Memories and mimics: unveiling the potential of FDG-PET in guiding therapeutic approaches for neurodegenerative cognitive disorders

Abstract

Fluorodeoxyglucose F18 (FDG) positron emission tomography (PET) imaging can help clinicians pursue the differential diagnosis of various neurodegenerative diseases. It has become an invaluable diagnostic tool in routine clinical practice in conjunction with computed tomography (CT) imaging, magnetic resonance imaging (MRI), and biomarker studies. We present a single-institution case series and systematic literature review, showing how FDG-PET imaging has helped physicians diagnose neurodegenerative diseases and their mimickers and how patient care was amended. A single institution analysis and comprehensive literature search were completed following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. These medical subjects' headings (MeSH) terms were used: "FDG-PET" AND "dementia" OR "Alzheimer's" OR "neurodegeneration" OR "frontotemporal dementia" OR "atypical parkinsonian syndrome" OR "primary progressive aphasia" OR "lewy body dementia." The inclusion criteria included studies with uncertain diagnoses of neurocognitive disease resolved with FDG-PET, PET/MRI, or PET/CT hybrid imaging. A literature search resulted in 3,976 articles. After considering inclusion and exclusion criteria, 14 case reports and 1 case series were selected, representing 19 patients. The average age of patients was 70.8 years (range: 54-83 years). Five of the 19 patients were females. Dementia with Lewy bodies (DLB) had the highest propensity for being misidentified as another neurodegenerative disease, followed by Alzheimer's disease (AD) and frontotemporal dementia (FTD). Without accurate molecular imaging, neurodegenerative diseases may be missed or misdiagnosed. Our single-institution case series and literature review demonstrate how FDG-PET brain imaging can be used to correct and clarify preexisting clinical diagnoses of neurodegenerative disease.

Keywords: Alzheimer’s disease; FDG-PET; frontotemporal dementia; lewy body dementia; systematic review.

Figure 1

Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) schemata: diagrammatic representation of literature searches utilizing PubMed database.

Figure 2

Brain FDG-PET imaging: 3D stereotactic surface projection maps demonstrate moderate hypometabolism in the parietotemporal regions (right greater than left), which extends into the frontal lobes. There is accompanying mild hypometabolism in the precuneus and posterior cingulate gyri, especially on the right side, regions typically involved early in the setting of Alzheimer’s disease.

Figure 3

Brain FDG-PET imaging: 3D stereotactic surface projection maps demonstrate severe hypometabolism in the parietotemporal regions, left greater than right, with accompanying hypometabolism in the precuneus and posterior cingulate gyri bilaterally. There is extension of hypometabolism into the frontal lobes, indicating advanced neurodegenerative disease.

Figure 4

(A) Brain FDG-PET imaging: 3D stereotactic surface projection maps demonstrate mild to moderate hypometabolism in the bilateral parietotemporal regions (slightly more pronounced on the left side), which extends into the frontal lobes. There is accompanying mild hypometabolism in the precuneus and posterior cingulate gyri, regions typically involved early in the setting of Alzheimer’s disease. (B) Second Brain FDG-PET imaging taken 18 months after the first showing improvement in metabolic deficits.

Figure 5

(A) Brain FDG-PET imaging: Three-dimensional stereotactic surface projection (SSP) maps demonstrate severe asymmetric hypometabolism in the left frontal lobe, particularly involving the left dorsolateral and fronto-insular region, including the left frontal operculum (pars opercularis and pars triangularis of the left inferior frontal gyrus, expected Broca’s area). There is accompanying crossed cerebellar diaschisis, with right greater than left cerebellar hypometabolism. (B) Second Brain FDG-PET imaging taken 12 months after the first showed similar hypometabolism distributions.