Differential regional cerebral glucose metabolism in clinical syndromes of frontotemporal lobar degeneration: a study with FDG PET

Frontotemporal lobar degeneration( FTLD) is the third most common dementia, following Alzheimer's disease and Lewy body disease. Four prototypic neurobehavioral syndromes can be produced by FTLD: frontotemporal dementia (FTD), frontotemporal dementia with motor neuron disease (MND), semantic dementia (SD), and progressive aphasia (PA). We investigated patterns of metabolic impairment in patient with FTLD presented with four different clinical syndromes. We analysed glucose metabolic patterns on FDG PET images obtained from 34 patients with a clinical diagnosis of FTLD (19 FTD, 6 MND, 6 SD, and 3 PA, according to a consensus criteria for clinical syndromes associated with FTLD) and 7 age-matched healthy controls using SPM99. Patients with FTD had metabolic deficit in the left frontal cortex and bilateral anterior temporal cortex. Hypometabolism in the bilateral premotor are was shown in patients with MND. Patients with SD had metabolic deficit in the left posterior temporal cortex including Wernicke's area, while hypometabolism in the bilateral inferior frontal gyrus including Broca's area and left angular gyrus was seen in patients with PA. These metabolic patterns were well correlated with clinical features of FTLD syndromes. These data provide a biochemical basis of clinical classification of FTLD. FDG PET may help evaluate and classify patients with FTLD