No abstract

It is well established that the mid-dorsolateral prefrontal cortex (dlPFC) plays a critical role in planning. Neuroimaging studies have yielded predominantly bilateral dlPFC activations, but the existence and nature of functionally specific contributions of left and right dlPFC have remained elusive. In recent experiments, 2 independent parameters have been identified which substantially determine planning: 1) the degree of interdependence between consecutive steps (search depth) and 2) the degree to which the configuration of the goal state renders the order of single steps either clearly evident or ambiguous (goal hierarchy). Thus, search depth affects the actual mental generation and evaluation of action sequences, whereas goal hierarchy reflects the extraction of goal information from an encountered problem. Here, both parameters were independently manipulated in an event-related functional magnetic resonance imaging study using the Tower of London task. Results revealed a double dissociation as indicated by a significant crossover interaction of hemisphere and task parameter: in left dlPFC, activations were stronger for higher demands on goal hierarchy than on search depth, whereas the reversed result emerged in right dlPFC. In conclusion, often observed bilateral patterns of dlPFC activation in complex tasks may reflect the concomitant operation of specific cognitive processes that show opposing lateralizations.

To determine three-dimensional (3D) blood flow patterns in the carotid bifurcation, 10 healthy volunteers and nine patients with internal carotid artery (ICA) stenosis ≥50% were examined by flow-sensitive 4D MRI at 3T. Absolute and mean blood velocities, pulsatility index (PI), and resistance index (RI) were measured in the common carotid arteries (CCAs) by duplex sonography (DS) and compared with flow-sensitive 4D MRI. Furthermore, 3D MRI blood flow patterns in the carotid bifurcation of volunteers and patients before and after recanalization were graded by two independent readers. Blood flow velocities measured by MRI were 31-39% lower than in DS. However, PI and RI differed by only 13-16%. Rating of 3D flow characteristics in the ICA revealed consistent patterns for filling and helical flow in volunteers. In patients with ICA stenosis, 3D blood flow visualization was successfully employed to detect markedly al- The assessment of the severity and progression of internal carotid artery (ICA) stenosis is of clinical interest since high-grade stenoses constitute a major source of ischemic stroke. While the influence of cardiovascular risk factors on the common carotid artery (CCA) is expressed by a proportional increase of intima-media thickness and decrease of vessel distensibility (1,2), the development of atherosclerosis in the naturally bulbar ICA is related to anatomical and local hemodynamic conditions such as flow deceleration and reduced and oscillating wall shear stress (WSS), as shown in vitro, in animal models, and in two-dimensional (2D) MRI studies of healthy volunteers (3-9).However, current clinical diagnostic tools are limited since they provide either functional (2D duplex sonography [DS]) or morphological (digital subtraction, CT, or MR angiography [MRA]) data (10 -12). At present, a combined assessment and analysis of both anatomy and function in 3D is not available. While the evaluation of carotid plaque composition by MRI is well established (12), associated individual 3D blood flow patterns that influence plaque type, as recently shown by Cheng et al. (7), have not yet been studied in humans by MRI in vivo. Furthermore, little is known about the underlying flow characteristics, such as helical flow in the bulb of ICA and its relationship to the development of carotid artery stenosis.In this context, time-resolved phase-contrast (PC) MRI with three-directional velocity encoding (flow-sensitive 4D MRI) provides full hemodynamic information on 3D blood flow for both left and right carotid bifurcations. Previously reported results demonstrated the potential of this technique for the assessment of normal and altered blood flow in the heart and the aorta (13-19). In a number of studies, advanced 3D visualization of blood flow based on vector fields, 3D streamlines, and time-resolved 3D particle traces was successfully employed to detect and illustrate complex in vivo 3D blood flow patterns (20 -26).Moreover, application of this MRI technique to intracranial and peripheral vessels yielded objective...

Background: Endovascular treatment has become standard of care for the treatment of acute ischemic stroke with large vessel occlusion. However, patients treated in clinical practice differ from the selected populations randomized in clinical trials. Aims: The German Stroke Registry Endovascular Treatment (GSR-ET) aims at a systematic evaluation of outcome, safety, and process parameters of endovascular stroke treatment in standard of care in Germany. Methods: The GSR-ET is an academic, independent, prospective, multicenter, observational registry study. Participating stroke centers from all over of Germany consecutively enroll patients transferred to the angiography suite with an intention to be treated with endovascular stroke treatment. Patients receive regular care. Data are collected as part of clinical routine. Baseline clinical and procedural information and clinical follow-up information after 90 days are recorded. Here, we present an analysis of baseline data of the first 1662 patients included in the GSR-ET. Results: The registry was established in June 2015. By 31 December 2017, 1662 patients were enrolled in 23 active sites. Mean age was 72 AE 13 years, 50% were female, and median National Institutes of Health Stroke Scale on admission was 15 (IQR 10-19), 88% had anterior circulation occlusion. Median ASPECT score was 8 (IQR 7-10) prior to intervention. Fifty-nine percent of patients received intravenous thrombolysis prior to thrombectomy. Mean ''onset-to-groin'' time was 224 AE 176 min. Conclusions: Baseline characteristics of stroke patients undergoing thrombectomy in clinical practice differ from those in the randomized trials. The GSR-ET will provide valuable insights into practices of endovascular treatment in routine care of acute ischemic stroke. (GSR-ET ClinicalTrials.gov Identifier: NCT03356392.

Summary:Purpose: Focal cortical dysplasia (FCD) is a frequent cause of partial epilepsy. Its diagnosis by visual evaluation of magnetic resonance images (MRIs) remains difficult. The purpose of this study was to apply a novel automated and observer-independent voxel-based technique for the analysis of 3-dimensional (3-D) MRI to detect and localize FCD.Methods: The technique was based on algorithms of the SPM99 software and included the spatial normalization of 3-D MRI data sets to a common stereotaxic space and the segmentation of cortical grey matter. The resulting data sets represented grey-matter density maps where each voxel encoded the grey-matter concentration at the corresponding position in the original MRI. A normal database was set up by calculating and averaging the grey-matter density maps of 30 healthy volunteers. The MRI data sets of seven epilepsy patients with FCD were evaluated retrospectively for dysplastic lesions by voxelwise subtraction of the mean grey-matter density map of the normal database and searching automatically for local and global maxima in the resulting data set.Results: In all patients, the results of voxel-based 3-D MRI analysis corresponded both to the location of the dysplastic lesions in conventional MRI and to seizure semiology and EEG findings. In one case, surgery was performed, and the diagnosis FCD was supported by histology.Conclusions: The technique of voxel-based 3-D MRI analysis and comparison with a normal database seems to provide a valuable additional screening tool for the detection of FCD.