A fast direct solver for surface-based whole-head modeling of transcranial magnetic stimulation.

When modeling transcranial magnetic stimulation (TMS) in the brain, a fast and accurate electric field solver can support interactive neuronavigation tasks as well as comprehensive biophysical modeling. We formulate, test, and disseminate a direct (i.e., non-iterative) TMS solver that can accurately determine global TMS fields for any coil type everywhere in a high-resolution MRI-based surface model with ~ 200,000 or more arbitrarily selected observation points within approximately 5 s, with the solution time itself of 3 s. The solver is based on the boundary element fast multipole method (BEM-FMM), which incorporates the latest mathematical advancement in the theory of fast multipole methods-an FMM-based LU decomposition. This decomposition is specific to the head model and needs to be computed only once per subject. Moreover, the solver offers unlimited spatial numerical resolution. Despite the fast execution times, the present direct solution is numerically accurate for the default model resolution. In contrast, the widely used brain modeling software SimNIBS employs a first-order finite element method that necessitates additional mesh refinement, resulting in increased computational cost. However, excellent agreement between the two methods is observed for various practical test cases following mesh refinement, including a biophysical modeling task. The method can be readily applied to a wide range of TMS analyses involving multiple coil positions and orientations, including image-guided neuronavigation. It can even accommodate continuous variations in coil geometry, such as flexible H-type TMS coils. The FMM-LU direct solver is freely available to academic users.

Adaptive short-term plasticity in the typical reading network.

The left temporo-parietal cortex (TPC) is crucial for phonological decoding, i.e., for learning and retaining sound-letter mappings, and appears hypoactive in dyslexia. Here, we tested the causal contribution of this area for reading in typical readers with transcranial magnetic stimulation (TMS) and explored the reading network's response with fMRI. By investigating the underlying neural correlates of stimulation-induced modulations of the reading network, we can help improve targeted interventions for individuals with dyslexia. 28 typical adult readers overtly read simple and complex words and pseudowords during fMRI after effective and sham TMS over the left TPC. To explore differences in functional activation and effective connectivity within the reading network, we performed univariate and multivariate analyses, as well as dynamic causal modeling. While TMS-induced effects on reading performance and brain activation showed large individual variability, multivariate analyses revealed a shift in activation in the left inferior frontal cortex for pseudoword reading after effective TMS. Furthermore, TMS increased effective connectivity from the left ventral occipito-temporal cortex to the left TPC. In the absence of effects on reading performance, the observed changes in task-related activity and the increase in functional coupling between the two core reading nodes suggest successful short-term compensatory reorganization in the reading network following TMS-induced disruption. This study is the first to explore neurophysiological changes induced by TMS to a core reading node in typical readers while performing an overt reading task. We provide evidence for remote stimulation effects and emphasize the relevance of functional interactions in the reading network.

A fast direct solver for surface-based whole-head modeling of transcranial magnetic stimulation.

Background: When modeling transcranial magnetic stimulation (TMS) in the brain, a fast and accurate electric field solver can support interactive neuronavigation tasks as well as comprehensive biophysical modeling. Objective: We formulate, test, and disseminate a direct (i.e., non-iterative) TMS solver that can accurately determine global TMS fields for any coil type everywhere in a high-resolution MRI-based surface model with ~200,000 or more arbitrarily selected observation points within approximately 5 sec, with the solution time itself of 3 sec. Method: The solver is based on the boundary element fast multipole method (BEM-FMM), which incorporates the latest mathematical advancement in the theory of fast multipole methods - an FMM-based LU decomposition. This decomposition is specific to the head model and needs to be computed only once per subject. Moreover, the solver offers unlimited spatial numerical resolution. Results: Despite the fast execution times, the present direct solution is numerically accurate for the default model resolution. In contrast, the widely used brain modeling software SimNIBS employs a first-order finite element method that necessitates additional mesh refinement, resulting in increased computational cost. However, excellent agreement between the two methods is observed for various practical test cases following mesh refinement, including a biophysical modeling task. Conclusion: The method can be readily applied to a wide range of TMS analyses involving multiple coil positions and orientations, including image-guided neuronavigation. It can even accommodate continuous variations in coil geometry, such as flexible H-type TMS coils. The FMM-LU direct solver is freely available to academic users.

Neonatal organ donation: Ethical insights and policy implications.

