bluuebunny/crossref_metadata_2025 huggingface dataset:
Interface and Electrical Properties of Atomic-layer-deposited HfAlO Gate Dielectric for N-channel GaAs MOSFETs
Authors: Suri Rahul , Lichtenwalner Daniel J , Misra Veena
Published: September 2009

The interface and electrical properties of HfAlO dielectric formed by atomic layer deposition (ALD) on sulfur-passivated GaAs were investigated. X-ray photoelectron spectroscopy (XPS) revealed the absence of arsenic oxides at the HfAlO/GaAs interface after dielectric growth and post-deposition annealing at 500 °C. A minimal increase in the amount of gallium oxides at the interface was detected between the as-deposited and annealed conditions highlighting the effectiveness of HfAlO in suppressing gallium oxide formation. An equivalent oxide thickness (EOT) of ∼ 2 nm has been achieved with a gate leakage current density of less than 10-4 A/cm2. These results testify a good dielectric interface with minimal interfacial oxides and open up potential for further investigation of HfAlO/GaAs gate stack properties to determine its viability for n-channel MOSFETs.
Defects in HfO2 Based Dielectric Gate Stacks
Authors: Lenahan Patrick M. , Ryan Jason T. , Cochrane Corey J. , Conley John F.
Published: September 2009

We report on both conventional electron paramagnetic resonance (EPR) measurements of fully processed HfO2 based dielectric films on silicon and on electrically detected magnetic resonance (EDMR) measurements of fully processed HfO2 based MOSFETs. The magnetic resonance measurements indicate the presence of oxygen vacancy and oxygen interstitial defects within the HfO2 and oxygen deficient silicons in the interfacial layer. The EDMR results also indicate the generation of at least two defects when HfO2 based transistors are subjected to significant negative bias at modest temperature. Our results indicate generation of multiple interface/near interface defects, likely involving coupling with nearby hafnium atoms.
Attempt to Grow α-Rhombohedral Boron Crystals in Copper Solvent
Authors: Gao Wei , Whiteley Clinton , Zhang Yi , Plummer Jack , Edgar James , Gong Yinyan , Kuball Martin
Published: September 2009

An excellent material for thermal neutron detectors is α-rhombohedral boron, due to the large neutron capture cross section of 10B, high hole mobility and ability to self-heal from radiation damage, to date, little work has been done on the crystal growth of α-rhombohedral boron. In this investigation, we attempt to grow α-rhombohedral boron by the solution growth method, employing copper as solvent. Well-faceted transparent red crystals several hundreds of microns in size have been made. Elemental analysis of the crystals detected boron, with negligible amounts of copper, suggesting that copper is a promising solvent for the crystal growth of α-rhombohedral boron crystal.
Effect of oxygen on nanoscale indentation-induced phase transformations in amorphous silicon
Authors: Ruffell Simon , Williams Jim
Published: September 2009

Ion-implantation has been used to introduce oxygen concentration-depth profiles into nominally oxygen-free amorphous silicon (a-Si). The effect of O concentrations in excess of 1018 cm−3 on the formation of high pressure crystalline phases (Si-III and Si-XII) during indentation unloading has been studied. By examination of unloading curves and post-indent Raman micro-spectroscopy O is found to inhibit the so-called pop-out event during unloading and, therefore, the formation of the crystalline phases. Furthermore, at high O concentrations (> 1021 cm−3) the formation of these phases is reduced significantly such that under indentation conditions used here the probability of forming the phases is reduced to almost zero. We suggest that the bonding of O with Si reduces the formation of Si-III/XII during unloading through a similar mechanism to that of oxygen-retarded solid phase crystallization of a-Si.
Artificial neural network model for river flow forecasting in a developing country
Authors: Shamseldin Asaad Y.
Published: September 2009

The present paper deals with exploring the use of Artificial Neural Networks (ANN) for forecasting the Blue Nile river flows in Sudan. Four ANN rainfall–runoff models based on the structure of the well-known multi-layer perceptron are developed. These models use the rainfall index as a common external input, with the rainfall index being a weighted sum of the recent and current rainfall. These models differ in terms of the additional external inputs being used by the model. The additional inputs are basically the seasonal expectations of both the rainfall index and the observed discharge. The results show that the model, which uses both the seasonal expectation of the observed discharge and the rainfall index as additional inputs, has the best performance. The estimated discharges of this model are further updated using a non-linear Auto-Regressive Exogenous-input model (NARXM)-ANN river flow forecasting output-updating procedure. In this way, a real-time river flow forecasting model is developed. The results show that the forecast updating has significantly enhanced the quality of the discharge forecasts. The results also indicate that the ANN has considerable potential to be used for river flow forecasting in developing countries.
Realising social justice in the water sector: 1
Authors: Abbott M. B. , Vojinovic Z.
Published: September 2009

