RT Journal Article SR Electronic T1 Primary Progressive Aphasia (PPA) variants: a diagnostic brain 18F-FDG PET/CT study JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1662 OP 1662 VO 59 IS supplement 1 A1 Susanna Nuvoli A1 Silvia Contu A1 Bi Llie Joy Pung A1 Sarah Galassi A1 Maria Lina Stazza A1 Giuseppe Madeddu A1 Angela Spanu YR 2018 UL http://jnm.snmjournals.org/content/59/supplement_1/1662.abstract AB 1662Objectives: he progression of PPA variants is advisable to be recognized in advance since the disorders might evolve in Alzheimer disease (AD), such as logopenic aphasia (LPA), or in fronto-temporal dementia (FTD), such as progressive fluent aphasia (PNFA) and semantic aphasia (SA). For this purpose, we evaluated 18F-FDG PET/CT diagnostic usefulness in PPA variants. Methods: We retrospectively enrolled 26 consecutive patients, 13 with clinical symptoms suspect of PPA (Group 1) and 13 with ascertained PPA with symptoms of early AD or FTD (Group 2). All patients underwent brain 18F-FDG PET/CT using Discovery 710 tomograph (GE Healthcare) and evaluating the images both qualitatively and quantitatively with automated analysis program (Cortex ID-GE Healthcare); brain metabolic map and normal age matched control group comparative analysis was performed. RESULTS: Brain 18F-FDG PET/CT showed different hypometabolic patterns with reduced cortical uptakes in the two different groups ordering these according to lesion severity. Group 1: diffuse hypometabolism in 1/13 cases and diffuse in bilateral fronto-parietal and fronto-temporal regions in 1/13 cases; reduced metabolism in bilateral temporo-parietal regions in 2/13 cases, in left fronto-parietal inferior regions in 5/13 cases, in inferior frontal and temporal regions in 3/13 cases and in left inferior frontal region in 1/13 cases. Group 2: diffuse hypometabolism in 2/13 cases; reduced metabolism in fronto-temporal and fronto-parietal regions bilaterally in 6/13 cases, and in bilateral temporo-parietal regions in 5/13 cases. The 9 Group 1 patients with hypometabolic areas only in inferior frontal regions as well as in inferior parietal and temporal regions were clinically classified as PNFA at risk to develop FTD, while the two patients with bilateral hypometabolism in temporo-parietal regions were classified as LPA, eventually anticipating AD. However, in the two patients with diffuse hypometabolism the diagnosis remained uncertain. The six Group 2 patients with hypometabolism in fronto-temporal and fronto-parietal areas were classified as PNFA and SA, respectively, both associated to FTD, while the five patients with temporo-parietal hypometabolism were classifieds as LPA associated to AD. However, the diagnosis remained uncertain in the remaining two cases with diffuse hypometabolism. CONCLUSION: The present study further underlines the difficulty in clinical differential diagnosis of PPA different variants that that could evolve into AD/FTD. Brain 18F-FDG PET/CT proved valuable tool in supporting the clinical diagnosis of primary PPA eventually evolving into AD/FTD as well as in contributing to identify PPA already associated to AD/FTD since, in our cases, the diagnosis was achieved in 84.6% of both Groups. However, 18F-FDG PET/CT could not clarify the four cases with diffuse cortical hypometabolism whose diagnosis remained uncertain; only a more accurate clinical and instrumental investigation and a close follow up might guide to correct diagnosis. A large number of cases monitored over time could confirm these data.