Homoepitaxy of Boron Nitride on Exfoliated Hexagonal Boron Nitride Flakes.

Although large efforts have been made to improve the growth of hexagonal boron nitride (hBN) by heteroepitaxy, the non-native substrates remain a fundamental factor that limits the quality. This problem can be solved by homoepitaxy, which is the growth of hBN on hBN substrates. In this report, we demonstrate the homoepitaxial growth of triangular BN grains on exfoliated hBN flakes by Metal-Organic Vapor Phase Epitaxy and show by atomic force microscopy and photoluminescence that the stacking of these triangular islands can deviate from the AA' stacking of hBN. We show that the stacking order is enforced by the crystallographic direction of the edge of the exfoliated hBN flakes, with armchair edges allowing for centrosymmetric stacking, whereas zigzag edges lead to the growth of noncentrosymmetric BN polytypes. Our results indicate pathways to grow homoepitaxial BN with tunable layer stacking, which is required to induce piezoelectricity or ferroelectricity.

Strain modulation of epitaxial h-BN on sapphire: the role of wrinkle formation for large-area two-dimensional materials.

Strain built-in electronic and optoelectronic devices can influence their properties and lifetime. This effect is particularly significant at the interface between two-dimensional materials and substrates. One such material is epitaxial hexagonal boron nitride (h-BN), which is grown at temperatures often exceeding 1000 °C. Due to the high growth temperature, h-BN based devices operating at room temperature can be strongly affected by strain generated during cooling due to the differences in lattice thermal expansion of h-BN and the substrate. Here, we present results of temperature-dependent Raman studies of the in-plane E2ghighphonon mode in the temperature range of 300-1100 K measured for h-BN grown by metalorganic vapor phase epitaxy. We observe a change, by an order of magnitude, in the rate of the temperature-induced frequency shift for temperatures below 900 K, indicating a strong reduction of the effective h-BN/substrate interaction. We attribute this behavior to the creation of h-BN wrinkles which results in strain relaxation. This interpretation is supported by the observation that no change of layer/substrate interaction and no wrinkles are observed for delaminated h-BN films transferred onto silicon. Our findings demonstrate that wrinkle formation is an inherent process for two-dimensional materials on foreign substrates that has to be understood to allow for the successful engineering of devices based on epitaxially grown van der Waals heterostructures.

All-BN distributed Bragg reflectors fabricated in a single MOCVD process.

Distributed Bragg Reflectors (DBR) are well-established photonic structures that are used in many photonic applications. However, most of the DBRs are based on different materials or require post-process etching which can hinder integration with other components in the final photonic structure. Here, we demonstrate the fabrication of DBR structures consisting only of undoped boron nitride (BN) layers with high refractive index contrast by using metal-organic chemical vapor deposition (MOCVD). This has been achieved in a single process, without the need for any post-process etching. The difference in the refractive index of the component BN layers stems from different degrees of porosity of the individual BN layers, which is a direct result of a different growth temperature. The fabricated DBR structures consist of 15.5 pairs of BN layers and exhibit a reflectance of 87 ± 1% at the maximum. The wavelength of maximum reflectance can be tuned from 500 nm up to the infrared region (IR), by simply adjusting the growth periods of subsequent BN layers. We also demonstrate that the fabricated structures can be used to create an optical microcavity. The fabricated DBRs are very promising candidates for future applications, for example in combination with single-photon emitters in h-BN, which could allow the building of a cavity-based all-BN single-photon source.

Epitaxial Hexagonal Boron Nitride for Hydrogen Generation by Radiolysis of Interfacial Water.

Hydrogen is an important building block in global strategies toward a future green energy system. To make this transition possible, intense scientific efforts are needed, also in the field of materials science. Two-dimensional crystals, such as hexagonal boron nitride (hBN), are very promising in this regard, as it has been demonstrated that micrometer-sized flakes are excellent barriers to molecular hydrogen. However, it remains an open question whether large-area layers fabricated by industrially relevant methods preserve such promising properties. In this work, we show that electron-beam-induced splitting of water creates hBN bubbles that effectively store molecular hydrogen for weeks and under extreme mechanical deformation. We demonstrate that epitaxial hBN allows direct visualization and monitoring of the process of hydrogen generation by radiolysis of interfacial water. Our findings show that hBN is not only a potential candidate for hydrogen storage but also holds promise for the development of unconventional hydrogen production schemes.