The present work is directed to the analysis, design and construction of web-based systems capable of catalysing processes of stakeholder participation in such ways as to realise changes that are judged by these stakeholders as positive in the water sectors of both the human and the natural economies. The thesis is advanced that the judgement that is so passed is a recognition on the part of the stakeholders of a realisation of social justice. This paper is thus given over in its first part to an analysis of the origins and the nature of social justice in this sector. It is emphasised that, although the resources of hydroinformatics in this endeavour are largely based upon quantitative assessments, the ways in which these translate through stakeholder participation into experiences of social justice are essentially qualitative. Thus, although we are currently concerned for the most part with a hydroinformatics of the quantities, this now has to be extended into a hydroinformatics of the qualities.
Heavy metals in a constructed wetland treating industrial wastewater: distribution in the sediment and rhizome tissue
Authors: Domingos Sergio , Dallas Stewart , Germain Mark , Ho Goen
Published: September 2009

This study assessed copper and zinc distribution in the surface layer of sediment and rhizome tissue within the saturated surface vertical flow constructed wetland of CSBP Ltd, a fertiliser and chemical manufacturer located in Western Australia. Sediment and Schoenoplectus validus rhizome samples were collected at various distances from the inlet pipe while water samples are routinely collected. Water samples were analysed for nutrients and metals, sediments were analysed for total and bioavailable metals and rhizomes were analysed for total metals only. Mean influent copper and zinc concentrations were 0.19 mg/L and 0.24 mg/L respectively. The distribution of bioavailable Cu and Zn in the top sediment layer follows a horizontal profile. Analysis of variance (ANOVA) showed that the bioavailable fraction of these metals in sediments near the inlet pipe (30.2 mg/kg Cu and 60.4 mg/kg Zn) is significantly higher than in sediments at the farthest location (10.3 mg/kg Cu and 26.1 mg/kg Zn). The average total Cu concentration in the sediment at the 2 m location has reached the 65 mg/kg trigger value suggested by the Interim Sediment Quality Guidelines (ANZEEC 2000). Cu and Zn concentrations in the rhizome of S. validus do not vary significantly among different locations. Whether Cu and Zn concentrations at the CSBP wetland may reach toxic levels to plants and bacteria is still unknown and further research is required to address this issue. The surface component of the wetland favours sedimentation and binding of metals to the organic matter on the top of the sediment, furthermore, the sediment which tends to be anoxic with reducing conditions acts as a sink for metals.
Application of particle-size analysis in coagulation/flocculation for reclamation of a secondary effluent
Authors: Liu Hongbo , Sun Liping , Wang Yan , Xia Siqing , Le Linshen
Published: September 2009

Reclaimed secondary effluent is an important alternative water resource for urban areas; the particle-size distribution approach was applied in this study for purpose of screening and evaluating treatment processes for reclamation of a secondary effluent. Two particle-size analysing technologies namely (1) the laser light scattering technology and (2) the sequential membrane filtration technology were used in this study; particulate characteristics of the secondary effluent, of the reclaimed water by coagulation and of the reclaimed water by combined coagulation/flocculation were investigated. Optimisation of coagulation and/or combined coagulation/flocculation technologies were carried out with the help of particulate analysis of priority pollutants, following which studies on turbidity removing mechanisms of both processes were discussed. Comparison studies indicated that increase of turbidity removal efficiency by flocculation happened mainly in the particulate range of 0.2–0.3 μm and 5–8 μm; flocculation did not help or even slightly deteriorated turbidity removal of particles whose sizes are smaller than 0.2 μm and/or in the range of 0.3–5 μm.
Hydrological modeling in alpine catchments: sensing the critical parameters towards an efficient model calibration
Authors: Achleitner S. , Rinderer M. , Kirnbauer R.
Published: September 2009

