Diagnostic utility of FDG-PET in the differential diagnosis between different forms of primary progressive aphasia

Femke Bouwman, ,Silvia Morbelli,Cristina Festari,Federica Gandolfo,Marina Boccardi,Javier Arbizu,Daniele Altomare,Alexander Drzezga,Federica Agosta,Stefania Orini,Peter Nestor,Zuzana Walker,Flavio Nobili

doi:10.1007/s00259-018-4034-z

Abstract

PurposeA joint effort of the European Association of Nuclear Medicine (EANM) and the European Academy of Neurology (EAN) aims at clinical guidance for the use of FDG-PET in neurodegenerative diseases. This paper addresses the diagnostic utility of FDG-PET over clinical/neuropsychological assessment in the differentiation of the three forms of primary progressive aphasia (PPA).MethodsSeven panelists were appointed by the EANM and EAN and a literature search was performed by using harmonized PICO (Population, Intervention, Comparison, Outcome) question keywords. The studies were screened for eligibility, and data extracted to assess their methodological quality. Critical outcomes were accuracy indices in differentiating different PPA clinical forms. Subsequently Delphi rounds were held with the extracted data and quality assessment to reach a consensus based on both literature and expert opinion.ResultsCritical outcomes for this PICO were available in four of the examined papers. The level of formal evidence supporting clinical utility of FDG-PET in differentiating among PPA variants was considered as poor. However, the consensual recommendation was defined on Delphi round I, with six out of seven panelists supporting clinical use.ConclusionsQuantitative evidence demonstrating utility or lack thereof is still missing. Panelists decided consistently to provide interim support for clinical use based on the fact that a typical atrophy or metabolic pattern is needed for PPA according to the diagnostic criteria, and the synaptic failure detected by FDG-PET is an earlier phenomenon than atrophy. Also, a normal FDG-PET points to a non-neurodegenerative cause.

Highlights

In the lack of clinical guidelines for the use of FDG-PET to diagnose dementing neurodegenerative conditions, the European Association of Nuclear Medicine (EANM) and the European Academy of Neurology (EAN) launched a joint effort aimed at providing clinicians with clinical guidance for using the exam
We report the availability of evidence supporting the use of FDG-PET for the differential diagnosis between different forms of primary progressive aphasia (PPA)
Panelists kept that specific patterns of atrophy and/or hypometabolism are necessary for the diagnosis of PPA according to the diagnostic criteria and FDG-PET is more sensitive than MRI [2]

Summary

Introduction

In the lack of clinical guidelines for the use of FDG-PET to diagnose dementing neurodegenerative conditions, the European Association of Nuclear Medicine (EANM) and the European Academy of Neurology (EAN) launched a joint effort aimed at providing clinicians with clinical guidance for using the exam To this avail, a set of 21 clinical questions was defined to perform literature searches and assessment of the evidence supporting FDG-PET clinical use, and feeding a group of experts defining consensual [1]. Clinical criteria for the three variants of PPA—nonfluent/ agrammatic, semantic, and logopenic—were developed by an international group of PPA investigators [2] This classification can be further specified as Bimaging-supported^ if the expected pattern of atrophy or hypometabolism is found, and Bwith definite pathology^ if pathologic or genetic data are available. FDG-PET is used on a regular basis in clinical practice for the diagnosis of PPA types

Results

Discussion

Conclusion