Multishell Diffusion MRI-Based Tractography of the Facial Nerve in Vestibular Schwannoma.

BACKGROUND AND PURPOSE: Tractography of the facial nerve based on single-shell diffusion MR imaging is thought to be helpful before surgery for resection of vestibular schwannoma. However, this paradigm can be vitiated by the isotropic diffusion of the CSF, the convoluted path of the facial nerve, and its crossing with other bundles. Here we propose a multishell diffusion MR imaging acquisition scheme combined with probabilistic tractography that has the potential to provide a presurgical facial nerve reconstruction uncontaminated by such effects. MATERIALS AND METHODS: Five patients scheduled for vestibular schwannoma resection underwent multishell diffusion MR imaging (b-values = 0, 300, 1000, 2000 s/mm2). Facial nerve tractography was performed with a probabilistic algorithm and anatomic seeds located in the brain stem, cerebellopontine cistern, and internal auditory canal. A single-shell diffusion MR imaging (b-value = 0, 1000 s/mm2) subset was extrapolated from the multishell diffusion MR imaging data. The quality of the facial nerve reconstruction based on both multishell diffusion MR imaging and single-shell diffusion MR imaging sequences was assessed against intraoperative videos recorded during the operation. RESULTS: Single-shell diffusion MR imaging-based tractography was characterized by failures in facial nerve tracking (2/5 cases) and inaccurate facial nerve reconstructions displaying false-positives and partial volume effects. In contrast, multishell diffusion MR imaging-based tractography provided accurate facial nerve reconstructions (4/5 cases), even in the presence of ostensibly complex patterns. CONCLUSIONS: In comparison with single-shell diffusion MR imaging, the combination of multishell diffusion MR imaging-based tractography and probabilistic algorithms is a more valuable aid for surgeons before vestibular schwannoma resection, providing more accurate facial nerve reconstructions, which may ultimately improve the postsurgical patient's outcome.

Increase of CSF inflammatory profile in a case of highly active multiple sclerosis.

BACKGROUND: Clinical and imaging follow-up coupled with cerebrospinal fluid (CSF) and possibly serum profiling could provide information on disease activity and disability evolution in multiple sclerosis patients. CASE PRESENTATION: We describe the case of a relapsing-remitting MS patient whose history was characterized by failure of several therapeutic approaches and sustained disease activity. By using a highly sensitive immunoassay methodology, we examined protein expression of 70 inflammatory/cytotoxic molecules in two consecutive paired CSF and serum samples, obtained respectively in 2006 and 2013. At disease diagnosis, elevated CSF protein levels of an inflammatory pattern, including CXCL13, CXCL12, IFNγ, TNF, sTNFR1, IL8, sCD163, APRIL, BAFF, pentraxin III and MMP2 were found compared with a group of controls. At the second lumbar puncture, sustained disease activity was accompanied by considerable (more than 2 fold changes) increase expression of most of these inflammatory molecules while no significant changes in serum inflammatory markers were detected in the two consecutive serum samples. CONCLUSIONS: Elevated CSF protein expression of pro-inflammatory mediators, possibly specifically associated to GM demyelination, could remain stable or increase over time in patients with active multiple sclerosis. We underline the role of fluid analysis in understanding the pathophysiology of the disease and providing information on possible markers of disease activity and evolution.

Heterogeneity of Cortical Lesion Susceptibility Mapping in Multiple Sclerosis.

BACKGROUND AND PURPOSE: Quantitative susceptibility mapping has been used to characterize iron and myelin content in the deep gray matter of patients with multiple sclerosis. Our aim was to characterize the susceptibility mapping of cortical lesions in patients with MS and compare it with neuropathologic observations. MATERIALS AND METHODS: The pattern of microglial activation was studied in postmortem brain tissues from 16 patients with secondary-progressive MS and 5 age-matched controls. Thirty-six patients with MS underwent 3T MR imaging, including 3D double inversion recovery and 3D-echo-planar SWI. RESULTS: Neuropathologic analysis revealed the presence of an intense band of microglia activation close to the pial membrane in subpial cortical lesions or to the WM border of leukocortical cortical lesions. The quantitative susceptibility mapping analysis revealed 131 cortical lesions classified as hyperintense; 33, as isointense; and 84, as hypointense. Quantitative susceptibility mapping hyperintensity edge found in the proximity of the pial surface or at the white matter/gray matter interface in some of the quantitative susceptibility mapping-hyperintense cortical lesions accurately mirrors the microglia activation observed in the neuropathology analysis. CONCLUSIONS: Cortical lesion susceptibility maps are highly heterogeneous, even at individual levels. Quantitative susceptibility mapping hyperintensity edge found in proximity to the pial surface might be due to the subpial gradient of microglial activation.

