bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of Post Deposition Annealing on Characteristics of HfxZr1-xO2
Authors: Triyoso Dina , Hegde Rama H. , Gregory Rich , Spencer Greg S. , Taylor William
Published: September 2009

In this paper the impact of post deposition annealing in various ambient on electrical properties of hafnium zirconate (HfxZr1-xO2) high-k dielectrics is reported. ALD HfxZr1-xO2 films are annealed in a nitrogen and/or oxygen ambient at 500°C to 1000°C. Devices annealed at 500°C in N2 has lower equivalent oxide thickness (EOT) of 10Å without significant increase in gate leakage (Jg), threshold voltage (Vt) and only a slight decrease in transconductance (Gm) values compared to 500°C O2 annealed devices. Furthermore, the impact of annealing HfxZr1-xO2 films in a reducing ambient (NH3) is studied. Optimized NH3 anneal on HfxZr1-xO2 results in lower CET, improved PBTI, low sub-threshold swing values, comparable high-field Gm with only a minor degradation in peak Gm compared to control HfxZr1-xO2. Finally, the impact of laser annealing vs. RTP annealed HfxZr1-xO2 films are reported. Laser annealing helped further stabilize tetragonal phase of HfxZr1-xO2 without inducing void formation. Good devices with low leakage, low EOT and high mobility are obtained for laser annealed HfxZr1-xO2.
Atomic Layer Deposition of Metal Oxide Films on GaAs (100) surfaces
Authors: Gougousi Theodosia , Lacis John W. , Hackley Justin C , Demaree John
Published: September 2009

Atomic Layer Deposition is used to deposit HfO2 and TiO2 films on GaAs (100) native oxides and etched surfaces. For the deposition of HfO2 films two different but similar ALD chemistries are used: i) tetrakis dimethyl amido hafnium (TDMAHf) and H2O at 275°C and ii) tetrakis ethylmethyl amido hafnium (TEMAHf) and H2O at 250°C. TiO2 films are deposited from tetrakis dimethyl amido titanium (TDMATi) and H2O at 200°C. Rutherford Back Scattering shows linear film growth for all processes. The film/substrate interface is examined using x-ray Photoelectron Spectroscopy and confirms the presence of an “interfacial cleaning” mechanism.
The Influence of Nitrogen Doping on the Chemical and Local Bonding Environment of Amorphous and Crystalline Ge2Sb2Te5
Authors: Washington Joseph , Joseph Eric A. , Paesler Michael A. , Lucovsky Gerald , Jordan-Sweet Jean L. , Raoux Simone , Chen Chieh-Fang , Pyzyna Adam , Dasaka Ravi K. , Lam Chung H. , Schrott Alejandro , Woicik Joseph C. , Ravel Bruce
Published: September 2009

Recent interest in phase change materials (PCMs) for non-volatile memory applications has been fueled by the promise of scalability beyond the limit of conventional DRAM and NAND flash memory [1]. However, for such solid state device applications, Ge2Sb2Te5 (GST), GeSb, and other chalcogenide PCMs require doping. Doping favorably modifies crystallization speed, crystallization temperature, and thermal stability but the chemical role of the dopant is not yet fully understood. In this work, X-ray Absorption Fine Spectroscopy (XAFS) is used to examine the chemical and structural role of nitrogen doping (N-) in as-deposited and crystalline GST thin films. The study focuses on the chemical and local bonding environment around each of the elements in the sample, in pre and post-anneal states, and at various doping concentrations. We conclude that the nitrogen dopant forms stable Ge-N bonds as deposited, which is distinct from GST bonds, and remain at the grain boundary of the crystallites such that the annealed film is comprised of crystallites with a dopant rich grain boundary.
Conventional vs Sustainable Transportation Fuels for the Future
Authors: Chianelli Russell R.
Published: September 2009

It is clear that in the next ten years major changes will be required in our liquids for transportation energy scenario. These changes are driven by two major factors. The first is the desire to achieve 'energy independence' and the second is the desire to achieve an 'environmentally friendly' fuel supply. These two forces will dominate energy research and development in the near future. This presupposes that the lack of viable hydrogen storage materials and the long-range electric vehicle materials will continue to be limiting the hydrogen and electric vehicle technology. The DOE recently reported that the available amounts of heavy hydrocarbons (tars, coal and shale oils) in North America (United States, Canada and Mexico) are sufficient for 500 years at current rates of usage. However, these sources must be converted to liquid transportation fuels in an environmentally favorable manner. Also, promising sources of sustainable liquid transportation fuels maybe found in growing algae and converting the contained lipids to biodiesel. In this presentation we discuss recent development in both areas that promise a smooth transition from conventional to the use of sustainable transportation fuel sources.
Current views on type 2 diabetes
Authors: Lin Yi , Sun Zhongjie
Published: September 2009

