Occipital Glucose Metabolism in Dementia with Lewy Bodies with and without Parkinsonism: A Study Using Positron Emission Tomography

Reduction of glucose metabolism in the occipital lobe is reported in dementia with Lewy bodies (DLB) and Parkinson's disease. If dysfunction of the nigrostriatal system is responsible for occipital hypometabolism, (1) DLB patients with parkinsonism would show a lower occipital metabolism than do patients without parkinsonism, and (2) DLB patients without parkinsonism would show an occipital metabolism comparable to those of normal subjects and patients with Alzheimer's disease (AD). To examine these hypotheses, we studied the regional cerebral metabolic rate of glucose (rCMRglc) in patients with a clinical diagnosis of DLB or AD, using (18)F-fluorodeoxyglucose and positron emission tomography. The subjects consisted of 15 DLB patients with parkinsonism, 7 DLB patients without parkinsonism and 7 AD patients without parkinsonism. The medial and lateral occipital rCMRglc was significantly lower in the DLB patients without parkinsonism than in the AD patients. There were no significant differences in occipital metabolic rates between the DLB groups with and without parkinsonism. DLB patients without parkinsonism showed a significant reduction of occipital glucose metabolism which is comparable with that of DLB patients with parkinsonism. The neurobiological bases of occipital hypometabolism in DLB may be pathological processes in the brainstem or basal forebrain structures other than the nigrostriatal system.