Adult-Onset Neurodegeneration in Nucleotide Excision Repair Disorders (NERDND ): Time to Move Beyond the Skin.

BACKGROUND: Variants in genes of the nucleotide excision repair (NER) pathway have been associated with heterogeneous clinical presentations ranging from xeroderma pigmentosum to Cockayne syndrome and trichothiodystrophy. NER deficiencies manifest with photosensitivity and skin cancer, but also developmental delay and early-onset neurological degeneration. Adult-onset neurological features have been reported in only a few xeroderma pigmentosum cases, all showing at least mild skin manifestations. OBJECTIVE: The aim of this multicenter study was to investigate the frequency and clinical features of patients with biallelic variants in NER genes who are predominantly presenting with neurological signs. METHODS: In-house exome and genome datasets of 14,303 patients, including 3543 neurological cases, were screened for deleterious variants in NER-related genes. Clinical workup included in-depth neurological and dermatological assessments. RESULTS: We identified 13 patients with variants in ERCC4 (n = 8), ERCC2 (n = 4), or XPA (n = 1), mostly proven biallelic, including five different recurrent and six novel variants. All individuals had adult-onset progressive neurological deterioration with ataxia, dementia, and frequently chorea, neuropathy, and spasticity. Brain magnetic resonance imaging showed profound global brain atrophy in all patients. Dermatological examination did not show any skin cancer or pronounced ultraviolet damage. CONCLUSIONS: We introduce NERDND as adult-onset neurodegeneration (ND ) within the spectrum of autosomal recessive NER disorders (NERD). Our study demonstrates that NERDND is probably an underdiagnosed cause of neurodegeneration in adulthood and should be considered in patients with overlapping cognitive and movement abnormalities. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Raman Optical Activity of 1T-TaS2.

Measurements of optical activity can be readily performed in transparent matter by means of a rotation of transmitted light polarization. In the case of opaque bulk materials, such measurements cannot be performed, making it difficult to assess possible chiral properties. In this work, we present full angular polarization dependencies of the Raman modes of bulk 1T-TaS2, which has recently been suggested to have chiral properties after pulsed laser excitation. We found that a mechanical rotation of the sample does not alter polarization-resolved Raman spectra, which can only be explained by introducing an antisymmetric Raman tensor, frequently used to describe Raman optical activity (ROA). Raman spectra obtained under circularly polarized excitation demonstrate that 1T-TaS2 indeed shows ROA, providing strong evidence that 1T-TaS2 is chiral under the used conditions of laser excitation. Our results suggest that ROA may be used as a universal tool to study chiral properties of quantum materials.

The third dimension in perforator mapping-Comparison of Cinematic Rendering and maximum intensity projection in abdominal-based autologous breast reconstruction.

BACKGROUND: Cinematic Rendering (CR) is a recently introduced post-processing three-dimensional (3D) visualization imaging tool. The aim of this study was to assess its clinical value in the preoperative planning of deep inferior epigastric artery perforator (DIEP) or muscle-sparing transverse rectus abdominis myocutaneous (MS-TRAM) flaps, and to compare it with maximum intensity projection (MIP) images. The study presents the first application of CR for perforator mapping prior to autologous breast reconstruction. METHODS: Two senior surgeons independently analyzed CR and MIP images based on computed tomography angiography (CTA) datasets of 20 patients in terms of vascular pedicle characteristics, the possibility to harvest a DIEP or MS-TRAM flap, and the side of the flap harvest. We calculated inter- and intra-observer agreement in order to examine the accordance of both image techniques. RESULTS: We observed a good inter- and intra-observer agreement concerning the type of flap and the side of the flap harvest. However, the agreement on the pedicle characteristics varies depending on the considered variable. Both investigators identified a significantly higher number of perforators with MIP compared with CR (observer 1, p<0.0001 and observer 2, p<0.0385). CONCLUSION: The current study serves as an explorative study, showing first experiences with CR in abdominal-based autologous breast reconstruction. In addition to MIP images, CR might improve the surgeon's understanding of the individual's anatomy. Future studies are required to compare CR with other 3D visualization tools and its possible effects on operative parameters.