Type 2 diabetes mellitus (T2DM) affects a large population worldwide. T2DM is a complex heterogeneous group of metabolic disorders including hyperglycemia and impaired insulin action and/or insulin secretion. T2DM causes dysfunctions in multiple organs or tissues. Current theories of T2DM include a defect in insulin-mediated glucose uptake in muscle, a dysfunction of the pancreatic β-cells, a disruption of secretory function of adipocytes, and an impaired insulin action in liver. The etiology of human T2DM is multifactorial, with genetic background and physical inactivity as two critical components. The pathogenesis of T2DM is not fully understood. Animal models of T2DM have been proved to be useful to study the pathogenesis of, and to find a new therapy for, the disease. Although different animal models share similar characteristics, each mimics a specific aspect of genetic, endocrine, metabolic, and morphologic changes that occur in human T2DM. The purpose of this review is to provide the recent progress and current theories in T2DM and to summarize animal models for studying the pathogenesis of the disease.
Fuzzy waste load allocation model: a multiobjective approach
Authors: Ghosh Subimal , Mujumdar P. P.
Published: September 2009

Fuzzy Waste Load Allocation Model (FWLAM), developed in an earlier study, derives the optimal fractional levels, for the base flow conditions, considering the goals of the Pollution Control Agency (PCA) and dischargers. The Modified Fuzzy Waste Load Allocation Model (MFWLAM) developed subsequently is a stochastic model and considers the moments (mean, variance and skewness) of water quality indicators, incorporating uncertainty due to randomness of input variables along with uncertainty due to imprecision. The risk of low water quality is reduced significantly by using this modified model, but inclusion of new constraints leads to a low value of acceptability level, λ, interpreted as the maximized minimum satisfaction in the system. To improve this value, a new model, which is a combination of FWLAM and MFWLAM, is presented, allowing for some violations in the constraints of MFWLAM. This combined model is a multiobjective optimization model having the objectives, maximization of acceptability level and minimization of violation of constraints. Fuzzy multiobjective programming, goal programming and fuzzy goal programming are used to find the solutions. For the optimization model, Probabilistic Global Search Lausanne (PGSL) is used as a nonlinear optimization tool. The methodology is applied to a case study of the Tunga–Bhadra river system in south India. The model results in a compromised solution of a higher value of acceptability level as compared to MFWLAM, with a satisfactory value of risk. Thus the goal of risk minimization is achieved with a comparatively better value of acceptability level.
An alternative approach for investigation of the wave-induced scour around pipelines
Authors: Kazeminezhad M. H. , Etemad-Shahidi A. , Yeganeh Bakhtiary A.
Published: September 2009

Scour around submarine pipelines remains a largely complex and not yet fully understood problem. In this study, wave-induced scour around submarine pipelines was investigated. Since various physical processes occur during the development of a scour hole, the effects of each process were considered by employing several nondimensional parameters. To find the effective parameters on equilibrium scour depth, the correlation between independent parameters (e.g. Keulegan–Carpenter number) and dependent parameter (nondimensional scour depth) were determined using different experimental data. Then, an Artificial Neural Network (ANNs) approach was used to develop a more accurate model for prediction of wave-induced scour depth around submarine pipelines. ANN models with different input parameters including gap to diameter ratio, Keulegan–Carpenter number, pipe Reynolds number, Shields number, sediment Reynolds number and boundary layer Reynolds number were trained and evaluated to find the best predictor model. To develop the ANN models, both holdout and tenfold cross-validation methods were used. In addition, an existing empirical method was examined. Results show that the empirical method has a significant error in the prediction of scour depth for the cases with an initial gap between pipe and seabed. It is also indicated that the ANN models outperform the empirical method in terms of prediction capability.
Neuro-fuzzy modeling for level prediction for the navigation sector on the Magdalena River (Colombia)
Authors: Fernández Nelson , Jaimes William , Altamiranda Edmary
Published: September 2009

The variations associated with level changes and the state of the channel in the Magdalena River in Colombia (South America) frequently affect the navigation possibilities for boats and ferries, which cause high costs for their users. For this reason, this work presents a bio-inspired model to support the decision-making concerning the navigation using a neuro-fuzzy approach developed in previous works with a novel application. Considering the average daily levels of the river registered by the limnigraphical stations from the Colombian Institute for Hydrological, Meteorology and Environmental Studies (IDEAM), during the time period between 1998 and 2003 for the Puerto Salgar, Puerto Berrio, El Banco and Calamar locations, it was possible to design and establish a neuro-fuzzy hydrological model to predict with great precision the level of water in the river for the route of navigation, allowing the appropriate decision-making for Magdalena River operators to pre-determine the weight of shipment for any boat or ferry on their route. The developed model showed better performance for the forecasting than the previously established deterministic models for this specific application.
Methylene blue removal from contaminated waters using O3, natural zeolite, and O3/zeolite
Authors: Valdés H. , Tardón R. F. , Zaror C. A.
Published: September 2009

This paper compares experimental results on methylene blue (MB) removal systems based on ozone oxidation, zeolite adsorption, and simultaneous adsorption-oxidation using ozone in the presence of natural zeolite. The effect of pH (2–8), and the presence of radical scavengers (sodium acetate) on process rates and removal efficiencies are assessed at laboratory scale. The experimental system consisted of a 1 L differential circular flow reactor and an ozone generator rated at 5 g O3/h. Results show that ozone oxidation combined with zeolite adsorption increases the overall MB oxidation rate with respect to ozonation process and zeolite adsorption. In presence of free radical scavenger, only a 25% of reduction on MB removal rate are observed in the simultaneous treatment, as compared with 70% when ozonation treatment is used, suggesting that MB oxidation reactions take mainly place on the zeolite surface.
Road runoff management using over-the-shoulder infiltration: real-scale experimentation
Authors: Piguet P. , Parriaux A. , Bensimon M.
Published: September 2009

