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• A phase-field approach to investigate crack nucleation and propagation in martensitic microstructures. • A coupled system of the time-dependent Ginzburg-Landau equation and the equilibrium equation. • Multi-variant martensitic phase transformations within the framework of a finite element method. • Martensitic specimen, with and without pre-existing crack, according to three types of martensitic embryo(s). In this work, a phase-field approach (PFA) is presented to study crack nucleation and propagation in martensitic micro-structures resulted from multi-variant martensitic phase transformations (MPT) within the framework of a finite element method (FEM). To this end, first, a coupled system of the time-dependent Ginzburg-Landau (TDGL) equation and the equilibrium equation is established based on the micro-elasticity theory, which reveals the nucleation and growth of diffusionless martensitic multi-variants forming a twinned martensitic micro-structure. The Helmholtz free energy used in this work consists of a second-degree polynomial of the phase variable, which leads to a nonlinear dependence on the order parameter in the TGDL equation. Thereafter, the nucleation and propagation of a crack is scrutinized in the obtained martensitic specimen, with and without pre-existing crack, according to three types of martensitic embryos. To do so, a damage variable is introduced to the multi-variant MPT model to study the interactions between the martensitic transformation and fracture. The key contributions of this study are not only to shed light on the evolution of the martensitic variants in the micro-structure with three types of pre-existing martensitic embryos, but also to investigate onset and growth of a crack in the martensitic specimen. [ABSTRACT FROM AUTHOR]

Deep brain stimulation (DBS) targeting the anterior nucleus of the thalamus (ANT) is as an effective and safe treatment option for patients with resistant epilepsy. A SANTE Study reported that there was a gradual improvement in selected neuropsychological test results in patient with DBS in ANT. Among those improvements there were reported a number of psychiatric adverse affects. However little is studied about immediate neuropsychological effects of DBS in ANT. Recently demonstrated Voges B. et. al (2015) a stimulus- and voltage-dependent effect interrupting sleep and leading to the occurrence of neuropsychiatric symptoms (npS) (e.g. depression, mood instability, disturbed sleep) during ATN-DBS. We here present one patient with a voltage-independent developing of npS during ANT-DBS. The 45-year-old right-handed female patient with mental retardation with autistic spectrum disorder presented with focal not lesional refractory epilepsy. The average seizure frequency was 6.1 per day with a range of 1 to 16 seizures daily. After failure of 13 AED"s, a DBS-ANT was initiated at the age of 44. Follow up simultaneous EEG- video recording from 26 surface electrode contacts after beginning to stimulate with standard parameters (unipolar cyclic (1min ON/5min OFF) stimulation with 5 V stimulation amplitude, 120 Hz stimulation frequency and a pulse width of 90 μs) there were seen a directly dependence of neuropsychiatric symptoms (stereotypical movements with sitting down, torso wiggling (Body rocking) with or without singing) and impulse onset. In video-EEG monitoring we determined, that the duration of npS was also the same as impulse lasts. A clinical response to stimulation was 84 %. We improve adverse effects changing the programming settings: the amplitude was gradually reduced to two volts, the stimulation frequency 120 Hz and a pulse width of 90 μs where the same. Actual case report devoted to immediate complex behavioural disorder, which does not fulfil criteria for a complex focal seizure, and is strongly associated with unipolar bilateral stimulation of ANT. The actual clinical presentation of the DBS induced behavioural disorder semiologically coincide with the term "stereotypic movement disorder". We hypothesize that impaired function of ARAS lead to reduced behavioural suppression of impulse mediated behaviour in the patient with mental retardation. We analysed her video-EEG before she was being stimulated and noticed, that she already had a typical body movement (body rocking) but much less frequently. Obviously a DBS of ANT had had a strong influence on behavioural disorder of our patient and was reversible after adjusting the stimulation parameters. [ABSTRACT FROM AUTHOR]

Highlights: [•] Damage of the optical radiation is reported after resective epilepsy surgery. [•] Postchiasmal pathway and visual cortex vary anatomically in between individuals. [•] Therefore, anatomically based tractography might be inferior to a functional approach. [•] Regions of interest for tractography were identified with fMRI-based retinotopy. [•] Functionally based tractography proves feasible during presurgical epilepsy work up. [Copyright &y& Elsevier]

We report electrophysiological findings from Deep brain stimulation (DBS) of the internal globus pallidus (GPi) and ventral intermediate thalamic nucleus (VIM) in a patient with genetically proven Myoclonus–Dystonia–Syndrom (DYT11). The syndromes of the patient were refractory to medical treatment. Methods We performed a quadruple stimulation in VIM and GPi bilaterally and recorded electrophysiological data 3 days postoperatively. We assessed local field potentials and calculated coherence between electrodes ( n = 4 per electrode trajectory, denoted as 0–3, being 0 most ventral and 3 most dorsal contact) and transfer entropy for assessment of the “information” flow in different DBS and resting conditions. Stimulation was performed with 120 Hz. Results Clinically, the patient did not show any MDS symptoms at the time of the recordings (lesion effect). At rest the predominant electrophysiological pattern comprised VIM: 7–11 Hz, GPi: 3–10 Hz bands and showed significantly higher amplitudes for the Theta and alpha bands in right VIM (contacts 0–1, 1–2). No coherence between the LFPs measured and muscle activity measured with surface electrodes on neck and arm muscles was observed, likely due to postoperative lesion effect. We then measured the effects of stimulation of one structure (VIM or GPi) on the other structure (GPi or VIM). Stimulation of the right and the left VIM showed no changes in coherence and transfer entropy in the GPi. However stimulation of the left VIM contacts 0–1/1–2 resulted in a significant increase of the amplitude of the theta-band in the right GPI 0–1/2–3. Stimulation of the left GPi at 0–1/2–3 significantly increased the amplitude in the alpha band of both VIMs. Similarly, coherence levels were also raised by low frequency stimulation at approximately 9–11 Hz. Concomittantly, a diffuse change in the transfer entropy was observed: Stimulating the left GPi 0–1/2–3 increased significantly the amplitude of the alpha frequencies in the right VIM 1–2. Finally we compared the effects of DBS of VIM and GPi of one side to the other. Simultaneous stimulation of the right VIM 0–1, 2–3 and right GPi 0–1, 2–3 significantly lowered the alpha band of the left GPi 0–1. Again, there were no changes in the coherence and the transfer entropy. In contrast stimulation of the left VIM and GPi showed no effect in amplitude, coherence nor transfer entropy in the right GPi and VIM. Conclusion We could show via stimulation of the left VIM a possible connection between the left VIM and the right GPi and vice versa, although there was no change in the transfer entropy. These results point to relais stations or other structural connections between thalamus and pallidum. In summary, thalamic or pallidal stimulation in MDS seem to be encompassing differential, though partially interconnected neurophysiological pathways. The present data provide electrophysiologcal evidence for the notion of potential beneficial quadruple DBS in MDS ( Gruber et al., 2010 ). [ABSTRACT FROM AUTHOR]