title: Posterior parietooccipital hypometabolism may differentiate mild cognitive impairment from dementia in Parkinson's disease.
abstract: OBJECTIVE
  Patients with Parkinson's disease (PD) may have normal cognition, mild cognitive impairment (MCI) or dementia. We investigated differences in cerebral metabolism associated with these three cognitive states and the relationship between metabolism and cognitive dysfunction.
  
  
  METHODS
  FDG PET and a battery of neuropsychological tests were used to study PD patients with dementia (n = 19), MCI (n = 28) and normal cognition (n = 21), and control subjects (n = 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 metabolism 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 function with metabolism in the parietooccipitotemporal junction and frontal lobe, memory with temporoparietal metabolism, visuospatial function with occipitoparietal and temporal metabolism, and language with frontal metabolism.
  
  
  CONCLUSIONS
  PD patients with MCI exhibited hypometabolism in several cortical regions compared with controls, and in the frontal and parietal regions compared with cognitively normal patients. Hypometabolism was higher in patients with dementia than in those with MCI, mainly in the posterior cortical areas where it was correlated with visuospatial, memory and executive functions.
authors.affiliation: Neurosciences Area, CIMA, Department of Neurology and Neurosurgery, Clinica Universidad de Navarra, University of Navarra, Pamplona, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Garcia-Garcia
authors.forename: Pedro
authors.initials: P
authors.lastname: Clavero
authors.forename: Carmen
authors.initials: C
authors.lastname: Gasca Salas
authors.forename: Isabel
authors.initials: I
authors.lastname: Lamet
authors.forename: Javier
authors.initials: J
authors.lastname: Arbizu
authors.forename: Rafael
authors.initials: R
authors.lastname: Gonzalez-Redondo
authors.forename: Jose A
authors.initials: JA
authors.lastname: Obeso
authors.forename: Maria C
authors.initials: MC
authors.lastname: Rodriguez-Oroz
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D060825:Cognitive Dysfunction / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000378:metabolism*; D003704:Dementia / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000378:metabolism*; D003937:Diagnosis, Differential; D005260:Female; D019788:Fluorodeoxyglucose F18; D005947:Glucose / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D009778:Occipital Lobe / Q000000981:diagnostic imaging / Q000378:metabolism*; D010296:Parietal Lobe / Q000000981:diagnostic imaging / Q000378:metabolism*; D010300:Parkinson Disease / Q000000981:diagnostic imaging / Q000378:metabolism*; D049268:Positron-Emission Tomography; D014057:Tomography, X-Ray Computed
chemical_list: D019788:Fluorodeoxyglucose F18; D005947:Glucose