A new management policy regarding road runoff was proposed in 2002 by the Swiss Federal Office for the Environment (FOEN). This new concept is based on the diffuse infiltration of road runoff into embankment slopes, where soils will filter particles and contaminants. The shoulder lying between road surface and infiltration slopes must be impervious in order to maximise the amount of water reaching the slope and avoid losses in the road structure. The implementation of this new concept should lower the impact of roads on the environment, improve aquifer recharge and reduce construction costs. The Swiss Federal Road Office (FedRO) decided to carry out real-scale investigations regarding this new policy and thus commissioned the GEOLEP to design, build, and test 5 different shoulder structures. This paper presents the results of a 2-years survey of infiltration processes in these shoulders to establish the best performing structure. The first three shoulders were overlaid with 5 cm of gravel mixed with humus, gravel mixed with clay, and seeded with lawn, respectively. The latter two had impervious layers located 26 cm deep: the road bituminous basement (road base) was prolonged and coated with bitumen in the first case, and a sodic-bentonite geotextile was used in the second. Both were covered with gravel. All shoulders were equipped with basal collecting devices that measured hydraulic fluxes seeping through the shoulders. In total, 112 natural precipitations and 3 artificial events were monitored. Artificial events mimicked known transitory regimes (thunderstorms) or were performed with constant regime. The goal was to effectively assess infiltration processes in shoulders. Results showed that shoulders made of gravel and humus or lawn were highly ineffective (only 30 to 40% of runoff is conducted to the infiltration slope). Gravel and clay was more efficient with a proportion of approximately 60%. The shoulder with prolonged road base showed similar results since the bituminous coating was in fact rather permeable. The best results were exhibited by the shoulder waterproofed with bentonitic geotextile, which allowed no water to penetrate. This material already proved to be very powerful in groundwater catchments. The authors thus proposed a combination of sodic-bentonite geotextile covered by a gravel and clay mixture. This would be the most efficient shoulder: it will convey all the runoff to infiltration slopes, thereby optimising its filtration, which in turn will enhance environmental conditions in the vicinity of roads.
Bioaerosol in Composting Facilities: Occupational Health Risk Assessment
Authors: Schlosser Olivier , Huyard Alain , Cartnick Keith , Yañez Adela , Catalán Vicente , Do Quang Zdravka
Published: September 2009

This research found evidence of an association between occupational exposure to bioaerosols in composting plants and health outcome occurrence in exposed workers. An occupational exposure assessment in six composting plants was performed to better characterize personal exposure levels and evaluate associated health risk in workers. Sampling results showed large ranges of concentrations of dust, bacteria, molds, and endotoxin in ambient air and in personal samples, both when driving a front‐end loader and when cleaning, monitoring, and performing maintenance tasks. Mean personal exposure levels were high at 100 to more than 10 000 times higher than outdoor background levels and fully consistent with occurrence of inflammatory and allergic respiratory outcomes among workers. Engineering control, personal protection, and education and training programs for employees, health, and safety officials, and occupational physicians are being developed and implemented.
Updated Activated Sludge Model n°1 Parameter Values for Improved Prediction of Nitrogen Removal in Activated Sludge Processes: Validation at 13 Full‐scale Plants
Authors: Choubert Jean‐Marc , Stricker Anne‐Emmanuelle , Marquot Aurélien , Racault Yvan , Gillot Sylvie , Héduit Alain
Published: September 2009

The Activated Sludge Model n°1 (ASM1) is the main model used in simulation projects focusing on nitrogen removal. Recent laboratory‐scale studies have found that the default values given 20 years ago for the decay rate of nitrifiers and for the heterotrophic biomass yield in anoxic conditions were inadequate. To verify the relevance of the revised parameter values at full scale, a series of simulations were carried out with ASM1 using the original and updated set of parameters at 20°C and 10°C. The simulation results were compared with data collected at 13 full‐scale nitrifying‐denitrifying municipal treatment plants. This work shows that simulations using the original ASM1 default parameters tend to overpredict the nitrification rate and underpredict the denitrification rate. The updated set of parameters allows more realistic predictions over a wide range of operating conditions.
Integrating Mental Health in Welfare Evaluation: An Empirical Application
Authors: Das Sanghamitra , Mukhopadhyay Abhiroop , Ray Tridip
Published: September 2009

This paper presents simple measures of individual and family mental health indices based on axiomatic foundations and integrates mental health into a neoclassical model that allows for proper substitution possibilities in the family preferences and quantifies its significance in family utility. We find that mental health effects are far more important than the effect of consumption or children's schooling in determining family utility. We illustrate the usefulness of our approach by considering the case of HIV/AIDS experience in India. Using our approach, we find that while there are no significant differences in per capita consumption and schooling between HIV and NON HIV families, the welfare loss from HIV/AIDS are still considerably large due to the inclusion of mental health. Integrating mental health in a utility maximization framework helps us quantify this welfare loss.
First experiences with an adjustable gravitational valve in childhood hydrocephalus
Authors: Rohde Veit , Haberl Ernst-Johannes , Ludwig Hans , Thomale Ulrich-W.
Published: September 2009

Object

The goal of this report was to describe the authors' initial experiences with an adjustable gravity-assisted valve (GAV) called the ProGAV in treating childhood hydrocephalus.

