Quantitative 7T phase imaging in premanifest Huntington disease.

BACKGROUND AND PURPOSE: In vivo MR imaging and postmortem neuropathologic studies have demonstrated elevated iron concentration and atrophy within the striatum of patients with Huntington disease, implicating neuronal loss and iron accumulation in the pathogenesis of this neurodegenerative disorder. We used 7T MR imaging to determine whether quantitative phase, a measurement that reflects both iron content and tissue microstructure, is altered in subjects with premanifest Huntington disease. MATERIALS AND METHODS: Local field shift, calculated from 7T MR phase images, was quantified in 13 subjects with premanifest Huntington disease and 13 age- and sex-matched controls. All participants underwent 3T and 7T MR imaging, including volumetric T1 and 7T gradient recalled-echo sequences. Local field shift maps were created from 7T phase data and registered to caudate ROIs automatically parcellated from the 3T T1 images. Huntington disease-specific disease burden and neurocognitive and motor evaluations were also performed and compared with local field shift. RESULTS: Subjects with premanifest Huntington disease had smaller caudate volume and higher local field shift than controls. A significant correlation between these measurements was not detected, and prediction accuracy for disease state improved with inclusion of both variables. A positive correlation between local field shift and genetic disease burden was also found, and there was a trend toward significant correlations between local field shift and neurocognitive tests of working memory and executive function. CONCLUSIONS: Subjects with premanifest Huntington disease exhibit differences in 7T MR imaging phase within the caudate nuclei that correlate with genetic disease burden and trend with neurocognitive assessments. Ultra-high-field MR imaging of quantitative phase may be a useful approach for monitoring neurodegeneration in premanifest Huntington disease.

Changes in the thalamus in atypical parkinsonism detected using shape analysis and diffusion tensor imaging.

BACKGROUND AND PURPOSE: The thalamus is interconnected with the nigrostriatal system and cerebral cortex and has a major role in cognitive function and sensorimotor integration. The purpose of this study was to determine how regional involvement of the thalamus differs among Parkinson disease, progressive supranuclear palsy, and corticobasal syndrome. MATERIALS AND METHODS: Nine patients with Parkinson disease, 5 with progressive supranuclear palsy, and 6 with corticobasal syndrome underwent 3T MR imaging along with 12 matched, asymptomatic volunteers by using a protocol that included volumetric T1 and diffusion tensor imaging. Acquired data were automatically processed to delineate the margins of the motor and nonmotor thalamic nuclear groups, and measurements of ADC were calculated from the DTI data within these regions. Thalamic volume, shape, and ADC were compared across groups. RESULTS: Thalamic volume was smaller in the progressive supranuclear palsy and corticobasal syndrome groups compared with the Parkinson disease and control groups. Shape analysis revealed that this was mainly due to the diminished size of the lateral thalamus. Overall, ADC measurements were higher in the progressive supranuclear palsy group compared with both the Parkinson disease and control groups, and anatomic subgroup analysis demonstrated that these changes were greater within the motor regions of the thalamus in progressive supranuclear palsy and corticobasal degeneration. CONCLUSIONS: Reduced size and increased ADC disproportionately involve the lateral thalamus in progressive supranuclear palsy and corticobasal syndrome, consistent with selective neurodegeneration and atrophy in this region. Because these findings were not observed in Parkinson disease, they may be more specific markers of tau-related neurodegeneration.