A Comparative study of Posterior cingulate metabolism in Patients with Mild Cognitive Impairment due to Parkinson’s Disease or to Alzheimer’s Disease

Abstract

Few comparative studies exist of metabolic brain changes in cognitive impairment among neurodegenerative illnesses. In this study, we compared posterior cingulate (PCC) metabolic abnormalities in patients with mild cognitive impairment (MCI) due to Parkinson’s disease (PD) and to Alzheimer’s disease (AD) as measured by proton magnetic resonance spectroscopy (1H-MRS). Thirty eight patients with idiopathic PD, including 20 patients with mild cognitive impairment (PDMCI), 18 patients with normal cognitive (PDN), 18 patients with probable mild cognitive impairment (ADMCI), and 25 healthy older controls (HC) underwent PCC 1H-MRS scans. Compared with controls, patients with PDMCI exhibited significantly reduced concentration of N-acetyl aspartate (NAA) and total Creatine (tCr), while patients with ADMCI exhibited significantly increased concentration of myo-inositol (Ins), and reduced NAA/Ins ratio. There was reduced concentration of NAA, Ins and tCr in PDMCI compared with ADMCI. No significant metabolic alteration was found in PDN subjects. Besides, ROC analysis revealed that the concentration of tCr could differentiate PDMCI from PDN with an AUC of 0.71, and the level of NAA/Ins ratio could differentiate subjects with MCI from normal cognitive controls with an AUC of 0.74. Patients with PDMCI and ADMCI exhibited distinct PCC metabolic 1H-MRS profiles. Findings suggest that cognitively normal PD patients with low NAA, tCr in the PCC might be at risk of preclinical PDMCI, and also the Ins and/or NAA/MI ratio in the PCC should be reconsidered as a possible biomarker of preclinical MCI in clinical practice. So, comparison of PCC 1H-MRS profiles of cognitive impairment among neurodegenerative illnesses may provide useful information for better defining the disease process and elucidate possible treatment mechanisms.