For the Tyrolean part of the river Inn, a hybrid model for flood forecast has been set up and is currently in its test phase. The system is a hybrid system which comprises of a hydraulic 1D model for the river Inn, and the hydrological models HQsim (Rainfall-runoff-discharge model) and the snow and ice melt model SES for modeling the rainfall runoff form non-glaciated and glaciated tributary catchment respectively. Within this paper the focus is put on the hydrological modeling of the totally 49 connected non-glaciated catchments realized with the software HQsim. In the course of model calibration, the identification of the most sensitive parameters is important aiming at an efficient calibration procedure. The indicators used for explaining the parameter sensitivities were chosen specifically for the purpose of flood forecasting. Finally five model parameters could be identified as being sensitive for model calibration when aiming for a well calibrated model for flood conditions. In addition two parameters were identified which are sensitive in situations where the snow line plays an important role.
Impact of input data uncertainties on urban stormwater model parameters
Authors: Kleidorfer M. , Deletic A. , Fletcher T. D. , Rauch W.
Published: September 2009

The use of urban drainage models requires careful calibration, where model parameters are selected in order to minimize the difference between measured and simulated results. It has been recognized that often more than one set of calibration parameters can achieve similar model accuracy. A probability distribution of model parameters should therefore be constructed to examine the model's sensitivity to its parameters. With increasing complexity of models, it also becomes important to analyze the model parameter sensitivity while taking into account uncertainties in input and calibration data. In this study a Bayesian approach was used to develop a framework for quantification of impacts of uncertainties in the model inputs on the parameters of a simple integrated stormwater model for calculating runoff, total suspended solids and total nitrogen loads. The framework was applied to two catchments in Australia. It was found that only systematic rainfall errors have a significant impact on flow model parameters. The most sensitive flow parameter was the effective impervious area, which can be calibrated to completely compensate for the input data uncertainties. The pollution model parameters were influenced by both systematic and random rainfall errors. Additionally an impact of circumstances (e.g. catchment type, data availability) has been recognized.
A constructed wetland model for synthetic reactive dye wastewater treatment by narrow-leaved cattails (Typha angustifolia Linn.)
Authors: Nilratnisakorn S. , Thiravetyan P. , Nakbanpote W.
Published: September 2009

Textile wastewater is contaminated by reactive dye causing unattractive levels of wastewater color, high pH and high salt content when discharged into public water systems. Decolorization of textile wastewater by plant, phytoremediation, is an alternative, sustainable method which is suitable for long term operation. Narrow-leaved cattails are one species of wetland plant with efficiency for decolorizing and remediating textile wastewater. In addition, chemical oxygen demand (COD) can be lowered and dye residue can be removed. The plant also showed a good salt tolerance even after being exposed to a salt solution for 15 days. The narrow-leaved cattails were set up in a constructed wetland model with a vertical flow system operating from bottom to top for synthetic reactive dye wastewater (SRDW) removal. Narrow-leaved cattails could achieve the removal of SRDW at approximately 0.8 gSRDW m−2 day−1. Decolorization of SRDW by this plant was approximately 60%. The advantage of this method is that it is suitable for textile wastewater management and improvement of wetland. These plants could lower COD, remove dye, sodium and total dissolved solids (TDS) whereas other biological and chemical methods could not remove TDS and dye in the same time. These results suggested that the spongy cell structure of this plant has the ability to absorb large amounts of water and nutrients. Physico-chemical analysis revealed increasing amounts of sulfur, silicon, iron and calcium in the plant leafs and roots after exposure to wastewater. Proteins or amide groups in the plant might help in textile dye removal. Regarding decolorization, this plant accumulates dye in the intercellular space and still grows in this SRDW condition. Hence, it can be noted here that narrow-leaved cattails are efficient for textile dye wastewater treatment.
Transformation of nitrogen and distribution of nitrogen-related bacteria in a polluted urban stream
Authors: Jiao Y. , Jin W. B. , Zhao Q. L. , Zhang G. D. , Yan Y. , Wan J.
Published: September 2009

Most researchers focused on either nitrogen species or microbial community for polluted urban stream while ignoring the interaction between them and its effect on nitrogen transformation, which restricted the rational selection of an effective and feasible remediation technology. Taking Buji stream in Shenzhen (China) as target stream, the distribution of nitrogen-related bacteria was investigated by most probable number (MPN) besides analysis of nitrogen species etc. The nitrogen-related bacteria in sediment were 102 times richer than those in water. Owing to their faster growth, the MPN of ammonifying bacteria and denitrifying bacteria were 105 and 102 times higher than those of nitrifying bacteria, respectively. The ammonifying bacteria numbers were significantly related to BOD5 in water, while nitrifying bacteria in sediment correlated well with nitrate in water. Thus, nitrification occurred mainly in sediment surface and was limited by low proportion of nitrifying bacteria. The denitrifying bacteria in sediment had good relationship with BOD5 and nitrite and nitrate in water. Low DO and rich organic compounds were beneficial to denitrification but unfavourable to nitrification. Denitrification was restricted by low nitrite and nitrate concentration. These results could be served as a reference for implementing the remediation scheme of nitrogen polluted urban stream.
Importance of Particulate Biodegradable Organic Compounds in Performance of Full‐scale Biological Phosphorus Removal System
Authors: Tunçal Tolga , Pala Ayşegül , Uslu Orhan
Published: September 2009

