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A B S T R A C TThe aim of the study is to analyze diffusion tensor imaging (DTI) characteristics of the Guillain-Mollaret triangle (GMT) in patients with hypertrophic olivary degeneration (HOD) and to investigate their correlation with previously reported histopathology. DTI was performed in 10 patients diagnosed with HOD. Fractional anisotropy, apparent diffusion coefficient, axial diffusivity, and radial diffusivity were measured in the inferior olivary nucleus (IO), the central tegmental tract, the red and the dentate nuclei, and the superior cerebellar peduncle of HOD patients and compared to age, sex, and side-matched 10 neurologically normal population. The prominent finding on DTI in affected IO was an increase in radial diffusivity compatible with demyelination. While conventional magnetic resonance imaging did not show any sign of involvement in the other components of GMT, DTI demonstrated signal changes in all anatomical components of the GMT. Main DTI findings in GMT of patients with HOD were an increase in radial diffusivity representing demyelination and an increase in axial diffusivity that is reflective of neuronal hypertrophy. DTI parameters can reflect the spatiotemporal evolution of transneuronal degeneration associated with HOD in a manner consistent with the known pathologic stages of HOD.

During the process of developing the DSM-5, a new phenotype of ADHD was proposed-the ADHD restrictive inattentive presentation (ADHD-RI), describing subjects with high endorsement of inattentive symptoms and a low level of hyperactivity. However, this phenotype was not included in the DSM-5 because of the lack of robust neurobiological data. We aimed to assess the specific neurobiological underpinnings of individuals presenting ADHD-RI. We compared a sample of 301 subjects (101 ADHD-Combined; 50 ADHD-RI; 50 ADHD predominantly inattentive type and 100 typically developing subjects) aged 8-15 years, using a complete neuropsychological battery, molecular genetic data (DRD4 and DAT1 most studied polymorphisms) and functional MRI during a Go-No/Go task. Subjects with ADHD-RI had a significantly different neuropsychological profile compared with the other groups, including lower psychomotor speeds, longer reaction times and the worst overall performance in the global neurocognitive index. The proportion of subjects with the presence of DRD4-7 repeat allele was significantly higher in ADHD-RI. The fMRI data suggested that more attention-related posterior brain regions (especially temporo-occipital areas) are activated in ADHD-RI during both Go and No-Go cues compared to TD controls and ADHD predominantly inattentive type. ADHD-RI may represent a different phenotype than other types of ADHD. In addition, our results suggest that reducing the phenotypic heterogeneity may aid in the search for the neurobiological underpinnings of ADHD.

Background Metabolic, morphological, and functional brain changes associated with a neurological deficit in hyperthyroidism have been observed. However, changes in microstructural white matter (WM), which can explain the underlying pathophysiology of brain dysfunctions, have not been researched. Purpose To assess microstructural WM abnormality in patients with untreated or newly diagnosed hyperthyroidism using tract-based spatial statistics (TBSS). Material and Methods Eighteen patients with hyperthyroidism and 14 age- and sex-matched healthy controls were included in this study. TBSS were used in this diffusion tensor imaging study for a whole-brain voxel-wise analysis of fractional anisotropy, mean diffusivity, axial diffusivity (AD), and radial diffusivity (RD) of WM. Results When compared to the control group, TBSS showed a significant increase in the RD of the corpus callosum, anterior and posterior corona radiata, posterior thalamic radiation, cingulum, superior longitudinal fasciculus, and the retrolenticular region of the internal capsule in patients with hyperthyroidism (P < 0.05), as well as a significant decrease in AD in the anterior corona radiata and the genu of corpus callosum (P < 0.05). Conclusion This study showed that more regions are affected by the RD increase than the AD decrease in the WM tracts of patients with hyperthyroidism. These preliminary results suggest that demyelination is the main mechanism of microstructural alterations in the WM of hyperthyroid patients.