Collateral effects of the SARS-CoV-2 pandemic on oncologic surgery in Bavaria.

BACKGROUND: The ongoing SARS-COV-2 pandemic has severe implications for people and healthcare systems everywhere. In Germany, worry about the consequences of the pandemic led to the deferral of non-emergency surgeries. Tumor surgery accounts for a large volume in the field of visceral surgery and cannot be considered purely elective. It is not known how the SARS-COV-2 pandemic has changed the surgical volume in tumor patients. METHODS: Retrospective analysis of the amount of oncological surgeries in three academic visceral surgery departments in Bavaria, Germany, in 2020. Procedures were split into subgroups: Upper Gastrointestinal (Upper GI), Colorectal, Hepato-Pancreato-Biliary (HPB), Peritoneal and Endocrine. Procedures in 2020 were compared to a reference period from January 1st, 2017 to December 31st 2019. Surgical volume was graphically merged with SARS-COV-2 incidence and the number of occupied ICU beds. RESULTS: Surgical volume decreased by 7.6% from an average of 924 oncologic surgeries from 2017 to 2019 to 854 in 2020. The decline was temporally associated with the incidence of infections and ICU capacity. Surgical volume did not uniformly increase to pre-pandemic levels in the months following the first pandemic wave with lower SARS-COV-2 incidence and varied according to local incidence levels. The decline was most pronounced in colorectal surgery where procedures declined on average by 26% following the beginning of the pandemic situation. CONCLUSION: The comparison with pre-pandemic years showed a decline in oncologic surgeries in 2020, which could have an impact on lost life years in non-COVID-19 patients. This decline was very different in subgroups which could not be solely explained by the pandemic.

Heteroepitaxial Growth of High Optical Quality, Wafer-Scale van der Waals Heterostrucutres.

Transition metal dichalcogenides (TMDs) are materials that can exhibit intriguing optical properties like a change of the bandgap from indirect to direct when being thinned down to a monolayer. Well-resolved narrow excitonic resonances can be observed for such monolayers although only for materials of sufficient crystalline quality and so far mostly available in the form of micrometer-sized flakes. A further significant improvement of optical and electrical properties can be achieved by transferring the TMD on hexagonal boron nitride (hBN). To exploit the full potential of TMDs in future applications, epitaxial techniques have to be developed that not only allow the growth of large-scale, high-quality TMD monolayers but also allow the growth to be performed directly on large-scale epitaxial hBN. In this work, we address this problem and demonstrate that MoSe2 of high optical quality can be directly grown on epitaxial hBN on an entire 2 in. wafer. We developed a combined growth theme for which hBN is first synthesized at high temperature by metal organic vapor phase epitaxy (MOVPE) and as a second step MoSe2 is deposited on top by molecular beam epitaxy (MBE) at much lower temperatures. We show that this structure exhibits excellent optical properties, manifested by narrow excitonic lines in the photoluminescence spectra. Moreover, the material is homogeneous on the area of the whole 2 in. wafer with only ±0.14 meV deviation of excitonic energy. Our mixed growth technique may guide the way for future large-scale production of high quality TMD/hBN heterostructures.

[Economic impact of the COVID-19 pandemic in general and visceral surgery : A comparison of performance and revenue data from two departments of hospitals with different levels of referral]. / Ökonomische Auswirkung der COVID-19-Pandemie in der Allgemein- und Viszeralchirurgie : Ein Vergleich von Leistungs- und Erlösdaten zweier Kliniken aus Krankenhäusern unterschiedlicher Versorgungsstufen.