In the realm of clinical ethics as well as in health policy and organizational ethics, the onus of our work as ethicists is to optimize the medical care and experience of the patient to better target ethical dilemmas that develop in the course of care delivery. The role of ethics is critical in all aspects of medicine, but particularly so in the difficult and often challenging cases that arise in the care of pregnant women and newborns. One exemplary situation is that when a pregnant woman and her partner consider neonatal organ donation after receiving news of a terminal diagnosis and expected death of the newborn. While a newer, less practiced form of organ donation, this approach is gaining greater visibility as an option for parents facing this terminal outcome. The aim of our paper is to highlight some of the key ethical issues associated with neonatal organ donation and identify clinical and logistical aspects of implementing such an approach to facilitate organ donation.

[Treatment of proximal humeral fractures in Germany: Influence of the level of hospital care and the frequency of treatment]. / Behandlung proximaler Humerusfrakturen in Deutschland: Einfluss von Krankenhausversorgungsstufe und Behandlungsfrequenz.

BACKGROUND: Various treatment options exist for displaced proximal humeral fractures. The impact of the level of hospital care and frequency of treatment on current treatment regimens in Germany was analyzed. MATERIAL AND METHODS: A total of 576 hospitals were included. The survey covered questions on frequency, diagnostics, classification, therapy, complications, and clinical scenarios. RESULTS: In all, 48% of the hospitals returned the questionnaire: 73% treat more than 60% of the fractures surgically, mainly with angle-stable implants. The angle-stable plate is the treatment of choice for young patients, but older patients are treated using other treatment options. Problems and complications included malreduction, secondary displacement, screw perforation, avascular necrosis, and impingement. According to treatment indication, implant choice, and common complications, no significant differences between the level of hospital care and frequency of treatment were observed. CONCLUSION: Independent of the level of hospital care and frequency of treatment, there is a trend for head-preserving angular-stable surgery with a homogenous level of treatment in Germany.

The prevalence of human papilloma virus (HPV) infections in oral squamous cell carcinomas: a retrospective analysis of 88 patients and literature overview.

In addition to tobacco and alcohol consumption, the two main risk factors for oral squamous cell carcinoma (OSCC), recent studies have revealed infections with human papilloma virus (HPV) as an additional risk factor for OSCC development. In the field of head and neck malignancies, the prevalence of HPV infections in oropharyngeal cancer (OC) ranges in different studies up to 84%. While HPV infection is discussed as an independent risk factor in this region, its distinguished role in carcinogenesis of tumours localized to the oral cavity remains still uncertain. In this study, we analysed the HPV status in 88 consecutive patients with OSCCs localized anterior of the palatoglossal arch who were treated in the Department of Oral and Maxillofacial Surgery at the University Medical Center Mainz. The HPV status analysis was performed using DNA-PCR and immunostaining of p16 protein. The prevalence of HPV-positive OSCCs was about 6% (5 patients). In 3 patients the HPV subtypes 16/18 were found. No significant differences between the HPV positive and negative patients regarding age, gender, smoking and alcohol consumption, localization and TNM level could be detected. Contrary to other studies focussing on cancers of the lingual and palatine tonsil, the prevalence of HPV infections was much lower in the oral cavity. Therefore HPV infection might play a less important role in oral carcinogenesis.

[Evaluation of image quality of two different three-dimensional cone-beam-scanners used for orthopedic surgery in the bony structures of the pelvis in comparison with standard CT scans]. / Vergleich der Bildqualität zweier unterschiedlicher mobiler 3-dimensionaler Röntgen-C-Bögen mit einem konventionellen CT bei der Darstellung relevanter Strukturen am knöchernen Becken.

