Hypometabolism based on a cutoff point on the mini-mental state examination in Parkinson ’ s disease

Objective: The aim of the present study was to evaluate cortical hypometabolism of the F-18fluorodeoxyglucose positron emission tomography (FDG-PET) based on a diagnostic cutoff point of the mini-mental state examination (MMSE) in de novo PD.Methods: We recruited 24 PD patients and 15 healthy controls to analyze FDG-PET. We divided the patients into two groups by the diagnostic cutoff point of MMSE for diagnosing dementia, with scores of>25 vs. < 25. FDG-PET was processed using statistical parametric mapping (SPM) 8 running on Matlab 11. Results: Patients with a MMSE < 25 presented lower score in time orientation, serial sevens, language and pentagon copying of MMSE compared to patients with a MMSE >25. Compared to healthy controls, patients with a MMSE> 25 and < 25 showed a fronto-temporo-parietal hypometabolism, which was more extended in patients with a MMSE < 25. Difference in cortical hypometabolism between patients with a MMSE >25 and < 25 was found in the right inferior parietal lobule. Conclusions: In the comparison by cutoff point of MMSE (25/24), hypometabolism in the right inferior parietal lobule suggests that the posterior cortical deficit is the main region ofde novo PD with cognitive impairment. Hypometabolism of right inferior parietal lobule is related to the damage of cerebral networkin de novo PD. Neurology Asia 2016; 21(3) : 247 – 253 Address correspondence to: Sang Jin Kim, Department of Neurology, Inje University College of Medicine,75 Bokji-ro, Buanjin-gu, Busan 614-735, Korea. Tel: +82 51 890 6425; E-mail: jsk502@hotmail.com INTRODUCTION Cognitive impairments can occur even in newly diagnosed, early stages of Parkinson’s disease (PD). Frontal/executive dysfunction is known to be the main cognitive impairments of PD patients, which may be attributed to the disruption of the frontostriatal circuitry and is consistent with the anatomic model of basal ganglia thalamocortical circuits. However, there is still considerable controversy about the pattern of cognitive impairments in PD because some reports suggest posterior cortical deficitsbased on studies describing explicit memory impairment and visuospatial/constructional dysfunction in PD. F-fluorodeoxyglucose positron emission tomography (FDG-PET) has been used to assess regional cerebral glucose metabolism (rCMRglc) for the differentiation of the cognitive status of PD patients.Nondemented patients or those with mild cognitive impairment (MCI) due to PD usually show hypometabolism in the parieto-occipital cortices.However, hypometabolism of dementia in PD (PDD) tends to present in multiple and wide cortical areas, including the lateral frontal, posterior cingulate and parieto-temporo-occipital cortices. Despite its relative insensitivity to mild forms of cognitive impairment, the mini-mental state examination (MMSE) is the most popular primary diagnostic tool for identifying cognitively impaired PD or PDD. Some recent reports have suggested a cutoff point for cognitive impairment or dementia. The aim of this study is to analyze the patterns of hypometabolism between two groups divided by the cutoff point of MMSE for cognitive impairment.