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Metabolic Reduction in the Posterior Cingulate Cortex in Very Early Alzheimer’S Disease

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Metabolic Reduction in the Posterior Cingulate Cortex in Very Early Alzheimer’S Disease Metabolic Reduction in the Posterior Cingulate Cortex in Very Early Alzheimer’s Disease Satoshi Minoshima, MD, PhD,* Bruno Giordani, PhD,t Stanley Berent, PhD,t$ Kirk A. Frey, MD, PhD,*$ Norman L. Foster, MD,$ and David E. Kuhl, MD* This study investigated cerebral glucose metabolism in very early Alzheimer’s disease, before a clinical diagnosis of probable Alzheimer’s disease is possible, using [ ‘8F]flu~r~de~xygluc~~epositron emission tomography. First, 66 patients with probable Alzheimer’s disease with a spectrum of dementia severity (Mini-Mental State Examination score, 0-23) were recruited and studied. Cortical metabolic activity was analyzed topographically using three-dimensional stereotactic surface projections. Regression analysis was performed for each brain pixel to predict metabolic patterns of very early disease. Predictions were tested prospectively in a group of 8 patients who complained only of memory impairment without general cognitive decline (Mini-Mental State Examination score, 25 Ifr 1) at the time of scanning but whose condition later progressed to probable Alzheimer’s disease. Both results were compared to cerebral metabolic activity in 22 age-similar normal control subjects. Prediction and analysis of actual patients consistently indicated marked metabolic reduction (21-22%) in the posterior cingulate cortex and cinguloparietal transitional area in patients with very early Alzheimer’s disease. Mean metabolic reduction in the posterior cingulate cortex was significantly greater than that in the lateral neocortices or parahippocampal cortex. The result suggests a functional importance for the posterior cingulate cortex in impairment of learning and memory, which is a feature of very early Alzheimer’s disease. Minoshima S, Giordani B, Berent S, Frey KA, Foster NL, Kuhl DE. Metabolic reduction in the posterior cingulate cortex in very early Alzheimer’s disease. Ann Neurol 1997;42:85-94 Energy metabolic abnormalities in the brain of patients Alzheimer’s disease [ 1 11, of comparable severity as that with Alzheimer’s disease have been investigated using in the parietotemporal association cortex. Metabolic re- in vivo imaging techniques such as positron emission duction in the posterior cingulate cortex coincides with tomography (PET). Earlier PET reports indicated focal the observation of severe neurodegeneration in moder- accentuation of metabolic reduction in the parietal and ate to severe Alzheimer’s disease reported in early liter- temporal cerebral cortices in addition to general global ature [12]. The metabolic abnormality in the posterior decline [1-5]. In contrast to the association cortices, cingulate cortex has been previously overlooked in im- energy metabolism in the primary cortices and subcor- aging analysis and was reported only occasionally [ 131. ,tical structures is preserved relatively when compared This seems to be in part due to the difficulty to appre- to that in the parietotemporal and frontal association ciate exactly the posterior cingulate cortex on two- cortices. Such structures include the primary sensorim- dimensional tomographic slices oriented parallel to the otor and visual cortices, striatum, thalamus, cerebel- conventional orbitomeatal plane. lum, and pons [2, 61. Although these findings may not Energy metabolic alteration in the parietal and tem- be specific to Alzheimer’s dementia [7, 81, the stereo- poral cortices, as measured by PET, may precede cer- typical feature of parietotemporal metabolic reduction tain cognitive symptoms in Alzheimer‘s disease [ 141 is recognized consistently and is of potential utility in and can be observed in asymptomatic subjects at risk the clinical diagnosis of Alzheimer’s disease [9, 101. for familial Alzheimer’s disease [15, 161. However, the In addition to neocortical abnormalities in Alzhei- time course of metabolic abnormalities observed in the met’s disease, recent topographical analysis of PET posterior cingulate cortex is largely unknown. Using a images found significant metabolic reduction in the PET topographical analysis technique [lo], a recent posterior cingulate cortex in patients with probable collaborative study demonstrated possible metabolic re- From the Departments of *Internal Medicine, ?Psychiatry, and Address correspondence to Dr Minoshima, Division of Nuclear $Neurology, The University of Michigan Medical School, Ann Ar- Medicine, Department of Internal Medicine, The University of bor, MI. Michigan, BlG412 University Hospital, Ann Arbor, MI 48103- Received Mar 25, 1996, and in revised form Nov 22. Accepted for 0028. publication Dec 18, 1996. Copyright 0 1997 by the American Neurological