In this study, biological treatment performances of two parallel treatment lines operating with and without primary sedimentation were investigated. The research was carried out in a large‐scale enhanced biological phosphorus removal (EBPR) process. Influent and effluent of treatment lines were characterized continuously during the study. In addition, anaerobic anoxic and aerobic EBPR activities were investigated by batch tests using fresh activated sludge samples. All of the environmental and operational conditions of the treatment lines were statistically compared. Evaluation of effluent compositions indicated that EBPR performances of treatment lines were significantly different. Results of the research also indicated that settling characteristics of the activated sludge process could be improved significantly with increasing particulate biodegradable organic compound (pbCOD) loading rate. Batch test results revealed that anaerobic, anoxic, and aerobic biochemical reaction rates of activated sludge cultivated on increased pbCOD loading rate were significantly higher compared to activated sludge cultivated on soluble substrate forms.
Kinetics and Thermodynamics of Arsenate and Arsenite Biosorption by Pretreated Spent Grains
Authors: Chai Liyuan , Chen Yunnen , Yang Zhihui
Published: September 2009

Using chemically modified spent grains as a new biosorbent to treat arsenate and arsenite ions was studied. The influences of pH, contact time, initial concentration and temperature were studied in batch experiments. The equilibrium process was described well by Langmuir isotherm model with maximum biosorption capacities of 13.39 and 4.86 mg/g of arsenate and arsenite on spent grains, respectively. The initial removal was rapid, and equilibrium was established in less than 180 min. Good correlation coefficients were obtained for the pseudo‐second‐order kinetic model. In the binary metal solutions, the finite sites on the surface of spent grains showed a greater preference for As(V) ions. The enthalpy of biosorption was exothermic and the increase in As(III) removal was larger than that of As(V) over the same rise in temperature. In this study, spent grains proved to be suitable for removal of As(V) and As(III) from the effluent of metallurgical industry.
On the MPC of the Methanol Synthesis in a Simulated Moving Bed
Authors: Fissore Davide
Published: September 2009

This paper is focused on the design of a Model Predictive Control (MPC) algorithm to control and optimize the methanol synthesis in a Simulated Moving Bed (SMB) reactor. First, the advantages that can be obtained when the process in carried out in this reactor configuration are summarized; then, the control algorithm is described. A simplified model based on Artificial Neural Networks (ANN) is used to calculate the control actions. The influence of the tuning parameters of the algorithm is studied by means of mathematical simulation, thus resulting in the best controller configuration. Finally, examples of the performance of the controlled system are provided, thus demonstrating the effectiveness of the proposed tool.
In utero meconium passage in fetuses and newborns with myelomeningocele
Authors: Danzer Enrico , Ernst Linda M. , Rintoul Natalie E. , Johnson Mark P. , Adzick N. Scott , Flake Alan W.
Published: September 2009

Object

The authors retrospectively investigated whether midgestational fetal myelomeningocele (fMMC) repair alters intrauterine meconium exposure.

Methods

Prior to the National Institutes of Health Management of Myelomeningocele Study, 54 fetuses underwent fMMC repair at the authors' institution. Forty-six fMMC sacs were available for pathological examination and 53 MMC sacs from postnatally repaired MMCs (pMMCs) were available for comparison. The presence and distribution of meconium were blindly evaluated using a grading system defined as follows: absent (no meconium present), mild (< 10 meconium-positive histiocytes [MPHs]/hpf), moderate (10–25 MPHs/hpf), and severe (> 25 MPHs/hpf). Hall's bile stain was used to confirm meconium and Prussian blue and Fontana Masson stains to exclude hemosiderin and melanin, respectively.

Results

Compared to pMMCs (79%), meconium histiocytosis was less prevalent in fMMC sacs (57%; p = 0.017). Meconium staining was completely absent in 43% of the fMMC sacs. Mild meconium histiocytosis was found in 35% fMMC and 61% pMMC sacs (p = 0.035). There was no statistical difference between groups with moderate and severe meconium histiocytosis.