BACKGROUND: During the first wave of the coronavirus disease 2019 (COVID-19) pandemic, German hospitals were required to limit the capacity for elective surgery to prevent the healthcare system from general overload. In March 2020, the German government passed the COVID-19 Hospital Relief Act that guaranteed compensation payments for these limitations. In this study the regional impact of this intervention were analyzed. MATERIAL AND METHODS: The performance data and revenue figures for the departments of general and visceral surgery of the University Hospital of Erlangen (UKER) and the District Hospital St. Anna Höchstadt/Aisch (KKH) during the period from 1 April to 30 June 2019 were compared with the respective period in 2020. RESULTS: There was a significant decrease in bed occupancy rates and case numbers of inpatient treatment. The latter declined by 20.06% in the UKER and 60.76% in the KKH. Nononcological elective surgery was reduced by 33.04% in the UKER and 60.87% in the KKH. The number of emergency procedures remained unchanged in the UKER, while they decreased by 51.58% in the KKH. The revenues from diagnosis-related groups (DRG) decreased by 22.12% (UKER) and 54% (KKH), respectively. After taking compensation payments and savings from variable material costs into account, the UKER recorded a loss of -3.87%, while there was a positive revenue effect of 6.5% in the KKH. DISCUSSION: The nonselective restriction of elective surgery had a significant impact on patient care and revenue figures at both locations. With respect to the increase of intensive care capacities, such untargeted measures do not appear to be efficient. In addition, the fixed rate of compensation payments led to an unbalanced distribution of the financial aid between the two departments.

Cinematic Rendering in Anatomy: A Crossover Study Comparing a Novel 3D Reconstruction Technique to Conventional Computed Tomography.

Integration of medical imaging into preclinical anatomy courses is already underway in many medical schools. However, interpretation of two-dimensional grayscale images is difficult and conventional volume rendering techniques provide only images of limited quality. In this regard, a more photorealistic visualization provided by Cinematic Rendering (CR) may be more suitable for anatomical education. A randomized, two-period crossover study was conducted from July to December 2018, at the University Hospital of Erlangen, Germany to compare CR and conventional computed tomography (CT) imaging for speed and comprehension of anatomy. Sixteen students were randomized into two assessment sequences. During each assessment period, participants had to answer 15 anatomy-related questions that were divided into three categories: parenchymal, musculoskeletal, and vascular anatomy. After a washout period of 14 days, assessments were crossed over to the respective second reconstruction technique. The mean interperiod differences for the time to answer differed significantly between the CR-CT sequence (-204.21 ± 156.0 seconds) and the CT-CR sequence (243.33 ± 113.83 seconds; P < 0.001). Overall time reduction by CR was 65.56%. Cinematic Rendering visualization of musculoskeletal and vascular anatomy was higher rated compared to CT visualization (P < 0.001 and P = 0.003), whereas CT visualization of parenchymal anatomy received a higher scoring than CR visualization (P < 0.001). No carryover effects were observed. A questionnaire revealed that students consider CR to be beneficial for medical education. These results suggest that CR has a potential to enhance knowledge acquisition and transfer from medical imaging data in medical education.

Vorinostat in the acute neuroinflammatory form of X-linked adrenoleukodystrophy.

OBJECTIVE: To identify a pharmacological compound targeting macrophages, the most affected immune cells in inflammatory X-linked adrenoleukodystrophy (cerebral X-ALD) caused by ABCD1 mutations and involved in the success of hematopoietic stem cell transplantation and gene therapy. METHODS: A comparative database analysis elucidated the epigenetic repressing mechanism of the related ABCD2 gene in macrophages and identified the histone deacetylase (HDAC) inhibitor Vorinostat as a compound to induce ABCD2 in these cells to compensate for ABCD1 deficiency. In these cells, we investigated ABCD2 and pro-inflammatory gene expression, restoration of defective peroxisomal ß-oxidation activity, accumulation of very long-chain fatty acids (VLCFAs) and their differentiation status. We investigated ABCD2 and pro-inflammatory gene expression, restoration of defective peroxisomal ß-oxidation activity, accumulation of very long-chain fatty acids (VLCFA) and differentiation status. Three advanced cerebral X-ALD patients received Vorinostat and CSF and MRI diagnostics was carried out in one patient after 80 days of treatment. RESULTS: Vorinostat improved the metabolic defects in X-ALD macrophages by stimulating ABCD2 expression, peroxisomal ß-oxidation, and ameliorating VLCFA accumulation. Vorinostat interfered with pro-inflammatory skewing of X-ALD macrophages by correcting IL12B expression and further reducing monocyte differentiation. Vorinostat normalized the albumin and immunoglobulin CSF-serum ratios, but not gadolinium enhancement upon 80 days of treatment. INTERPRETATION: The beneficial effects of HDAC inhibitors on macrophages in X-ALD and the improvement of the blood-CSF/blood-brain barrier are encouraging for future investigations. In contrast with Vorinostat, less toxic macrophage-specific HDAC inhibitors might improve also the clinical state of X-ALD patients with advanced inflammatory demyelination.