Association 85 duction in the posterior cingulate cortex in apolipopro- of memory impairment with no apparent loss in general cog- rein E type 4 homozygotes without- symptoms of de- nitive, behavioral, or functional status. The classification of mentia [ 171. Analysis of pathological changes in very memory impairment required normal mental status (MMSE early disease may provide a better understanding of the scores 2 24, CDR = 0.5) with memory performance falling primary disease processes without secondary or reactive one standard deviation below the normal reference, that is, a combination score of Wechsler Memory Scale (WMS) changes that may complicate the advanced stages of subtests IV (Logical Memory) and VII (Paired Associates chronic illness. In addition, such knowledge may help Learning) of 19 or less [21], andlor a score on the Benton develop more sensitive and specific diagnostic schemes. Visual Retention Test of 6 or lower [22]. Each patient un- Investigations based on neuropathological examina- derwent PET at the time of the initial evaluation and was tions, however, may not be able to address easily early followed clinically for at least 2 years. Eight of 23 patients disease processes because of the difficulty in obtaining satisfied the diagnostic criteria of probable Alzheimer’s dis- brain specimens from patients diagnosed to have a very ease during the follow-up period. The interval between the early stage of the disease. In vivo imaging potentially collection of scan data and the diagnosis of probable Alzhei- has advantages in such situations because of its nonin- mer’s disease averaged 23 months, ranging from 4 to 39 vasive nature. months. These patients included 5 men and 3 women with In this study, we investigated the topographical dis- an average age of 69 2 4.6 years and a range from 63 to 73 years. All women were postmenopausal, and 1 patient was on tribution of cerebral energy metabolic alterations in estrogen replacement prior to or immediately after the scan- Alzheimer’s disease, particularly at a very early stage. ning. At the time of PET, the mean MMSE score \vas 25 ? We examined cerebral metabolic PET data sets ob- 1.1, which declined to 20 t- 3.0 during the follow-up pe- tained from two different populations with Alzheimer’s riod. Despite a mild decline in general mental status, severe disease. First, we predicted a metabolic pattern of a learning and memory impairment was evident in these 8 pa- very early stage of the disease using regression analysis tients at the time of PET. For example, of a possible score of of cerebral metabolism and mental status test results in 23 on WMS subtest IV, patients scored 3.5 t 1.5 on im- probable Alzheimer’s disease patients with dementia of mediate recall and only 0.17 2 0.25 on 30-minute delayed various severities. Second, we confirmed the predicted recall. One patient died approximately 5 years after the ini- result in actual patients with very early Alzheimer’s dis- tial evaluation, and neuropathological examination including ease whose diagnosis was established later in a clinical silver, myelin, glial, and ubiquitin stains confirmed Alzhei- mer’s disease pathology without coexistent disorders. In the follow-up or at autopsy. following sections, these patients are referred to as having “very early Alzheimer’s disease.” Materials and Methods Twenty-two age-similar normal control subjects were re- Subjects cruited by advertising. This group included 7 men and 15 Sixty-six patients with probable Alzheimer’s disease were re- women with an average age of 64 I7.5 years and a range cruited from the Department of Neurology Cognitive Disor- from 52 to 76. The mean MMSE score was 28 2 1.0, rang- ders Clinic at The University of Michigan Medical Center ing from 26 to 30. The CDR was 0 in all subject-s. hetween 1989 and 1994. The recruitment was part of an ongoing, cross-sectional study of Alzheimer’s disease and in- tended to involve a spectrum of dementia severity. The clin- Cerebral Glucose Metabolic Measurement ical diagnosis of probable Alzheimer’s disease was based on Each patient underwent cerebral metabolic measurement us- National Institute of Neurological and Communicative Dis- ing PET. The protocol was approved by the Institutional Re- orders and Stroke-Alzheimer’s Disease and Related Disorders view Board of The University of Michigan Medical School. Association (NINCDS-ADRDA) criteria [IS]. The mean age Written informed consent was obtained from each subject. A of this group was 68 ? 7.3 (mean -C standard deviation), Siemens ECAT scanner (model 931108-12, CTI, Knoxville, and the range from 50 to 82 years. Thirty-one men and 35 TN), which collects 15 simultaneous slices with 6.75-mm women were included. Seventeen patients were confirmed to slice separation, was used. All patients were fasted for at least be postmenopausal by medical chart review. Two patients
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