Conclusions

Meconium passage in MMCs can occur early in fetal life. Fetal MMC repair may reduce the duration of meconium exposure, thereby potentially limiting the toxic injury to the vulnerable neural elements.
Endovascular transvenous embolization of sinus pericranii
Authors: Brook Allan L. , Gold Menachem M. , Farinhas Joaquim M. , Goodrich James T. , Bello Jacqueline A.
Published: September 2009

Sinus pericranii (SP) is an abnormal communication between the intra- and extracranial venous drainage pathways. Treatment of this condition has mainly been recommended for reasons of cosmesis and prevention of hemorrhage. The authors report a novel endovascular transvenous route for definitive treatment of SP.
Open reduction and internal fixation of a lumbar Chance fracture in a child using Songer cable and lamina plates
Authors: Baaj Ali A. , Uribe Juan S. , Vale Fernando L.
Published: September 2009

Chance-type fractures of the spine have been associated with seat-belt injuries in the pediatric population. Nonoperative management is appropriate in most cases of Chance fractures, but surgical intervention is occasionally warranted to deter progression of kyphosis and neurological deterioration. Internal fixation using pedicle screws has been widely used in the surgical repair of this injury. The authors report on a 6-year-old girl who suffered an L-2 Chance fracture with facet disruption, kyphosis, and significant posterior ligamentous injury. She underwent open reduction and internal fixation using Songer cable wiring augmented with bilateral lamina plating. At the 18-week follow-up, she continued to be free of any neurological deficits and her alignment was stable on plain radiographs of flexion-extension. The authors have therefore described a feasible option in the surgical management of Chance-type fractures in the pediatric spine.
Computed tomography morphometric analysis for axial and subaxial translaminar screw placement in the pediatric cervical spine
Authors: Chern Joshua J. , Chamoun Roukoz B. , Whitehead William E. , Curry Daniel J. , Luerssen Thomas G. , Jea Andrew
Published: September 2009

Object

The management of upper cervical spinal instability in children continues to represent a technical challenge. Traditionally, a number of wiring techniques followed by halo orthosis have been applied; however, they have been associated with a high rate of nonunion and poor tolerance for the halo. Alternatively, C1–2 transarticular screws and C-2 pars/pedicle screws allow more rigid fixation, but their placement is technically demanding and associated with vertebral artery injuries. Recently, C-2 translaminar screws have been added to the armamentarium of the pediatric spine surgeon as a technically simple and biomechanically efficient means of fixation. However, the use of subaxial translaminar screws have not been described in the general pediatric population. There are no published data that describe the anatomical considerations and potential limitations of this technique in the pediatric population.

Methods

The cervical vertebrae of 69 pediatric patients were studied on CT scans. Laminar height and thickness were measured. Statistical analysis was performed using unpaired Student t-tests (p < 0.05) and linear regression analysis.

Results

The mean laminar heights at C-2, C-3, C-4, C-5, C-6, and C-7, respectively, were 9.76 ± 2.22 mm, 8.22 ± 2.24 mm, 8.09 ± 2.38 mm, 8.51 ± 2.34 mm, 9.30 ± 2.54 mm, and 11.65 ± 2.65 mm. Mean laminar thickness at C-2, C-3, C-4, C-5, C-6, and C-7, respectively, were 5.07 ± 1.07 mm, 2.67 ± 0.79 mm, 2.18 ± 0.73 mm, 2.04 ± 0.60 mm, 2.52 ± 0.66 mm, and 3.84 ± 0.96 mm. In 50.7% of C-2 laminae, the anatomy could accept at least 1 translaminar screw (laminar thickness ≥ 4 mm).

Conclusions

Overall, the anatomy in 30.4% of patients younger than 16 years old could accept bilateral C-2 translaminar screws. However, the anatomy of the subaxial cervical spine only rarely could accept translaminar screws. This study establishes anatomical guidelines to allow for accurate and safe screw selection and insertion. Preoperative planning with thin-cut CT and sagittal reconstruction is essential for safe screw placement using this technique.
Developmental outcomes for neonatal dural arteriovenous fistulas
Authors: Johnson Jonathan N. , Hartman Tyler K. , Barbaresi William , Raffel Corey , Colby Christopher E.
Published: September 2009

