DIAGNOSTIC UTILITY OF FDG-PET IN DIFFERENTIATING BETWEEN LEWY BODY DEMENTIA AND FRONTOTEMPORAL LOBAR DEGENERATION

Abstract

We performed a systematic review to assess the available evidence for FDG-PET utility in the differential diagnosis between Lewy body dementia (LBD) and fronto-temporal lobar degeneration (FTLD) in difficult to diagnose cases. The search was performed on PubMed, Embase and Cochrane on January 4th, 2016. Critical outcomes were improvement in the sensitivity and specificity of FDG-PET in distinguishing between LBD and FTLD patients as compared to standard clinical/neuropsychological assessment alone. Assessment was required versus gold- (pathology or biomarker) or reference-standard (clinical confirmation at follow-up). No minimum sample size was set a priori. Data were extracted and assessed as to publication bias, heterogeneity, imprecision, risk of bias, indirectness, and applicability. We provide assessment of the quality of evidence, of the target effect, and of strength of recommendation. Out of the 13 papers obtained, only one reported the outcomes of interest. Moreover, sensitivity and specificity were assessed versus baseline clinical diagnosis, in the absence of any gold- or reference-standard. This study* included a total of 98 FTLD and 27 LBD patients, and provides a very low level of evidence for moderate sensitivity and low specificity of FDG-PET in distinguishing between LBD and FTLD patients (Table). Concerns regarding applicability are due to the use of semiquantitative methods of image analysis (increasingly but not routinely adopted in the clinical context). Patterns of hypometabolism associated with the two disorders denote predominantly posterior hypometabolism in LBD and predominantly anterior hypometabolism in FTLD patients, but also a significant overlap (i.e., parietotemporal cortex, posterior cingulate). The available data provide very low evidence for low diagnostic utility of FDG-PET for the differential diagnosis between LBD and FTLD. The available evidence supports a weak recommendation for using FDG-PET to differentiate between LBD and FTLD in doubtful case, and further research is warranted for a proper assessment of its incremental value for this diagnostic question. *Mosconi L. et al., Multicenter standardized 18F-FDG PET diagnosis of mild cognitive impairment, Alzheimer's disease, and other dementias. J Nucl Med. 2008 Mar;49(3):390–8.