Apparent Relative Hypermetabolism of Selective Brain Areas in Huntington Disease and Importance of Reference Region for Analysis

Abstract

Purpose: We investigated the pattern of reduced and increased metabolism in symptomatic Huntington chorea (HD) patients and assessed the influence of intensity normalization method. Patients and Methods: FDG brain PET was performed in 11 manifest HD patients and 11 age-matched controls. Images underwent statistical parametric mapping analysis after global normalization or with white matter or pons as reference region. Region of interest analysis of FDG uptake ratios was also performed using total region or white matter as reference. Correlation between regional uptake ratios to that of the caudate was evaluated by linear regression analysis. Results: Although statistical parametric mapping analysis identified striatal hypometabolism and thalamic hypermetabolism in HD patients with all methods, substantially different FDG uptake patterns were shown depending on the method of intensity normalization. Global normalization displayed large areas of relative normalized hypermetabolism across the cerebral cortex and cerebellum. With white matter as reference, relative normalized hypermetabolism was observed in the thalamus and a much more limited area of the cortex. With pons as reference, relative normalized hypermetabolism was largely confined to the thalamus and a small area of the cerebellum. Conclusion: These results demonstrate apparent relative normalized hyper-metabolism in selective brain regions in manifest HD patients. Furthermore, the choice of reference region for intensity normalization is critical for accurate monitoring of this metabolic change with FDG PET.