Clinical study on metabolic differences in the limbic system between non-demented Parkinson's disease patients and Parkinson's disease dementia patients.

BACKGROUND: Parkinson's disease (PD) is a neurodegenerative disorder that affects millions of people worldwide. PD is widely known for its motor symptoms and non-motor symptoms. The long-term clinical course of PD is complicated by the onset of dementia in 80 % of patients. The diagnosis of PD is based on the patient's medical history and clinical examination, but molecular imaging can play an important role in the study of disease progression and mechanisms. [18F] -fluorodeoxyglucose (FDG) -PET, as one of the important molecular imaging methods, was adopted by our research to compare the differences in brain metabolism between PD patients with normal cognition (PD-NC) and PD with dementia (PDD), as well as healthy control (HC).Thereby, utilizing FDG-PET imaging technology to detect Parkinson's disease dementia at an early stage, enabling early prevention of cognitive impairment, slowing disease progression, and enhancing patient quality of life.

METHOD: Thirty-seven PD patients and 15 healthy controls (HCs) who visited the Department of Neurology of China-Japan Union Hospital of Jilin University were included in this study. According to the diagnostic criteria for cognitive dysfunction in Parkinson's disease, PD patients were divided into the normal cognition group (PD-NC) and the dementia group (PDD). Each subject underwent 18F-FDG PET examination. The glucose metabolism of brain regions in the three groups was compared. Further, taking the limbic system as the region of interest (ROI), the glucose metabolism of ROIs in the three groups of subjects was further compared.

RESULTS: After normalizing whole-brain metabolism, PD-NC patients showed reduced metabolism in the limbic system (hippocampus, caudate gyrus, inferior temporal gyrus, insular lobe), fusiform gyrus, parietal lobe (precuneus, angular, supramarginal gyrus), frontal lobe (rectus gyrus) compared to HC. PDD patients showed significantly reduced metabolism in the frontal lobe (middle frontal gyrus, rectus gyrus) and temporal lobe (middle temporal gyrus, inferior temporal gyrus) compared to HC, and also showed reduced metabolism in the precuneus and angular gyrus compared to PD-NC patients. However, PDD patients showed increased metabolism in the cerebellum, amygdala and putamen compared to HC, and showed increased metabolism in cerebellum and amygdala compared to PD-NC patients. After normalizing metabolism of ROIs, PDD patients showed increased metabolism in the bilateral amygdala (max voxel cluster, peak T-value) compared to both PD-NC patients and HC, while showed significant reduced metabolism in the right rectus gyrus and the middle of the right cingulate gyrus compared to HC. And PD-NC patients showed significant reduced metabolism in the right rectus gyrus and right insular lobe compared to HC.

CONCLUSION: The hypometabolism distribute for PD-NC mainly related to the following functional impairments: emotion perception/ processing/ regulation/ recognition, control of autonomous attention diversion, episodic memory retrieval, personal identity and past experiences, which usually occurred in the early stage of PD. With the progression of the PD disease course, taking the limbic system as the ROIs, PDD patients had decreased metabolism in the rectal gyrus and cingulate gyrus, which might be the result of cognition dysfunction/ emotion disorder/ attention deficits. And PDD patients usually had enhanced metabolism in the amygdala which might be due to the activation of glial cells caused by chronic inflammatory responses.