Fluoro-2-deoxy-d-glucose-PET measures may improve prediction of the conversion to Alzheimer disease, especially in combination with the APOE genotype.

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Objectives: Declines in brain glucose metabolism have been described early in Alzheimer's disease (AD), and there is evidence that a genetic predisposition to AD contributes to accelerate this process. The epsilon4 (e4) allele of the apolipoprotein E (ApoE) gene has been implicated as a major risk factor in this process. The aim of this FDG-PET study was to assess the ApoE e4 dose related effect on regional cerebral glucose metabolism (METglc) in clinical AD patients, with statistical voxel based methods. Methods: Eighty six consecutive mild to moderate AD patients included in the Network for Efficiency and Standardisation of Dementia Diagnosis database underwent FDG-PET scans at rest. PCR was used to determine the ApoE genotype. Patients were grouped as e4 non-carriers (n = 46), e3/e4 (n = 27) and e4/ e4 (n = 13) carriers. A voxel-based mapping program was used to compare each AD subgroup with a database of 35 sex and age matched controls (p,0.001, corrected for cluster extent) and also to compare between the subgroups (p,0.001, uncorrected). Results: No difference was found as to age at examination, age at onset, sex, disease duration, educational level, or severity of dementia between AD subgroups. Compared with controls, all AD subgroups had equivalent METglc reductions in the precuneus, posterior cingulate, parietotemporal, and frontal regions. Direct comparisons between AD subgroups indicated that patients with at least one e4 allele had METglc reductions within additional associative and limbic areas compared with e4 noncarriers.Conclusions: The present FDG-PET study showed different metabolic phenotypes related to the ApoE genotype in clinical AD patients, as revealed with voxel based statistical methods. The results suggest a generalised disorder in e4 carriers impairing metabolism globally, in addition to the more localised changes typical of AD patients.

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Background: Clinically apparent Alzheimer's disease (AD) is thought to result when brain tissue damage exceeds a critical threshold of ''brain reserve'', a process possibly accelerated by the apolipoprotein E (ApoE) E4 allele. The interaction between onset age and ApoE genotype was investigated to assess whether early disease onset (,65 years) in patients carrying the E4 allele is associated with greater cerebral metabolic (regional cerebral metabolic rate of glucose utilisation, rCMRgl) reduction. Methods: AD patients, divided into early (EOAD; 27 patients) and late onset (LOAD; 65 patients) groups, both groups balanced as to the number of E4 carriers (E4+) and non-carriers (E42), and matched controls (NC; 35 cases) underwent 18 F-FDG PET ([ 18 F]fluorodeoxyglucose positron emission tomography) scanning. SPM'99 software was used to compare AD patients to NC and to perform a two way ANOVA with onset age and ApoE genotype as grouping factors. Results were considered significant at p,0.001, uncorrected. Results: AD patients demonstrated rCMRgl reductions compared to NC, with rCMRgl lower in association cortex and relatively higher in limbic areas in EOAD compared to LOAD subjects. rCMRgl was lower in the anterior cingulate and frontal cortex for E4+ compared to E42 subjects. A significant onset age by ApoE interaction was detected in the hippocampi and basal frontal cortex, with EOAD E4+ subjects having the greatest rCMRgl reduction. Conclusions: The interactive effects of early onset age, possibly reflecting lower brain reserve, and ApoE E4 allele, possibly leading to greater tissue damage, lead to reduced tolerance to the pathophysiological effects of AD in key brain regions.

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We describe and present a videotape of a 57-year-old woman admitted to our Neurological Clinic at 46 years of age due to extrapyramidal manifestations suggesting Parkinson's disease (PD) and with a brain magnetic resonance imaging scan showing multi-infarctual leukoencephalopathy. Various investigations led to the diagnosis of Anderson Fabry's disease (AFD). We discuss the possibility of correlation between the patient's parkinsonism and AFD.