Large dural arteriovenous malformations (DAVMs) accompanied by cardiac failure usually carry a poor prognosis with a high risk of morbidity and death. The authors report on the case of a male neonate with a massive DAVM who presented at birth with macrocephaly and high-output cardiac failure. The child initially underwent treatment with surgical clipping of the large main feeding artery. Hydrocephalus, thought to be due to venous hypertension, developed when the boy was 8 months old. The condition resolved after interventional embolization treatment. The patient did not require placement of a ventriculoperitoneal shunt. At 21 months of age, the child had near normal development without any focal neurological deficits.
Reversal of sedation with flumazenil in a child after traumatic brain injury
Authors: Ochalski Pawel G. , Okonkwo David O. , Bell Michael J. , Adelson P. David
Published: September 2009

The authors report on a case of successful reversal of sedation with flumazenil, a benzodiazepine antagonist, in a child following a moderate traumatic brain injury and demonstrate the utility of flumazenil to reverse benzodiazepine effects in traumatically injured children.
Indolent dorsal midbrain tumor: new findings based on positron emission tomography
Authors: Yamaguchi Shigeru , Terasaka Shunsuke , Kobayashi Hiroyuki , Shiga Tohru , Usui Reiko , Hirata Kenji , Kubota Kanako , Murata Junichi , Iwasaki Yoshinobu
Published: September 2009

Object

Intrinsic tumors arising in the dorsal midbrain cause obstructive hydrocephalus and have an indolent clinical course. Positron emission tomography (PET) with fluorine-18–labeled fluorodeoxyglucose (FDG) and l- [methyl-11C]methionine (MET) was used to evaluate the biological behaviors of dorsal midbrain tumors.

Methods

The authors report on 4 patients (3 males and 1 female) with dorsal midbrain tumors who presented with obstructive hydrocephalus. A diagnosis was made with MR imaging in each patient. To manage the hydrocephalus, endoscopic third ventriculostomy was performed in all cases. The patients did not undergo any other surgical procedures except endoscopic biopsy procedure, chemotherapy, or radiation therapy. The patients in 3 cases underwent FDG- and MET-PET within 6 months of CSF-diverting procedures, and the patient in 1 case underwent PET 10 years after the procedure.

Results

After the CSF-diverting procedure, clinical symptoms resolved or improved in all patients. Gliosis or glial proliferation was diagnosed in 1 patient, and possible low-grade glioma in 2 patients. Although all tumors appeared hyperintense on T2-weighted MR images, their appearance on T1-weighted images was variable (iso- and/or hypointense), and partial lesion enhancement was observed on images from 2 patients. On the other hand, the PET features of these lesions were almost identical, and the scans did not show a high uptake of FDG and MET compared with the cortical uptake in a normal brain. The mean tumor tissue/normal tissue ratio of FDG uptake was 0.65, and that of MET was 0.99.

Conclusions

Positron emission tomography findings suggested that the indolent dorsal midbrain lesion had nontumorous characteristics, thus supporting a good prognosis. Positron emission tomography studies may be more informative and predictive of the biological behavior of dorsal midbrain tumors than a biopsy procedure.
Onyx embolization of a thoracolumbar perimedullary spinal arteriovenous fistula in an infant presenting with subarachnoid and intraventricular hemorrhage
Authors: Kenning Tyler J. , Deshaies Eric M. , Adamo Matthew A. , Waldman John B. , Boulos Alan S.
Published: September 2009

Identifying a source of spontaneous subarachnoid hemorrhage (SAH) or intraventricular hemorrhage (IVH) in patients with negative results on cranial angiographic imaging can be a diagnostic challenge. The authors present the case of a 14-month-old girl who presented with lethargy and spontaneous SAH and IVH, and later became acutely paraplegic. Except for the SAH and IVH, findings on neuroimages of the brain were normal. Magnetic resonance imaging revealed an intramedullary thoracolumbar spinal cord hemorrhage that was found to be associated with arterialized veins intraoperatively. Catheter-based diagnostic angiography identified a spinal perimedullary macroarteriovenous fistula (macro-AVF) that was completely embolized with Onyx, negating the need for further surgical intervention. The authors believe this to be the first reported case of a thoracolumbar perimedullary macro-AVF presenting with SAH and IVH. In addition, descriptions of Onyx embolization of a spinal AVF in the literature are rare, especially in pediatric patients.
Ectopic glioneuronal tissue in the middle cranial fossa region
Authors: Abel Taylor J. , Chowdhary Abhineet , Thapa Mahesh , Rutledge Joseph C. , Gruss Joseph , Manning Scott , Avellino Anthony M.
Published: September 2009

