The Diagnostic Role of FDG-PET in Dementias Presenting with Language and Behavioral Symptom.

OBJECTIVE: This study aimed to assess the diagnostic contribution of Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) in neurodegenerative dementias presenting with language-predominant symptoms, with or without accompanying behavioral changes, and to evaluate the correspondence between PET-derived metabolic patterns and cerebrospinal fluid (CSF) biomarkers. METHODS: Sixteen patients with language-predominant onset were categorized into two groups: Alzheimer’s disease (AD) spectrum (n=8) and the frontotemporal lobar degeneration (FTLD) spectrum (n=8). All participants underwent clinical evaluation, neuropsychological testing, and FDG-PET imaging. Cerebrospinal fluid biomarkers [Amyloid Beta (Aβ42), total tau, and phosphorylated tau] were analyzed in eligible individuals (n=6). The two groups were compared across demographic, clinical, and neuroimaging parameters. RESULTS: FDG-PET revealed pronounced posterior temporoparietal hypometabolism in AD-spectrum patients, whereas FTLD-spectrum patients demonstrated frontal, insular, and anterior temporal metabolic involvement. Cerebrospinal fluid biomarker profiles consistently supported Alzheimer-type pathology among AD-spectrum cases. In the FTLD group, one patient exhibited borderline-low Aβ42; however, the corresponding FDG-PET pattern was characteristic of FTLD. CONCLUSION: FDG-PET demonstrates a supportive role in differentiating AD from FTLD among patients presenting with language-predominant neurodegenerative syndromes. In scenarios where CSF biomarkers are unavailable or yield borderline values, FDG-PET-based metabolic signatures may offer additional guidance and can contribute to strengthening multimodal diagnostic frameworks in geropsychiatry settings.