Methods

The ProGAV was implanted in 53 children (29 boys and 24 girls, median age 7.3 years) with hydrocephalus of various origins. The ProGAV consists of a differential-pressure unit with adjustable opening pressures and a gravitational unit with a fixed opening pressure.

Results

The mean follow-up period was 15.2 months (range 6–44 months). The authors did not observe any valve-related complications. Four infections (7.5%) occurred, warranting the removal of the shunt. In 19 children, the opening pressure was changed at least once during the follow-up period, for underdrainage in 10, overdrainage in 8, and shunt weaning in 1, with substantial clinical improvement in 18 children. Overall, good clinical results were obtained in 47 (88.7%) of the 53 valve placements.

Conclusions

With an overall success rate of 88.7%, the first experiences with the ProGAV in childhood hydrocephalus are promising and justify its further use in the pediatric population.
Medial pectoral nerve to musculocutaneous nerve neurotization for the treatment of persistent birth-related brachial plexus palsy: an 11-year institutional experience
Authors: Wellons John C. , Tubbs R. Shane , Pugh Jeffrey A. , Bradley Nadine J. , Law Charles R. , Grabb Paul A.
Published: September 2009

Object

Medial pectoral nerve (MPN) to musculocutaneous nerve (MCN) neurotization for recovery of elbow flexion by biceps reinnervation is a valid option following traumatic injury to the upper brachial plexus. A major criticism of the application of this technique in infants is the smaller size of the MPN and mismatch of viable axons. We describe our institutional experience utilizing this procedure and critically examine functional outcomes.

Methods

Office charts and hospital records of children from over an 11-year period beginning January 1997 were reviewed. Of the 53 children of various ages undergoing brachial plexus exploration for traumatic injury of any nature, 20 underwent MPN to MCN neurotization as a part of an overall procedure in the first year of life to treat birth-related brachial plexus palsy and had at least 9 months' follow-up. Medial pectoral nerve to MCN neurotization was chosen if the results of clinical examination and intraoperative electrophysiological evidence were consistent with medial cord function. Functional recovery was defined as the ability of the child to bring their hand to their mouth.

Results

Sixteen patients (80%) gained functional recovery. The median age at surgery was 7 months. Median time to first clinic visit documenting recovery was 11.5 months and median overall follow up was 21.5 months. Preoperative hand function was a useful predictor of recovery of elbow flexion.

Conclusions

Medial pectoral nerve to MCN neurotization is a valid surgical option for the reinnervation of the biceps muscle for birth-related brachial plexus palsy when the hand is functional preoperatively. Useful elbow flexion can be expected in the majority of these children.
Periosteal chondroma of the pediatric cervical spine
Authors: Fahim Daniel K. , Johnson Keyne K. , Whitehead William E. , Curry Daniel J. , Luerssen Thomas G. , Jea Andrew
Published: September 2009

Periosteal chondromas located in the spine are rare. The authors document an even more infrequent occurrence of a recurrent periosteal chondroma in the cervical spine of a 6-year-old boy. During the operation, a giant (> 7 cm in diameter) periosteal chondroma with involvement of the C-5 and C-6 vertebral bodies was resected. The vertebral column was reconstructed with anterior-posterior instrumentation. The pathological examination revealed that the tumor consisted of chondroid tissue with typical chondrocytes, confirming the diagnosis of periosteal chondroma.
Transtubular microendoscopic approach for resection of a choroidal arteriovenous malformation
Authors: Fahim Daniel K. , Relyea Katherine , Nayar Vikram V. , Fox Benjamin D. , Whitehead William E. , Curry Daniel J. , Luerssen Thomas G. , Jea Andrew
Published: September 2009

The authors describe the novel use of a table-mounted tubular retractor system (MetRx) originally designed for minimally invasive spine surgery, in the resection of an intraventricular arteriovenous malformation (AVM) in a 12-year-old child. The tubular retractor system may have several advantages over traditional Greenberg or Leyla retractors in selected intracranial procedures. In our case, the low-profile 4 × 22–mm tube and fixed table attachment offered excellent exposure of the trigone of the lateral ventricle where the choroidal AVM was located and from which it was completely resected. Immediate postoperative cerebral angiography confirmed that the entire AVM had been resected. The patient suffered no new neurological deficits as a result of the retractor system or the exposure that it afforded. Although the good clinical results of a single case cannot be directly compared with those obtained using other open techniques of intracranial surgery in larger series, microendoscopic surgery of the brain is an alternative to the other techniques and may be recommended as a time-saving, trauma-reducing procedure with the potential to improve postoperative outcomes.
Treatment of diffuse intrinsic brainstem gliomas: failed approaches and future strategies
Authors: Frazier James L. , Lee James , Thomale Ulrich W. , Noggle Joseph C. , Cohen Kenneth J. , Jallo George I.
Published: September 2009

