Regional cerebral glucose metabolism in dementia with lewy bodies and Alzheimer's disease

Objective: To delineate the features of regional cerebral metabolic rate of glucose (CMRglc) in dementia with Lewy bodies (DLB). Methods: We compared absolute CMRglc in 12 patients with a clinical diagnosis of DLB, 12 patients with a clinical diagnosis of Alzheimer's disease (AD), and 12 normal volunteers (NC), using ¹⁸F-fluorodeoxyglucose (FDG) and PET. The three groups were matched for age and sex, and there were no differences in disease duration or severity of cognitive disturbances between the DLB and AD groups. Results: CMRglc was significantly lower in patients with DLB than in that of NC in most parts of the brain, except the sensorimotor cortices, basal ganglia, thalamus, and pons. Between the DLB and AD groups, there were significant regional CMRglc differences in the medial and lateral occipital lobes. In DLB and AD, the CMRglc reduction patterns were similar, though the global metabolic reduction was larger in DLB, and the occipital CMRglc reduction in DLB could differentiate DLB from AD. The relative occipital CMRglc (normalized to the sensorimotor CMRglc) was a useful measure for the differential diagnosis of DLB from AD. The sensitivity and the specificity were 92% when using the minimal value of the normalized occipital CMRglc in the NC group as the cut-off point. Conclusion: These different regional CMRglc reductions substantiate the pathologic, neurochemical, and clinical differences between DLB and AD.