AIM: This study evaluated the image quality of two different cone beam CT scanners used in the operation theatre in pelvic trauma surgery in relation to their radiation dosage. Furthermore, the assumption that a higher dosage would result in better image quality was analysed by using the different acquisition scanner modes. MATERIAL AND METHODS: We scanned the acetabulum (n=4) and iliosacral joints (n=4) of two human cadavers with a conventional CT and with two mobile cone beam CT scanners (Siemens Arcadis Orbic 3D and Ziehm Vision Vario 3D). With the two cone beam CT scanners (3D-BV), we used 6 different acquisition modes with different radiation dosages. The axial views of all scans were exported and blinded. Subsequently, the images were evaluated by 7 medical doctors with regard to identifiability of cortical structures (acetabular joint, fovea capitis femoris, cortical bone of the femur head, iliosacral joint, and sacral foramina), and the quality of the cancellous structure of the femur head. The evaluation was performed on axial views by using a defined five-point score. The interrater quality was statistically analysed according to Cohen with the kappa coefficient. In addition, the Wilcoxon test was used to identify significances between the 21 paired results of the evaluators. For determination of the signal-to-noise ratio, a Catphan 600 reference block with two different test elements (Teflon, PMP) was used. RESULTS: Overall, the image quality of the conventional CT scans received the best score. Comparing the two 3D cone beams, the image quality of the Siemens Arcadis Orbic 3D in high-dosage mode received the best score (median: 2.40), the Ziehm Vision Vario 3D in low-dose mode without large patient key received the lowest score (median: 3.16). The differences in the 21 paired results of the two different acquisition modes were significant in 17 cases (p < 0.05) but the size of difference when comparing the different acquisition modes was almost always small. The interobserver agreement in one acquisition mode was low (kappa 0.008-0.134). The overall evaluation results of the same acquisition mode diverged by up to 2 score points. We noted a higher signal-to-noise ratio in the high dosage mode than in the low dosage mode. DISCUSSION: When using intraoperative 3D imaging with the cone beam CT technique for pelvic injury, image acquisition in low-dose mode is adequate in terms of signal-to-noise ratio and image quality. The image quality does not correlate linearly with a higher radiation dosage. Therefore, the pelvic trauma surgeon using this technique is encouraged to gather his own experience with low dose modes thereby reducing patient radiation exposure.

[Flexor tendon irritations after locked plate fixation of the distal radius with the 3.5 mm T-plate: identification of risk factors]. / Irritation der Beugesehnen nach palmarer winkelstabiler Plattenosteosynthese des distalen Radius mit der 3,5-mm-T-Platte: Erarbeitung von Risikofaktoren.

AIM: Volar locked plate fixation of distal radius fractures has become an established procedure in the past decade, although reports of flexor tendon injuries due to volar plating have been increasing. The aim of the present study is to identify the risk factors which produce irritations of flexor tendons using the locking palmar 3.5 mm T-plate, with special emphasis placed on the watershed line and the pronator quadratus muscle. METHOD: In this retrospective study, all patients with distal radius fractures who had been treated with a locking volar 3.5 mm T-plate between 2001 and 2005 were evaluated. The X-ray controls were analysed with regard to secondary losses of reduction, bony healing disturbances and the topographic relation to the watershed line. Follow-up included a clinical and subjective assessment using the DASH score. All patients underwent sonography to identify irritations of the tendons under functional conditions (neural and dorsal wrist flexion). RESULTS: A total of 151 patients were treated with the locked volar 3.5 mm T-plate. Of these, 68 patients could be included for follow-up. The mean age was 47.8 years with a mean follow-up period of 3.5 years. Fracture classification according to the AO indicated 13 A, 14 B and 41 C fractures with 37 Colles and 31 Smith fractures. Fracture union was achieved in all patients. A mean palmar tilt of 2.8 degrees (range: 1 to 9 degrees) was observed, with a loss of reduction in three cases of about 5 degrees. There were no implant failures. The mean DASH score was 12. The watershed line was reached by the distal edge of the plate in 48 patients and was exceeded in 20 cases. In 30 patients the pronator quadratus muscle could not be identified. In the remaining 38 cases the mean diameter was reduced to 1.4 mm, while the unaffected contralateral muscle had a mean diameter of 3.8 mm (range: 2.8 to 7 mm). Irritations of flexor tendons occurred only in 4 cases, in those patients where the pronator quadratus muscle could not be identified (2 tendon erosions and 2 tenosynovitises; 5.9%). Relevant functional distal plate prominence was detected in dorsal flexion (power grip) in 3 cases (4.4%), producing tendon deflection. The topographic relation of the plate to the watershed line played a minor role in causing tendon irritations, in contrast to the muscular coverage of the distal plate. Plate coverage by a vital reconstructed pronator quadratus muscle produces a greater distance of the tendon compartment to the plate, whereas a complete muscular coverage of the distal plate edge is difficult to realise, although it is not necessary regarding functional conditions. CONCLUSION: Stabilisation of distal radius fractures with dorsal and volar displacement by the locked palmar 3.5 mm T-plate produces positive results. A careful reconstruction of the pronator quadratus is more important than respecting the watershed line in that it achieves muscular coverage, and thus provides a greater distance of the plate to the tendon compartment. We recommend sonography after bony healing to identify functional plate prominence or tendon irritations under functional conditions (dorsal wrist flexion) and, if necessary, plate removal. Further systematic sonographic examinations should be undertaken including other locked plate systems.