Diffuse intrinsic pontine gliomas constitute ~ 60–75% of tumors found within the pediatric brainstem. These malignant lesions present with rapidly progressive symptoms such as cranial nerve, long tract, or cerebellar dysfunctions. Magnetic resonance imaging is usually sufficient to establish the diagnosis and obviates the need for surgical biopsy in most cases. The prognosis of the disease is dismal, and the median survival is < 12 months. Resection is not a viable option. Standard therapy involves radiotherapy, which produces transient neurological improvement with a progression-free survival benefit, but provides no improvement in overall survival. Clinical trials have been conducted to assess the efficacy of chemotherapeutic and biological agents in the treatment of diffuse pontine gliomas. In this review, the authors discuss recent studies in which systemic therapy was administered prior to, concomitantly with, or after radiotherapy. For future perspective, the discussion includes a rationale for stereotactic biopsies as well as possible therapeutic options of local chemotherapy in these lesions.
Neck injuries in young pediatric homicide victims
Authors: Brennan Laura K. , Rubin David , Christian Cindy W. , Duhaime Ann-Christine , Mirchandani Haresh G. , Rorke-Adams Lucy B.
Published: September 2009

Object

In this study, the authors estimate the prevalence of injuries to the soft tissue of the neck, cervical vertebrae, and cervical spinal cord among victims of abusive head trauma to better understand these injuries and their relationship to other pathophysiological findings commonly found in children with fatal abusive head trauma.

Methods

The population included all homicide victims 2 years of age and younger from the city of Philadelphia, Pennyslvania, who underwent a comprehensive postmortem examination at the Office of the Medical Examiner between 1995 and 2003. A retrospective review of all available postmortem records was performed, and data regarding numerous pathological findings, as well as the patient's clinical history and demographic information, were abstracted. Data were described using means and standard deviations for continuous variables, and frequency and ranges for categorical variables. Chi-square analyses were used to test for the association of neck injuries with different types of brain injury.

Results

The sample included 52 children, 41 (79%) of whom died of abusive head trauma. Of these, 29 (71%) had primary cervical cord injuries: in 21 there were parenchymal injuries, in 24 meningeal hemorrhages, and in 16, nerve root avulsion/dorsal root ganglion hemorrhage were evident. Six children with abusive head trauma had no evidence of an impact to the head, and all 6 had primary cervical spinal cord injury (SCI). No child had a spinal fracture. Six of 29 children (21%) with primary cervical SCIs had soft-tissue (ligamentous or muscular) injuries to the neck, and 14 (48%) had brainstem injuries. There was a significant association of primary cervical SCI with cerebral edema (p = 0.036) but not with hypoxia-ischemia, infarction, or herniation.

Conclusions

Cervical SCI is a frequent but not universal finding in young children with fatal abusive head trauma. In the present study, parenchymal and/or root injury usually occurred without evidence of muscular or ligamentous damage, or of bone dislocation or fracture. Moreover, associated brainstem injuries were not always seen. Although there was a significant association of primary cervical cord injury with cerebral edema, there was no direct relationship to brainstem herniation, hypoxia-ischemia, or infarction. This suggests that cervical spinal trauma is only 1 factor in the pathogenesis of these lesions.
Primary closure of large thoracolumbar myelomeningocele with bilateral latissimus dorsi flaps
Authors: Hosseinpour Mehrdad , Forghani Siamak
Published: September 2009

Object

Myelomeningocele (MMC) is the most complex congenital malformation of the CNS that is compatible with life. Different closure techniques are available for defect reconstruction, but wound healing and tension-free closure of the skin in the midline remain major considerations in large MMCs. In this study, the authors used bilateral proximally based latissimus dorsi (LD) skin island muscle pedicle flaps for closure of large thoracolumbar MMC defects.

Methods

Twenty infants with very large thoracolumbar MMCs were enrolled in the study. The mean of age of the patients was 4.1 ± 2.3 months. The width of the MMC was 6 ± 1.2 cm. At operation, 2 triangular V-Y flaps were designed on each side of the defect; the tip of the triangle was extended to the posterior axillary line. The LD flaps based on the thoracodorsal arteries were elevated bilaterally and advanced toward the midline with moderate tension and sutured together. Postoperatively, infants were positioned prone for 7 days and discharged on the 8th day after the operation. They were followed every 2 weeks for evaluation of wound healing.

Results

The wounds healed without any major complication. There was no dehiscence in the postoperative period.

Conclusions

The authors recommended bilateral superiorly based LD skin flaps as an effective method for closure of large thoracolumbar MMC defects. Neural tube defects are among the most common of all human birth defects.
Clinical practice guidelines
Authors: Vachhrajani Shobhan , Kulkarni Abhaya V. , Kestle John R. W.
Published: September 2009

In the era of evidence-based medicine, clinical practice guidelines (CPGs) have become an integral part of many aspects of medical practice. Because practicing neurosurgeons rarely have the time or, in some cases, the methodological expertise, to assess and assimilate the totality of primary research, CPGs can in theory provide a vehicle through which neurosurgeons could more efficiently integrate the most current evidence into patient management. Clinical practice guidelines have been met with some skepticism, however, particularly within the neurosurgical community. Some have expressed concerns that the promise of CPGs has not been matched by the reality. Others who oppose CPGs fear that they hinder the art of medicine, and limit physician and patient autonomy. The purpose of this paper is to provide the practicing neurosurgeon with an up-to-date review of CPGs. The authors discuss some of the complexities and recent advancements in CPG development, appraisal, and publication. An overview of the various systems for grading medical evidence and issuing CPG recommendations, each of which has its advantages and disadvantages, is included, and the current knowledge on the impact of CPGs in 2 important realms, patient care and medicolegal issues, is discussed.

