraxia, whereas patients with SV PPA have single-word comprehension and naming deficits [1]. Patients with LV PPA show deficient single-word retrieval in spontaneous speech and a shortterm phonological memory deficit [1]. Of patients with NFV, 50–70% have underlying frontotemporal lobar degeneration (FTLD) tauopathy [2,3,4]. FTLD tauopathy can be four-repeat (4R) tau due to corticobasal degeneration (CBD) or progressive supranuclear palsy (PSP), which is localized in the basal ganglia, brainstem and cerebral cortex [5], or, less frequently, binding protein 43-kDa (TDP-43) pathology, usually of type A [2], and 12–25% have Alzheimer disease (AD) pathology [3, 4] (for review see [6]), characterized by neurofibrillary tangles composed of balanced 3R/4R tau, and fibrillar amyloid plaques.

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