[Rupture of the quadriceps tendon after lateral retinaculum release by arthroscopy]. / Quadrizepssehnenruptur nach arthroskopischem lateralem Retinakulumrelease.

Complications after arthroscopic surgery of the knee joint are infrequent. Quadriceps tendon ruptures after knee arthroscopy are rarities. Only two cases have been published in the medical literature. This article presents a case of a quadriceps tendon rupture that occurred in a 19-year-old patient 5 weeks after lateral release of the retinaculum by arthroscopy. The late occurrence differentiates this case from the other previously published cases.

[30 years of osteosynthesis: developments in surgical fracture treatment over the last three decades]. / 30 Jahre Osteosynthese : Entwicklung der operativen Knochenbruchbehandlung in den letzten drei Dekaden.

The primary objective of surgical fracture management by means of osteosynthesis used to be achieving the maximum fracture stability possible; this maxim has given way over time to a more biological approach. Advances in the technical development of implants, including their material properties, have created the conditions for osteosynthetic procedures with minimal soft tissue disruption. The technical conditions of modern external fixator systems allow an unlimited number of assemblies matched to the requirements of each individual patient. Special changes in plate holes and interlocking nails have increased the angular and axial stability of the assembly and are particularly suitable for fractures with inferior bone quality, for example in the case of osteoporosis. Navigated osteosynthetic procedures permit reliable and low-risk implantation of implants in anatomically challenging regions. Out of the sometimes distressing experiences of early osteosynthetic procedures where postoperative radiographs showed delayed or absent bone healing, grew the realisation that good vascularity of the soft tissues and bones is a prerequisite for good healing and a timely and favourable outcome. This means that in each individual case an appropriate implant and stabilization method should be selected by the surgeon, who is not only familiar with anatomy but also with soft-tissue-conserving (minimally invasive) operative techniques.

[Traumatic thoracic spine fractures: inter- and intraobserver reliability of vertebral, local and segmental kyphosis in lateral X-rays]. / Traumatische Brustwirbelfrakturen: Inter- und Intraobserver-Reliabilität der vertebralen, lokalen undsegmentalen Kyphose im seitlichen Röntgenbild.

BACKGROUND: The evaluation of the vertebral, local and segmental kyphosis according to Cobb is usual practice in the determination of traumatic, idiopathic and degenerative spinal deformities. The present study compares the inter- and intraobserver reliability of these 3 angles in the lateral X-rays of thoracic spine fractures with spinal kyphosis. METHODS: From 1999 till 2007 all patients with adequate X-rays, age < 50 years, traumatic, thoracic spine fracture, kyphotic deformity and surgical intervention were included. The vertebral, local and segmental kyphosis were assessed by 3 observers at 2 time-points in the preoperative lateral X-rays. RESULTS: 63 patients, 11 women and 52 men, with a mean age of 34 years could be evaluated. In all cases an adequate trauma had led to the fracture. The most common trauma was an injury with a motorcycle; the 12th thoracic vertebra was most commonly affected. The segmental kyphosis showed 'excellent' results for inter- and intraobserver reliability (Ø-ICC: 0.8189 and Ø-ICC:0.8003). 'Good' results for inter- and intraobserver reliability could be evaluated for the vertebral (Ø-ICC: 0.7797 and Ø-ICC: 0.7797) and local (Ø-ICC: 0.7532 and Ø-ICC: 0.7296) kyphosis. CONCLUSION: Due to excellent and good results for inter- and intraobserver reliability of the segmental,vertebral and local kyphosis in the lateral X-rays of the thoracic spine, these angles could be a helpful tool, indicating a surgical procedure in traumatic thoracic fractures with kyphosis. Further possible interesting applications in the usage of these 3 angles could be the observation of the vertebral sintering in surgically or conservatively treated vertebral fractures. Appropriate studies should be performed before general recommendations can be given.