The purpose of this review is to provide a balanced, current synopsis of what CPGs are, how they are developed, and what they can and cannot do. The authors hope that this will allow neurosurgeons to make more informed decisions about the many CPGs that will inevitably become an essential component of medical practice in the years to come.
Management of a locked Strata valve
Authors: Bullivant Kelly J. , Mitha Alim P. , Hamilton Mark G.
Published: September 2009

The PS Medical Strata valve is a programmable shunt valve used in the treatment of hydrocephalus that allows for noninvasive changes in the pressure setting using a magnet. The Strata valve is sensitive to magnetic fields, and reprogramming is frequently necessary after MR imaging. A known but rare complication of the Strata valve is that the rotor can become locked, causing shunt malfunction. This complication can only occur in a first generation Strata valve.
Electromagnetic-guided neuroendoscopy in the pediatric population
Authors: Sangra Meharpal , Clark Simon , Hayhurst Caroline , Mallucci Conor
Published: September 2009

Object

Image-guided neuroendoscopy is being increasingly used in an attempt to reduce the morbidity associated with surgery and to make navigation easier. It has a particularly useful application in the pediatric population for the treatment of conditions such as complex hydrocephalus and arachnoid cysts. However, its use has been limited by the requirement for rigid head fixation, which may be difficult in infants because of the immaturity of the skull. In addition there can be line-of-sight issues, which can be a problem with optical-based systems. Electromagnetic navigation has eliminated the requirement for head immobilization, and its successful use in the infant population has been reported. The authors present their series to date, define its role, and discuss its advantages over other forms of image-guided navigation.

Methods

The authors used the electromagnetic StealthStation and software (Medtronic) for neuronavigation. A dynamic reference frame was attached to the head using an adhesive dressing. The patient was positioned without rigid fixation and was registered using a specially designed stylet. Navigation was through a stylet, which could be placed within the endoscope. Direct advantages were no rigid head fixation, the ability to maneuver the endoscope without the requirement for a bulky optical attachment, and no loss of navigation caused by user obstruction of reflective fiducial markers. The authors performed a total of 28 procedures in 23 patients. There were 9 arachnoid cyst marsupializations, 4 multiple fenestrations for multiloculated hydrocephalus, 4 aqueductal stenting procedures for encysted fourth ventricles, 5 endoscopic third ventriculostomies, 3 septum pellucidotomies, 2 tumor biopsies, and 1 tumor cyst decompression.

Results

Electromagnetic navigation was successful in all cases. Two complications were reported: a subdural collection, requiring bur hole drainage after a successful fenestration of the arachnoid cyst and failed treatment of complex hydrocephalus requiring subsequent placement of a ventriculoperitoneal shunt.

Conclusions

The electromagnetic technology provides reliable image-guided endoscopy. It has several advantages over alternative forms of stereotaxy, and the ability to use it without the need for rigid head fixation makes it eminently suitable for the pediatric population. Its use and application in the treatment of a variety of different conditions has been demonstrated successfully.
Acute subdural hematoma secondary to distal middle cerebral artery aneurysm rupture in a newborn infant
Authors: Iza-Vallejo Begoña , Mateo-Sierra Olga , Fortea-Gil Fernando , Ruiz-Juretschke Fernando , Martín Yolanda Ruiz
Published: September 2009

The authors present the case of a peripheral aneurysmal lesion that developed in a newborn baby and was successfully treated by endovascular parent artery occlusion. Given the natural history of aneurysms, which are prone to rupture and to cause deleterious intracerebral hemorrhage, with high mortality rates, aggressive and early management (endovascular or surgical) is recommended.
Linear vein–based arteriovenous malformations in children
Authors: Maher Cormac O. , Scott R. Michael
Published: September 2009

Object

The authors reviewed the experience of a single surgeon in the surgical treatment of arteriovenous malformations (AVMs) in children, with specific attention to the angioarchitectural appearance of these lesions.

Methods

The authors performed a retrospective review of pediatric cases of AVM treated at a single institution over a 15-year period. Inclusion criteria consisted of pediatric age at time of treatment and resection of a pial AVM. The AVMs were considered linear-based if they had a single, centrally located, dominant vein with a linear configuration rather than the typical central nidus.

Results

Sixty-seven patients, ranging in age from 6 months to 17 years, underwent surgical treatment of an AVM between January 1, 1990, and December 30, 2005. In these patients, 31 AVMs (46%) had a distinct linear configuration that was centered on a dominant draining vein (“vein-based”). These AVMs presented with hemorrhage (61%), incidental findings on imaging (16%), or seizures (13%). In 4 cases, AVM recurrence was noted on angiographic follow-up after postoperative angiography showed no residual lesion. Recurrence was seen at 1 year in 2 cases, and at 3 and 11 years in 1 case each.

