P2-180: Regional cerebral metabolic differences of mild cognitive impairment (MCI) by delayed recall impairment degree

Abstract

Mild cognitive impairment (MCI) is one of the widely used concepts indicative of the transitional cognitive condition between normal aging and dementia. However, there have been no standardized indices defining memory impairment of MCI. This study was to elucidate the cerebral metabolic differences between MCI groups divided by the degree of delayed recall impairment. All candidates were examined by neuropsychiatrists according to the protocol of the Korean Version of the Consortium to Establish a Registry for Alzheimer's Disease Assessment Packet (CERAD–K). They also underwent [18F] fluoro–deoxyglucose positron emission tomography (18F–FDG PET) scan. 63 right–handed MCI (Total MCI; T–MCI) patients were recruited by diagnostic criteria, which were cognitive impairment necessarily including memory impairment; essentially preserved general cognitive function; largely intact functional activities; not demented. Among them 55 MCI patients over 60 years were divided into two subgroups according to the presence of impairment in any of two delayed recall measures in the CERAD–K neuropsychological battery: 20 MCI patients with impaired delayed recall (DR+MCI); and 35 MCI patients with intact delayed recall (DR–MCI). Delayed recall impairment is performance of 1.5 or more SDs below the age, sex, and education norm on CERAD Word list recall or Constructional recall test. 25 healthy control subjects (NC) were recruited. The differences in the regional cerebral glucose metabolic rate between each MCI and NC group were tested on a voxel–by–voxel basis using the Statistical Parametric Mapping (SPM) 99 software (p < 0.05, corrected). Compared to the NC subjects, the bilateral posterior cingulate cortex (PCC) and right splenium of cingulum in T–MCI patients showed hypometabolism. DR+MCI patients showed hypometabolism in the bilateral PCC and right splenium of cigulum, while the right splenium of cingulum in DR–MCI patients showed decreased metabolism compared to NC. Additionally, compared to DR–MCI patients, DR+MCI patients showed a hypometabolic trend in right parahippocampal gyrus (p < 0.001, uncorrected). These investigations generally have emphasized that brain functional differences were found according to the degree of delayed recall impairment in MCI which may prove useful for clinicians in early detection and determining the diagnostic index of MCI.