A Variational Bayesian inference method for parametric imaging of PET data.

In dynamic Positron Emission Tomography (PET) studies, compartmental models provide the richest information on the tracer kinetics of the tissue. Inverting such models at the voxel level is however quite challenging due to the low signal-to-noise ratio of the time activity curves. In this study, we propose the use of a Variational Bayesian (VB) approach to efficiently solve this issue and thus obtain robust quantitative parametric maps. VB was adapted to the non-uniform noise distribution of PET data. Moreover, we propose a novel hierarchical scheme to define the model parameter priors directly from the images in case such information are not available from the literature, as often happens with new PET tracers. VB was initially tested on synthetic data generated using compartmental models of increasing complexity, providing accurate (%bias<2%±2%, root mean square error<15%±5%) parameter estimates. When applied to real data on a paradigmatic set of PET tracers (L-[1-11C]leucine, [11C]WAY100635 and [18F]FDG), VB was able to generate reliable parametric maps even in presence of high noise in the data (unreliable estimates<11%±5%).

Epilepsy in multiple sclerosis: The role of temporal lobe damage.

BACKGROUND: Although temporal lobe pathology may explain some of the symptoms of multiple sclerosis (MS), its role in the pathogenesis of seizures has not been clarified yet. OBJECTIVES: To investigate the role of temporal lobe damage in MS patients suffering from epilepsy, by the application of advanced multimodal 3T magnetic resonance imaging (MRI) analysis. METHODS: A total of 23 relapsing remitting MS patients who had epileptic seizures (RRMS/E) and 23 disease duration matched RRMS patients without any history of seizures were enrolled. Each patient underwent advanced 3T MRI protocol specifically conceived to evaluate grey matter (GM) damage. This includes grey matter lesions (GMLs) identification, evaluation of regional cortical thickness and indices derived from the Neurite Orientation Dispersion and Density Imaging model. RESULTS: Regional analysis revealed that in RRMS/E, the regions most affected by GMLs were the hippocampus (14.2%), the lateral temporal lobe (13.5%), the cingulate (10.0%) and the insula (8.4%). Cortical thinning and alteration of diffusion metrics were observed in several regions of temporal lobe, in insular cortex and in cingulate gyrus of RRMS/E compared to RRMS ( p< 0.05 for all comparisons). CONCLUSIONS: Compared to RRMS, RRMS/E showed more severe damage of temporal lobe, which exceeds what would be expected on the basis of the global GM damage observed.

Características diferenciales de la interacción colaborativa entre niños según el nivel socioeconómico, en dos tipos de tarea / No disponible

El objetivo de la presente investigación fue analizar las diferencias que se observan en el proceso de colaboración entre pares según el nivel socioeconómico (NSE), en la realización de dos tipos de tarea, una predominantemente lógica (construcción de una casa con bloques) y otra predominantemente expresiva (dibujo libre). Participaron 56 niños de entre ocho y doce años agrupados en 28 díadas, 16 de NSE favorecido y 12 de NSE desfavorecido. La colaboración fue analizada en función de dos dimensiones: la interacción verbal (tipos de mensaje) y la modalidad social de ejecución de la tarea. Las diferencias principales constatadas entre ambos NSE conciernen, sobre todo, a la interacción verbal registrada en la tarea de construcción. En cambio, se observaron diferencias menores en lo que hace a la interacción verbal en el dibujo libre. Tampoco se encontraron, de modo general, importantes variaciones respecto a la modalidad o patrón social de ejecución en ambas tareas, aunque sí en algunos aspectos puntuales de dicha modalidad (AU)

The aim of this research was to analyze the differences that can be observed among children from different socioeconomic status (SES) in a collaborative process, in which they had to deal with two tasks: a logical task (building a house with blocks) and an expressive task (free drawing). Participants were 56 children between eight and twelve years old which were grouped in 28 pairs. 16 of these pairs came from an advantaged SES, while the other 12 pairs came from a disadvantaged SES. The analysis focused in two dimensions: verbal interaction (type of message) and social pattern of execution. Main differences between both SES concerned to verbal interaction registered in the construction task. However not so many differences regarding verbal interactions were observed in the free drawing task. When analyzing the social pattern of execution in both tasks no significant differences were found in the general process, although some particular aspects showed variations between both group (AU)