ORIGINAL ARTICLE Posterior parietooccipital hypometabolism may differentiate mild cognitive impairment from dementia in Parkinson’ s disease David Garcia-Garcia & Pedro Clavero & Carmen Gasca Salas & Isabel Lamet & Javier Arbizu & Rafael Gonzalez- Redondo & Jose A. Obeso & Maria C. Rodriguez-Oroz Received: 24 March 2012 / Accepted: 13 July 2012 / Published online: 8 August 2012 # Springer-Verlag 2012 Abstract Purpose Patients with Parkinson’s disease (PD) may have normal cognition, mild cognitive impairment (MCI) or dementia. We investigated differences in cere- bral metabolism associated with these three cognitive states and the relationship between metabolism and cog- nitive dysfunction. Methods FDG PET and a battery of neuropsychological tests were used to study PD patients with dementia (n 0 19), MCI (n 0 28) and normal cognition (n 0 21), and control subjects (n 0 20). Regional glucose metabolism in patients and controls was analysed using statistical parametric mapping (SPM8) corrected for age, motor severity and depression. Correlations between the mini-mental state examination score and Z-score values of the different cognitive domains with respect to cerebral FDG uptake were assessed using SPM8. Results PD patients with MCI (PD-MCI patients) exhibited decreased FDG uptake in the frontal lobe, and to a lesser extent in parietal areas compared with cognitively normal patients. Patients with dementia showed reduced metabo- lism in the parietal, occipital and temporal areas and a less extensive reduction in the frontal lobe compared with PD- MCI patients, while widespread hypometabolism was seen in comparison with patients with normal cognition. PD-MCI patients exhibited reduced FDG uptake in the parietal and occipital lobes and in localized areas of the frontal and temporal lobes compared with controls, whereas patients with dementia showed a widespread reduction of cortical metabolism. Mini-mental state examination score correlated positively with metabolism in several lobes, executive func- tion with metabolism in the parietooccipitotemporal junction and frontal lobe, memory with temporoparietal metabolism, David Garcia-Garcia and Pedro Clavero contributed equally to this work. Electronic supplementary material The online version of this article (doi:10.1007/s00259-012-2198-5) contains supplementary material, which is available to authorized users. D. Garcia-Garcia : P. Clavero : C. Gasca Salas : I. Lamet : R. Gonzalez-Redondo : J. A. Obeso : M. C. Rodriguez-Oroz Neurosciences Area, CIMA, Department of Neurology and Neurosurgery, Clinica Universidad de Navarra, University of Navarra, Pamplona, Spain D. Garcia-Garcia : C. Gasca Salas : R. Gonzalez-Redondo : J. A. Obeso : M. C. Rodriguez-Oroz Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain J. Arbizu Department of Nuclear Medicine, Clínica, University of Navarra, Pamplona, Spain M. C. Rodriguez-Oroz Ikerbasque, Basque Foundation for Science, Bilbao, Spain Present Address: M. C. Rodriguez-Oroz (*) Department of Neurology and Neuroscience, University Hospital Donostia, BioDonostia Research Institute, San Sebastian, Spain e-mail: maria.rodriguezoroz@biodonostia.org Eur J Nucl Med Mol Imaging (2012) 39:1767–1777 DOI 10.1007/s00259-012-2198-5