Conclusions

A linear vein–based morphological pattern is common in pediatric AVMs and may recapitulate the embryological origins of the cerebral circulation. Surgical treatment in these cases can also be vein-based, through a narrow surgical corridor, which leads to minimal cortical disruption.
Neuronavigation-guided implantation of foramen ovale electrodes in a child
Authors: Daszkiewicz Paweł , Zwoliński Piotr , Roszkowski Marcin
Published: September 2009

The purpose of this paper is to present a novel technique of implantation of foramen ovale electrodes under neuronavigation guidance. The technique is simple, safe, and effective, greatly reducing the patient's trauma, the operating time, and the surgeon's stress.
Ultrasound-aided fixation of a biodegradable cranial fixation system: uses in pediatric neurosurgery
Authors: Aldana Philipp R. , Roy Saswata , Postlethwait Richard A. , James Hector E.
Published: September 2009

Object

Bioresorbable implant systems have been used in neurosurgery for the rigid fixation of cranial and facial bones. A relatively recent advancement has been the fixation of these implants using an ultrasonic device. The experience with such a device in neurosurgical practice has been limited. The authors report on their experience with ultrasound-aided fixation of bioresorbable implants in pediatric neurosurgical practice.

Methods

The study consisted of 2 parts. The retrospective portion consisted of a chart review of pertinent clinical information, complications, and outcomes after the use of a commercially available ultrasound-aided bioresorbable implant system (SonicWeld Rx, KLS Martin L.P.). Follow-up was obtained in all patients via clinical examination or telephone interview. The prospective portion of the study consisted of video analysis of the implantation technique in a routine craniotomy. Implantation times were measured, and delays during treatment were noted.

Results

Over a period of 2 years, 28 consecutive patients underwent placement of these implants for bone fixation during craniotomies or craniofacial reconstructions. The only complication was seen in a child with Crouzon syndrome, who had a wound infection caused by Serratia sepsis from a central venous line infection. There were no repeated operations for implant-related swelling, and no cases of premature plate resorption, bone instability, or settling. In vivo, the average time required to implant a resorbable pin with this system was 22 seconds.

Conclusions

The use of a bioresorbable implant system with ultrasound-aided pin fixation in pediatric neurosurgery cases achieved adequate stability with few complications. This system was easy to use and provided rapid fixation of implants.
Endovascular treatment of a fusiform basilar artery aneurysm using multiple “in-stent stents”
Authors: Crowley R. Webster , Evans Avery J. , Kassell Neal F. , Jensen Mary E. , Dumont Aaron S.
Published: September 2009

Fusiform aneurysms of the basilar artery present difficult challenges for the treating physician. On one hand, these aneurysms are difficult and dangerous to treat. On the other, the relatively high rupture rate, risk of thromboemboli, and the frequent presence of mass effect on the brainstem often demand treatment rather than observation. While conservative treatment may be reasonable in an elderly patient, the relative resiliency and the larger lifetime cumulative risks of pediatric patients are compelling arguments for treatment. With the advancement of endovascular techniques some of these lesions have become treatable without the high morbidity and mortality rates associated with open surgical treatment, albeit with risks of their own. The authors present the case of a fusiform aneurysm arising from a severely tortuous basilar artery in a 22-month-old boy. The aneurysm was successfully treated using flow diversion by placing multiple intracranial stents without coil embolization. This allowed for thrombosis of the aneurysm and resolution of the mass effect on the brainstem without compromising blood flow to the brainstem.
Predictors of tumor progression among children with gangliogliomas
Authors: Khashab Mostafa El , Gargan Lynn , Margraf Linda , Koral Korgun , Nejat Farideh , Swift Dale , Weprin Bradley , Bowers Daniel C.
Published: September 2009

Object

Few reports describe the outcome and prognostic factors for children with gangliogliomas. The objective of this report was to describe the progression-free survival (PFS) for children with low-grade gangliogliomas and identify risk factors for tumor progression.

Methods

A retrospective study was performed in children with low-grade gangliogliomas who were evaluated and treated in the neuro-oncology department between 1986 and 2006 to determine risk factors for subsequent tumor progression.

Results

A total of 38 children with newly diagnosed gangliogliomas were included in this report. Thirty-four children were treated with surgery alone, 3 with subtotal resection and radiation therapy, and 1 with subtotal resection and chemotherapy. The follow-up ranged from 4 months to 15.8 years (mean 5.7 ± 4.2 years [± SD]). Seven children have experienced tumor progression, and 1 child died after his tumor subsequently underwent malignant transformation. The 5-year PFS was calculated to be 81.2% using Kaplan-Meier survival analysis. Initial presentation with seizures (p = 0.004), tumor location in the cerebral hemisphere (p = 0.020), and complete tumor resection (p = 0.035) were associated with prolonged PFS. Further analysis of the above significant variables by a Cox regression model identified initial presentation with seizures as being associated with prolonged PFS (p = 0.028).

