Tapping deficits are evident throughout manifest and premanifest stages. Deficits are more pronounced in later stages and correlate with clinical scores as well as regional brain atrophy, which implies a link between structure and function. The ability to track motor phenotype progression with force-transducer-based tapping measures will be tested prospectively in the TRACK-HD study.
Objectives: To evaluate in vivo brain metabolite differences in control subjects, individuals with premanifest Huntington disease (pre-HD), and individuals with early HD using 1 H magnetic resonance spectroscopy (MRS) and to assess their relationship with motor performance.Methods: Eighty-five participants (30 controls, 25 pre-HD, and 30 early HD) were recruited as part of the TRACK-HD study. Eighty-four were scanned at 3 T with single-voxel spectroscopy in the left putamen. Disease burden score was Ͼ220 among pre-HD individuals. Subjects underwent TRACK-HD motor assessment including Unified Huntington's Disease Rating Scale (UHDRS) motor scoring and a novel quantitative motor battery. Statistical analyses included linear regression and one-way analysis of variance.
Results:Total N-acetylaspartate (tNAA), a neuronal integrity marker, was lower in early HD (ϳ15%) vs controls (p Ͻ 0.001). N-acetylaspartate (NAA), a constituent of tNAA, was lower in pre-HD (ϳ8%) and early HD (ϳ17%) vs controls (p Ͻ 0.05). The glial cell marker, myo-inositol (mI), was 50% higher in early HD vs pre-HD (p Ͻ 0.01). In early HD, mI correlated with UHDRS motor score (R 2 ϭ 0.23, p Ͻ 0.05). Across pre-HD and early HD, tNAA correlated with performance on a tongue pressure task (R 2 ϭ 0.30, p Ͻ 0.0001) and with disease burden score (R 2 ϭ 0.17, p Ͻ 0.005).
Conclusions:We demonstrate lower putaminal tNAA in early HD compared to controls in a crosssection of subjects. A novel biomarker role for mI in early HD was also identified. These findings resolve disagreement in the literature about the role of MRS as an HD biomarker. We conclude that putaminal MRS measurements of NAA and mI are promising potential biomarkers of HD onset and progression. Neurology ® 2010;75:1702-1710 GLOSSARY AD ϭ Alzheimer disease; Cr ϭ creatine; DBS ϭ disease burden score; Glu ϭ glutamate; GPC ϭ glycerophosphocholine; HD ϭ Huntington disease; mI ϭ myo-inositol; MR ϭ magnetic resonance; MRS ϭ 1 H magnetic resonance spectroscopy; NAA ϭ N-acetylaspartate; NAAG ϭ N-acetylaspartylglutamate; PC ϭ phosphocholine; PCr ϭ phosphocreatine; pre-HD ϭ premanifest Huntington disease; SNR ϭ signal-to-noise ratio; tCho ϭ total choline; tCr ϭ total creatine; TE ϭ echo time; tNAA ϭ total N-acetylaspartate; TR ϭ repetition time; UBC ϭ University of British Columbia; UHDRS ϭ Unified Huntington's Disease Rating Scale; VBM ϭ voxel-based morphometry.The eventual development of Huntington disease (HD) symptoms can be predicted through detection of CAG trinucleotide repeat expansion in the HTT gene 1 in premanifest gene carriers. However, definitive HD biomarkers, able to objectively identify disease onset and progression, are lacking. Evaluation of potential biomarkers are the focus of longitudinal studies such as TRACK-HD 2 and PREDICT-HD. H magnetic resonance spectroscopy (MRS) has previously been evaluated as a biomarker modality in premanifest and early HD. [4][5][6][7][8][9][10][11] However, the literature is conflicted with regard to the utility of metabolites such as total N-ac...
Huntington disease (HD) is a dominantly inherited neurodegenerative disorder that usually presents in adulthood with characteristic motor and cognitive features and with variable and diverse psychiatric disturbances. Following the discovery of the causative defect in the HTT gene in 1993, great advances in understanding the pathogenesis of HD have been made, yet no effective disease-modifying therapy has been identified. In this new era of HD research, we have seen the emergence of a number of large clinical trials, the systematic search for novel biomarkers and the recent initiation of the first pre-manifest HD clinical studies. In this review, we seek to provide an overview of the clinical and genetic features of HD together with a summary of clinical research at this time.
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