The growth of ectopic glioneuronal tissue in the middle cranial fossa region is an uncommon event, with very few cases reported in the literature. In this paper the authors document 4 cases of ectopic glioneuronal tissue in the middle cranial fossa in children and briefly describe the clinical course and pathology. All of the children presented within the first 6 months of life. Two children presented with facial masses, 1 with airway obstruction, and another with proptosis of the right eye. Each child underwent a customized surgery dependent on the location and characteristics of the harbored lesion. Ectopic glioneuronal masses in the middle cranial fossa are rare and benign congenital tumors, and affected newborns can present with airway obstruction, feeding difficulties, and facial deformity depending on the lesion location. Determining an appropriate surgical approach and strategy is a significant challenge and may involve a multidisciplinary team of craniofacial plastic surgeons, otolaryngologists, and neurosurgeons. Although these lesions share clinical and anatomical similarities, because of their histopathological heterogeneity, it is unlikely that they represent a single pathological entity. The long-term outcome in these children is still unknown and is an area for future study. The pathogenesis of these lesions also remains unknown and may be revealed in future research.
Spinal congenital dermal sinus with dual ostia
Authors: Lee Chang Sub , Phi Ji Hoon , Kim Seung-Ki , Cho Byung-Kyu , Wang Kyu-Chang
Published: September 2009

Object

Congenital dermal sinus (CDS) usually develops in the midline of the body as a single tract. To date, only a few patients with multiple CDS tracts and ostia have been reported. The authors analyzed the clinical features of patients with spinal CDS and multiple ostia and proposed a novel hypothesis for the pathogenesis of the atypical CDS.

Methods

Five patients with spinal CDS and multiple ostia were included. The clinical, radiological, and operative features of these patients were reviewed retrospectively.

Results

Three patients demonstrated bilateral paramedian ostia at the same or a very similar spinal level. One patient showed a paramedian and a midline ostium. One patient had 2 unilateral paramedian ostia at different spinal levels. The layers of the internal ending of CDS tracts were diverse. Complete removal of the tracts was possible in all patients. Two patients had dermoid tumors. All patients had an associated anomaly, such as a lumbosacral lipoma or the Currarino triad. The authors propose a “zipping error” hypothesis for the formation of dual ostia located at the spinal level of primary neurulation. An associated anomaly such as a lumbosacral lipoma may contribute to the formation of dual ostia.

Conclusions

Unilateral or bilateral dual ostia may be present in patients with CDS, especially when an associated anomaly is present. The atypical CDS may develop from aberrant neural tube closure.
A model for neurosurgical humanitarian aid based on 12 years of medical trips to South and Central America
Authors: Mainthia Rajshri , Tye Gary W. , Shapiro Jay , Doppenberg Egon M. R. , Ward John D.
Published: September 2009

The pediatric neurosurgical mission trips led by physicians at Virginia Commonwealth University (VCU) Health Systems began in 1996 with the formation of Medical Outreach to Children, founded by 1 of the authors (J.D.W.) after a visit to Guatemala. Since then, 19 surgical trips to 4 different countries in Central and South America have been coordinated from 1996 to 2008.

This humanitarian work serves a number of purposes. First and foremost, it provides children with access to surgical care that they would otherwise not receive, thereby significantly improving their quality of life. Second, the visiting surgical team participates in the education of local physicians, parents, and caregivers to help improve the healthcare provided to the children. Last, the team works to promote sustainable global health solutions in the countries it travels to by generating a forum for clinical and public health research discourse.

Thus far, a total of 414 children have undergone 463 operations, including 154 initial shunt surgeries, 110 myelomeningocele repairs, 39 lipoma resections, 33 tethered cord releases, 18 shunt revisions, 16 encephalocele repairs, 9 lipomyelomeningocele repairs, and 7 diastematomyelia repairs. The complication rate has been 5–8%, and the team has obtained reliable follow-up in ~ 77% of patients. A correlation was found between an increase in the number of trained neurosurgeons in the host countries and a decrease in the average age of patients treated by the visiting surgical team over time. It is also hypothesized that a decrease in the percentage of myelomeningocele repairs performed by the surgical team (as a fraction of total cases between 1996 and 2006) correlates to an increase in the number of local neurosurgeons able to treat common neural tube defects in patients of younger ages. Such analysis can be used by visiting surgical teams to assess the changing healthcare needs in a particular host country.
Surgical outcome of tuberculous meningitis hydrocephalus treated by endoscopic third ventriculostomy: prognostic factors and postoperative neuroimaging for functional assessment of ventriculostomy
Authors: Chugh Ashish , Husain Mazhar , Gupta Rakesh K. , Ojha Bal K. , Chandra Anil , Rastogi Manu
Published: September 2009

Object

Endoscopic third ventriculostomy (ETV) is increasingly being used as an alternative treatment for post–tuberculous meningitis (TBM) hydrocephalus. The aim of this study was to affirm the role of ETV in patients with TBM hydrocephalus and also to study the usefulness of cine phase-contrast MR imaging (cine MR imaging) for functional assessment of the ETV stoma. An additional goal was to identify factors that influence the outcome of ETV, so as to define patients with TBM hydrocephalus in whom ETV is warranted.

