Combined 18F-fluorodeoxyglucose positron emission tomography and event-related potentials study of the cognitive impairment mechanisms in Parkinson's disease.

This study aimed to analyze positron emission tomography with 18F-fluorodeoxyglucose data and event-related potentials in the Go/NoGo paradigm in patients with Parkinson's disease with and without cognitive impairment. In the group of cognitively impaired patients, glucose metabolism was decreased in the frontal, parietal, cingulate and posterior temporal cortex. Correlations were found between the cognitive scores and cerebral glucose metabolism in those areas. Event-related potentials analysis revealed a decrease in the amplitude of the late positive wave (P300 NoGo wave) in the group of cognitively impaired patients. The analysis revealed that decline in amplitude of P300 wave was accompanied by decreased glucose metabolism in several cortical areas associated with cognitive impairment in Parkinson's disease. Correlations of glucose metabolism in these areas with event-related potentials amplitude in the NoGo condition confirm the important role of executive functions disorders in the pathogenesis of cognitive impairment in Parkinson's disease.

[Cerebral metabolism in patients with cognitive disorders: a combined MRS and PET study]. / Tserebral'nyi metabolizm u bol'nykh s kognitivnymi rasstroistvami: kombinirovannoe issledovanie s primeneniem magnitno-rezonansnoi spektroskopii i pozitronno-émissionnoi tomografii.

AIM: Magnetic resonance spectroscopy (MRS) allows studying the content of many metabolites in neural tissue in vivo. There are numerous studies devoted to the MRS data analysis in Alzheimer's disease (AD), but their results are contradictory. Thus, it is rational to compare the data obtained with MRS and positron emission tomography (PET) with fluorodeoxyglucose (FDG), which allows evaluating the brain functional state. In this paper, the authors compared MRS data in AD and mild cognitive impairment (MCI) with the cerebral glucose metabolism changes according to FDG PET. MATERIAL AND METHODS: Multivoxel proton MRS of the supraventricular area was performed in patients with AD (n=16) and MCI (n=14). The following metabolites ratios were evaluated: NAA/Cr, Cho/Cr, NAA/Cho (NAA - N-acetylaspartate, Cr - creatine, Cho - choline). All patients underwent neurological examination, assessment of cognitive status and PET with FDG. RESULTS: A decrease in NAA/Cr and Cho/Cr ratios in the supraventricular white matter and medial cortex in both hemispheres was observed in AD patients. In the MCI group, NAA/Cr ratio were decreased only in left white matter adjusting to the parietal cortex. Positive correlations of NAA/Cr and Cho/Cr ratios with cognitive status, as well as the cerebral glucose metabolism rate according to the PET data in frontal, parietal, temporal and cingulate cortex were revealed. CONCLUSION: The decrease in the NAA/Cr ratio in the supraventricular white matter and the medial cortex in AD and the correlation of this index with the results of cognitive tests and cerebral glucose metabolism suggest that it can be of diagnostic significance, reflecting the severity of cognitive impairment. In this case, the NAA/Cr ratio should be evaluated taking into account the changes in concentrations of both metabolites (NAA and Cr) in dementia.

[Characteristics of cerebral glucose metabolism in patients with cognitive impairment in Parkinson's disease]. / Osobennosti tserebral'nogo metabolizma gliukozy u bol'nykh s kognitivnymi narusheniiami pri bolezni Parkinsona.

AIM: To study the relationship between early cognitive impairment symptoms and cerebral glucose metabolism in different brain regions (according to the positron emission tomography (PET) data) in Parkinson's disease (PD) in order to increase the diagnostic and treatment efficacy. MATERIAL AND METHODS: Two groups of patients with PD (stage I-III), including 11 patients without cognitive disorders and 13 with mild cognitive impairment (MCI), were examined. The control group included 10 age-matched people with normal cognition. To evaluate cognitive state, the Mini mental state examination (MMSE), the Frontal assessment battery (FAB) and the 'clock drawing test' were used. The regional cerebral glucose metabolism rate (CMRglu) was assessed using PET with 18F-fluorodeoxyglucose (FDG). RESULTS AND CONCLUSION: In PD patients, CMRglu were decreased in the frontal (Brodmann areas (BA) 9, 10, 11, 46, 47), occipital (BA 19) and parietal (BA 39), temporal (BA 20, 37), and cingulate cortex (BA 32) compared to the control group. Cerebral glucose metabolism was decreased in the frontal (BA 8, 9, 10, 45, 46, 47), parietal (BA 7, 39, 40) and cingulate cortex (BA 23, 24, 31, 32) in the group of PD patients with MCI compared to PD patients with normal cognition. Hypometabolism in BA 7, 8, 23, 24, 31, 40 was revealed only in comparison of PD and PD-MCI groups, and did not appear in case of comparison of cognitively normal PD patients with the control group. It is possible to suggest that the mentioned above brain areas were associated with cognitive impairment. The revealed glucose hypometabolism pattern possibly has the diagnostic value for the early and preclinical diagnosis of MCI in PD and control of treatment efficacy.