Comparison of Cinematic Rendering and Computed Tomography for Speed and Comprehension of Surgical Anatomy.

Importance: Three-dimensional (3-D) volume rendering has been shown to improve visualization in general surgery. Cinematic rendering (CR), a novel 3-D visualization technology for postprocessing of computed tomographaphy (CT) images, provides photorealistic images with the potential to improve visualization of anatomic details. Objective: To determine the value of CR for the comprehension of the surgical anatomy. Design, Setting, and Participants: This preclinical, randomized, 2-sequence crossover study was conducted from February to November 1, 2018, at University Hospital of Erlangen, Germany. The 40 patient cases were evaluated by 18 resident and attending surgeons using a prepared set of CT and CR images. The patient cases were randomized to 2 assessment sequences (CR-CT and CT-CR). During each assessment period, participants answered 1 question per case that addressed crucial issues of anatomic understanding, preoperative planning, and intraoperative strategies. After a washout period of 2 weeks, case evaluations were crossed over to the respective second image modality. Main Outcomes and Measures: The primary outcome measure was the correctness of answers. Secondary outcome was the time needed to answer. Results: The mean (SD) interperiod differences for the percentage of correct answers in the CR-CT sequence (8.5% [7.0%]) differed significantly from those in the CT-CR sequence (-13.1% [6.3%]) (P < .001). The mean (SD) interperiod differences for the time spent to answer the questions in the CR-CT sequence (-18.3 [76.9] seconds) also differed significantly from those in the CT-CR sequence (52.4 [88.5] seconds) (P < .001). Subgroup analysis revealed that residents as well as attending physicians benefitted from CR visualization. Analysis of the case assessment questionnaire showed that CR added significant value to the comprehension of the surgical anatomy (overall mean [SD] score, 4.53 [0.75]). No carryover or period effects were observed. Conclusions and Relevance: The visualization with CR allowed a more correct and faster comprehension of the surgical anatomy compared with conventional CT imaging, independent of level of surgeon experience. Therefore, CR may assist general surgeons with preoperative preparation and intraoperative guidance.

Leveraging medical imaging for medical education - A cinematic rendering-featured lecture.

BACKGROUND: The integration of medical imaging into anatomical education offers advantages in understanding and learning. However, spatial orientation with conventional (2D) imaging data is challenging, and the students' ability to imagine structures in three dimensions is individual. In addition, the quality of current volume rendering methods is limited. OBJECTIVE: We tested Cinematic Rendering (CR), a novel visualization technique that provides photorealistic volume rendering, in the setting of an interactive anatomy lecture with first-year undergraduate medical and dental students. Our goal was to estimate the acceptance and positive effects CR adds to the subjects. METHODS: A total of 120 students were surveyed with specifically designed self-assessment questionnaires on the use of CR as a tool in anatomical education. RESULTS: Of 120 participating students (87 medical and 33 dental) a large majority of 95.9% (Q3) experienced CR as helpful to understand anatomy better. Overall a large majority of the students experienced CR as helpful for learning and understanding, 85% saw an improvement in anatomical education through the integration of CR (Q3-6) and could also imagine using CR as a self-study tool on an electronic device. CONCLUSION: Our undergraduate medical and dental students experienced CR as a beneficial tool for anatomical education in the chosen setting (lecture) and see further opportunities for the sensible use of this technique. Future research on the topic should include other application possibilities as well.

