Quantitative Susceptibility Mapping Indicates a Disturbed Brain Iron Homeostasis in Neuromyelitis Optica - A Pilot Study.

Dysregulation of brain iron homeostasis is a hallmark of many neurodegenerative diseases and can be associated with oxidative stress. The objective of this study was to investigate brain iron in patients with Neuromyelitis Optica (NMO) using quantitative susceptibility mapping (QSM), a quantitative iron-sensitive MRI technique. 12 clinically confirmed NMO patients (6 female and 6 male; age 35.4y±14.2y) and 12 age- and sex-matched healthy controls (7 female and 5 male; age 33.9±11.3y) underwent MRI of the brain at 3 Tesla. Quantitative maps of the effective transverse relaxation rate (R2*) and magnetic susceptibility were calculated and a blinded ROI-based group comparison analysis was performed. Normality of the data and differences between patients and controls were tested by Kolmogorov-Smirnov and t-test, respectively. Correlation with age was studied using Spearman's rank correlation and an ANCOVA-like analysis. Magnetic susceptibility values were decreased in the red nucleus (p<0.01; d>0.95; between -15 and -22 ppb depending on reference region) with a trend toward increasing differences with age. R2* revealed significantly decreased relaxation in the optic radiations of five of the 12 patients (p<0.0001; -3.136±0.567 s(-1)). Decreased relaxation in the optic radiation is indicative for demyelination, which is in line with previous findings. Decreased magnetic susceptibility in the red nucleus is indicative for a lower brain iron concentration, a chemical redistribution of iron into less magnetic forms, or both. Further investigations are necessary to elucidate the pathological cause or consequence of this finding.

In vivo assessment of white matter damage in neuromyelitis optica: a diffusion tensor and diffusion kurtosis MR imaging study.

BACKGROUND AND PURPOSE: In patients with neuromyelitis optica (NMO), damage to extensive regions of normal-appearing WM has been observed. To investigate the possibility that microstructural alterations are present in these WM tracts, DTI and diffusion kurtosis imaging (DKI) techniques were applied and compared. MATERIAL AND METHODS: Thirteen patients with NMO and 13 demographically and gender-matched controls underwent MRI using a 3T MR scanner, with DTI/DKI sequence acquired jointly fitted. Parametric fractional anisotropy maps were derived from diffusion tensor (FADTI) values using b-values of 0s/mm(2) and 1000s/mm(2). Parametric fractional anisotropy maps derived from diffusion kurtosis tensor (FADKI) values were also acquired using b-values of 0, 1000, and 2000s/mm(2). Mean FADTI and FADKI values were also calculated. A ROI analysis of the genu and splenium of the corpus callosum (CC), cerebral peduncle (CP), and optic radiation (OR) was also performed. Student's t-test and corrections for multiple comparisons were used to evaluate the data obtained. RESULTS: A significant decrease in the FADTI values obtained for NMO patients versus controls was observed for the splenium of the CC and the left OR (p<0.05). However, just a positive trend was observed for the FADKI values associated with the same WM tracts. CONCLUSIONS: To our knowledge, this is the first study to analyze WM tracts of NMO patients using DTI and DKI. These data indicate that DKI could have limitations in evaluating the WM integrity in NMO patients. Furthermore, the results obtained are consistent with the hypothesis that diffuse brain involvement characterizes NMO.

Cuneus and fusiform cortices thickness is reduced in trigeminal neuralgia.

BACKGROUND: Chronic pain disorders are presumed to induce changes in brain grey and white matters. Few studies have focused CNS alterations in trigeminal neuralgia (TN). METHODS: The aim of this study was to explore changes in white matter microstructure in TN subjects using diffusion tensor images (DTI) with tract-based spatial statistics (TBSS); and cortical thickness changes with surface based morphometry. Twenty-four patients with classical TN (37-67 y-o) and 24 healthy controls, matched for age and sex, were included in the study. RESULTS: Comparing patients with controls, no diffusivity abnormalities of brain white matter were detected. However, a significant reduction in cortical thickness was observed at the left cuneus and left fusiform cortex in the patients group. The thickness of the fusiform cortex correlated negatively with the carbamazepine dose (p = 0.023). CONCLUSIONS: Since the cuneus and the fusiform gyrus have been related to the multisensory integration area and cognitive processing, as well as the retrieval of shock perception conveyed by Aδ fibers, our results support the role of these areas in TN pathogenesis. Whether such changes occurs as an epiphenomenon secondary to daily stimulation or represent a structural predisposition to TN in the light of peripheral vascular compression is a matter of future studies.

Advanced magnetic resonance imaging techniques in the evaluation of pediatric white matter diseases.

This article aimed to describe the technical principles and clinical application of advanced magnetic resonance imaging techniques for the assessment of white matter diseases. The following techniques are going to be discussed: magnetization transfer, proton magnetic resonance spectroscopy, diffusion-weighted imaging, diffusion tensor imaging, as well as perfusion and postprocessing techniques such as tract-based spatial statistics. These techniques allow a better understanding of the physiopathology of the white matter diseases as well as have a significant impact on the definition of the differential diagnosis and treatment options.

In vivo evaluation of cortical thickness with magnetic resonance imaging in patients with bipolar disorder

Changes in cortical thickness can be related to neuropsychiatric disorders and neurodegenerative processes. Previous studies have been conducted to characterize the pattern of changes in cortical thickness in several psychiatric diseases. The aim of the present study was to evaluate changes in cortical thickness with magnetic resonance imaging (MRI) in patients with bipolar disorder. Twenty-seven patients with bipolar disorder (14 male, 36.0 ± 16.2 years old; 13 female, 41.6 ± 10.7 years old) and 40 healthy controls (16 male, 36.0 ± 10.5 years old; 24 female, 37.0 ± 4.7 years old) underwent 3T MRI. Sagittal T1-weighted magnetization prepared rapid acquisition gradient echo images were acquired (voxel size, 1.33 mm³; 128 slices; in-plane matrix resolution, 256 × 256; flip angle, 7º; repetition time, 2530 ms; echo time, 3.39 ms; inversion time, 1100 ms). Cortical segmentation was performed using FreeSurfer 4.0.5. The results indicated both thinning and thickening of the cerebral cortex in patients with bipolar disorder compared with controls, depending on gender. Significant (p < .01) thickening was observed in the right hemisphere superior-parietal cortex in female patients with bipolar disorder, and significant (p < .05) thinning was observed in the left hemisphere caudal-anterior cingulate in male patients with bipolar disorder. The other regions did not show significant differences. The results suggest that an analysis of cortical thickness with MRI in patients with bipolar disorder may allow identification of areas that may be morphologically changed compared with controls. Demonstration of these alterations will elucidate the pathophysiology of bipolar disorder and may contribute to better therapies for this disorder.