Conclusions

The PFS and overall survival of children with gangliogliomas are good. Tumors located in the cerebral hemispheres, the achievement of total resection, and seizures at presentation were associated with prolonged PFS. Cox regression analysis identified presenting symptoms including seizures as significant predictive factors of PFS. Prospective studies with larger numbers of children are needed to define the significant factors of tumor progression.
Extraventricular subependymal giant cell tumor in a child with tuberous sclerosis complex
Authors: Bollo Robert J. , Berliner Jonathan L. , Fischer Ingeborg , Miles Daniel K. , Thiele Elizabeth A. , Zagzag David , Weiner Howard L.
Published: September 2009

Subependymal giant cell tumors (SGCTs) are observed in 5–20% of patients with tuberous sclerosis complex (TSC) but account for ~ 25% of neurological morbidity. The authors report the case of a 7-year-old girl with TSC and multiple cortical tubers who presented with worsening seizures in the context of the rapid growth of a cystic, calcified, extraventricular SGCT in the right frontal lobe, initially thought to represent a cortical tuber. The tumor and surrounding tubers were excised, and clinical seizures resolved. This is the first report of an extraventricular SGCT in a child with TSC outside the neonatal period.
Outcome of ventriculoperitoneal shunt placement in Grade IV tubercular meningitis with hydrocephalus: a retrospective analysis in 95 patients
Authors: Srikantha Umesh , Morab Jagadeesh V. , Sastry Savitr , Abraham Rojin , Balasubramaniam Anandh , Somanna Sampath , Devi Indira , Bangalore Chandramouli A. , Pandey Paritosh
Published: September 2009

Object

Hydrocephalus is the most common complication of tubercular meningitis (TBM). Relieving hydrocephalus by ventriculoperitoneal (VP) shunt placement has been considered beneficial in patients in Palur Grade II or III. The role of VP shunt placement in those of Grade IV is controversial and the general tendency is to avoid its use. Some authors have suggested that patients in Grade IV should receive a shunt only if their condition improves with a trial placement of an external ventricular drain (EVD). In the present study, the authors assessed the outcome of VP shunt placement in patients in Grade IV TBM with hydrocephalus to examine the factors predicting outcome and to determine whether a trial with an EVD is absolutely necessary prior to shunt placement.

Methods

Ninety-five consecutive cases of TBM with hydrocephalus in which the patients underwent VP shunt placement were retrospectively analyzed, and direct VP shunts were placed whenever possible. An EVD was placed first only in the presence of deranged blood parameters. Outcomes were assessed both in the short and long term.

Results

The mean patient age was 17.5 years (range 1–55 years). Fifty-two patients underwent direct VP shunt placement, and the remaining 43 received EVDs first. Overall, 33 and 45% of patients had favorable short- and long-term outcomes, respectively. Age older than 3 years and duration of altered sensorium ≤ 3 days were predictive of a favorable short-term outcome. Glasgow Coma Scale score at presentation was predictive of long-term outcome. Of the patients who did not improve with placement of an EVD prior to VP shunt insertion, 24 and 18% had favorable short- and long-term outcomes, respectively; this was not significantly different from the outcome in the patients who underwent direct VP shunt placement.

Conclusions

Direct VP shunt placement is an effective option in patients with Grade IV TBM with hydrocephalus. Age and duration of altered sensorium are predictive of short-term outcome, while Glasgow Coma Scale score at presentation predicts long-term outcome. Ventriculoperitoneal shunts should be considered even in patients who do not improve with an EVD.
Sporadic unilateral vestibular schwannoma in the pediatric population
Authors: Walcott Brian P. , Sivarajan Ganesh , Bashinskaya Bronislava , Anderson Douglas E. , Leonetti John P. , Origitano Thomas C.
Published: September 2009

Object

Vestibular schwannomas (VSs) are rare in the pediatric population. Most often, these lesions manifest as a bilateral disease process in the setting of neurofibromatosis Type 2. Even in the absence of additional clinical diagnostic criteria, the presentation of a unilateral VS in a young patient may be a harbinger of future penetrance for this hereditary tumor syndrome.

Methods

The authors retrospectively reviewed the charts of a cohort of 7 patients who presented with apparently sporadic, unilateral VSs. These patients had previously undergone surgery via translabyrinthine, retrosigmoid, or combined approaches. Clinical outcomes were reviewed with emphasis on facial nerve function and follow-up for signs and symptoms of a heritable disorder.

Results

All patients underwent microsurgical resection in a multidisciplinary effort by the senior authors. The average tumor size was 4.57 cm, with an average duration of symptoms prior to definitive diagnosis of 31.2 months. The tumor size at the time of presentation followed a trend different from reports in adults, while the duration of symptoms did not. At a follow-up average of 6.3 years (range 1–12 years), 100% of patients demonstrated good facial function (House-Brackmann Grade I or II). No patient in this cohort demonstrated symptoms, objective signs, or genetic analysis indicating the presence of neurofibromatosis Type 2.

Conclusions

Diagnosis and management of sporadic, unilateral VSs in children is complicated by clinical presentations and surgical challenges unique from their adult counterparts. Careful consideration should be given to a heritable genetic basis for sporadic unilateral VS in the pediatric population. Results of genetic testing do not preclude the necessity for long-term follow-up and systemic investigation. In patients who present with large tumors, preliminary experience leads the authors to suggest that a combined retrosigmoid-translabyrinthine approach offers the greatest opportunity for preservation of facial nerve function.