The optical response of monolayer, few-layer and bulk tungsten disulfide.

We present a comprehensive optical study of thin flakes of tungsten disulfide (WS2) with thickness ranging from mono- to octalayer and in the bulk limit. It is shown that the optical band-gap absorption of monolayer WS2 is governed by competing resonances arising from one neutral and two distinct negatively charged excitons whose contributions to the overall absorption of light vary as a function of temperature and carrier concentration. The photoluminescence response of monolayer WS2 is found to be largely dominated by disorder/impurity- and/or phonon-assisted recombination processes. The indirect band-gap luminescence in multilayer WS2 turns out to be a phonon-mediated process whose energy evolution with the number of layers surprisingly follows a simple model of a two-dimensional confinement. The energy position of the direct band-gap response (A and B resonances) is only weakly dependent on the layer thickness, which underlines an approximate compensation of the effect of the reduction of the exciton binding energy by the shrinkage of the apparent band gap. The A-exciton absorption-type spectra in multilayer WS2 display a non-trivial fine structure which results from the specific hybridization of the electronic states in the vicinity of the K-point of the Brillouin zone. The effects of temperature on the absorption-like and photoluminescence spectra of various WS2 layers are also quantified.

Sub-bandgap Voltage Electroluminescence and Magneto-oscillations in a WSe2 Light-Emitting van der Waals Heterostructure.

We report on experimental investigations of an electrically driven WSe2 based light-emitting van der Waals heterostructure. We observe a threshold voltage for electroluminescence significantly lower than the corresponding single particle band gap of monolayer WSe2. This observation can be interpreted by considering the Coulomb interaction and a tunneling process involving excitons, well beyond the picture of independent charge carriers. An applied magnetic field reveals pronounced magneto-oscillations in the electroluminescence of the free exciton emission intensity with a 1/B periodicity. This effect is ascribed to a modulation of the tunneling probability resulting from the Landau quantization in the graphene electrodes. A sharp feature in the differential conductance indicates that the Fermi level is pinned and allows for an estimation of the acceptor binding energy.

Interprofessional education in Erlangen: A needs analysis and the conceptual work of a student working group.

INTRODUCTION: Interprofessional education (IPE) is receiving growing significance both nationally and internationally. Despite this, organizational and curricular changes are posing challenges. The level of need for IPE and how changes can be made to curricula and infrastructure were investigated at the University of Erlangen in Germany. METHOD: The student working group for interprofessional teaching (AGIL) has turned its attention to these issues. This group is composed of students from medicine, dentistry, molecular medicine, medical technology and speech therapy. In June, 2015, a needs analysis was carried out among the students in the study programs represented in the working group to assess the actual and target situation concerning IPE (n=1,105). In the search for answers and to better measure any needs, contact was sought with instructors. RESULTS: The majority of students feel that they are insufficiently educated in terms of interprofessional skills. A large proportion of the students wish to see expansion of the IPE offerings. Students also expressed a desire for additional spaces and welcomed the idea of an interprofessional learning center. AGIL began establishing interprofessional electives in October 2015. A concept for an interprofessional learning center was developed. DISCUSSION: Based on the survey results, a need for improvements to curricula and infrastructure can be seen; however, the results are limited to the student point of view. AGIL would like to establish more interprofessional electives. These courses would then facilitate curricular implementation. Modern ideas about study environments could be applied to IPE, in particular to promote informal forms of learning. Contact with instructors was crucial for the project work and should be expanded. Realizing and financing the learning center in Erlangen are now the future goals of AGIL. The aim is to create a foundation for this purpose.

Modification of Emission Properties of ZnO Layers due to Plasmonic Near-Field Coupling to Ag Nanoislands.

A simple fabrication method of silver (Ag) nanoislands on ZnO films is presented. Continuous wave and time-resolved photoluminescence and transmission are employed to investigate modifications of visible and UV emissions of ZnO brought about by coupling to localized surface plasmons residing on Ag nanoislands. The size of the nanoislands, determining their absorption and scattering efficiencies, is found to be an important factor governing plasmonic modification of optical response of ZnO films. The presence of the Ag nanoislands of appropriate dimensions causes a strong (threefold) increase in emission intensity and up to 1.5 times faster recombination. The experimental results are successfully described by model calculations within the Mie theory.

Clinical and MRI patterns of pericallosal artery infarctions: the significance of supplementary motor area lesions.

Cerebral infarctions in the anterior cerebral artery (ACA) territory account for only up to 3-5% of strokes. Subject to the affected ACA branches, different clinical patterns can be defined. We report a case series of patients with isolated infarctions of the pericallosal (PC) artery territory. We analyzed 36 consecutive patients presenting over a 10-year period with isolated PC artery territory infarctions (15 left-sided, 19 right-sided, 2 bilateral) regarding clinical symptoms as well as MRI findings. Analysis of DWI lesion pattern showed complete PC artery infarctions in three patients. The majority of patients had partial infarctions predominantly involving either the superior frontal gyrus (n = 12), the corpus callosum (n = 1) or both (n = 20). Hemodynamic lesion patterns were found in 13 patients, while multiple cortical emboli occurred in six. Distal pathology of the ACA (n = 13) was the most frequent MRA finding. Core symptom was contralateral hemiparesis with lower limb predominance (n = 29), partly associated with early-onset spasticity. Interestingly, motor evoked potential recording was abnormal in only five patients. Further characteristic symptoms were psychomotor slowing (n = 9), often with speech disturbances such as decreased verbal fluency, and confusional state (n = 4). Visual or motor hemineglect (n = 5) as well as apraxia (n = 5) was confined to a few patients only. Pericallosal artery infarctions are a rare localization of stroke, mostly occurring as partial infarctions due to distal ACA pathology. Clinically, they are mainly characterized by hemiparesis predominately in the lower limb caused by involvement of supplementary motor cortex areas without affection of the corticospinal tract.

Predictors and early outcome of hemorrhagic transformation after acute ischemic stroke.

BACKGROUND: Hemorrhagic transformation (HT) after acute ischemic stroke is frequently detected using magnetic resonance imaging (MRI), in particular in patients treated with tissue plasminogen activator (tPA). Knowledge about causes and early clinical consequences of HT mostly arises from computed tomography-based studies. We analyzed potential predictors and early outcome of HT after stroke detected by MRI with T(2)*-weighted gradient echo sequences (T(2)*-MRI). METHODS: 122 consecutive stroke patients (mean age 65.5 years, 41% women) who underwent T(2)*-MRI within 6-60 h after stroke onset were included. 25.4% of patients were treated with tPA; the overall detection rate of HT on T(2)*-MRI was 20.5%. Potential predictors of HT, such as age, sex, blood pressure, stroke etiology, prior antithrombotic medication, neurological deficit on admission, tPA treatment, and specific MRI findings, were analyzed. In addition, we evaluated the effect of HT on early outcome: a decrease of >4 points on the National Institute of Health Stroke Scale (NIHSS) on day 5 was considered early improvement, and an increase of >4 points was considered early deterioration. RESULTS: The main predictor for occurrence of HT was tPA treatment (48.4 vs. 11.1%; odds ratio 7.50; 95% confidence interval 2.9-19.7; p < 0.001). Furthermore, the development of HT was associated with a severer neurological deficit on admission (mean NIHSS score 9.9 vs. 5.9; p = 0.003), and territorial infarction (88 vs. 58.8%; p = 0.007). 19 patients (15.6%) showed early improvement which was associated with the occurrence of HT (p = 0.011) and tPA treatment (p < 0.001). CONCLUSIONS: HT is a frequent finding on T(2)*-MRI in patients with acute ischemic stroke associated with tPA treatment, territorial infarction and severer neurological deficits on admission. However, HT does not cause clinical deterioration; it is rather related to a favorable early outcome likely reflecting early recanalization and better reperfusion in these patients.