Methods

Twenty-six patients with TBM hydrocephalus treated with ETV were evaluated clinically and with cine MR imaging postoperatively. The duration of follow-up ranged from 1 to 15 months. The authors evaluated flow void changes in the floor of the third ventricle and analyzed parameters from the preoperative data, which they then used as a basis for comparison between endoscopically successful and endoscopically unsuccessful cases.

Results

The overall success rate of ETV in TBM hydrocephalus was 73.1% in this case series. Cine MR imaging showed a sensitivity of 94.73% and specificity of 71.42% for the functional assessment of third ventriculostomy in these patients, with the efficacy being maintained during follow-up. The outcome of ETV showed a statistically significant correlation with the stage of illness and presence of intraoperative cisternal exudates. Although duration of symptoms and duration of preoperative antituberculous therapy (ATT) appeared to influence the outcome, their correlation with outcome was not statistically significant.

Conclusions

Endoscopic third ventriculostomy should be considered as the first surgical option for CSF diversion (that is, before shunt surgery) in patients with TBM hydrocephalus. Cine MR imaging is a highly effective noninvasive tool for the postoperative functional assessment of stomata. Patients who presented with a history of longer duration and those who were administered preoperative ATT for a longer period had a better outcome of endoscopic treatment. Outcome was poorer in patients who presented with higher stages of illness and in those in whom cisternal exudates were observed intraoperatively.
Management of cervical spine injuries in young children: lessons learned
Authors: Smith Jodi L. , Ackerman Laurie L.
Published: September 2009

Previous studies have shown that the correct use of car safety seats can protect infants and children from vehicular injury. Although child passenger devices are increasingly used in the US, motor vehicle crashes continue to be the leading cause of death and acquired disability in infants and children younger than 14 years of age. These events are likely related, at least in part, to the high percentage of children who are unrestrained or improperly restrained. The authors present 2 cases of severe cervical spine trauma in young children restrained in car safety seats during a motor vehicle crash: 1) a previously healthy 14-month-old girl who was improperly restrained in a forward-facing booster seat secured to the vehicle by a lap belt, and 2) a previously healthy 30-month-old girl who was a rear seat passenger restrained in a car safety seat. This study points out the unique challenges encountered in treating cervical spine injuries in infants and young children, as well as the lessons learned, and emphasizes the significance of continuing efforts to increase family and public awareness regarding the importance of appropriate child safety seat selection and use.
A multicenter retrospective comparison of conversion from temporary to permanent cerebrospinal fluid diversion in very low birth weight infants with posthemorrhagic hydrocephalus
Authors: Wellons John C. , Shannon Chevis N. , Kulkarni Abhaya V. , Simon Tamara D. , Riva-Cambrin Jay , Whitehead William E. , Oakes W. Jerry , Drake James M. , Luerssen Thomas G. , Walker Marion L. , Kestle John R. W. , _ _
Published: September 2009

Object

The purpose of this study was to define the incidence of permanent shunt placement and infection in patients who have undergone the 2 most commonly performed temporizing procedures for posthemorrhagic hydrocephalus (PHH) of prematurity: ventriculosubgaleal (VSG) shunt placement and ventricular reservoir placement for intermittent tapping.

Methods

The 4 centers of the Hydrocephalus Clinical Research Network participated in a retrospective chart review of infants with PHH who underwent treatment at each institution between 2001 and 2006. Patients were included if they had received a diagnosis of Grade 3 or 4 intraventricular hemorrhage, weighed < 1500 g at birth, and had received surgical intervention. The authors determined the incidence of conversion from a temporizing device to a permanent shunt, the incidence of CSF infection during temporization, and the 6-month CSF infection rate after permanent shunt placement.

Results

Thirty-one (86%) of 36 patients who received VSG shunts and 61 (69%) of 88 patients who received ventricular reservoirs received permanent CSF diversion with a shunt (p = 0.05). Five patients (14%) in the VSG shunt group had CSF infections during temporization, compared with 11 patients (13%) in the ventricular reservoir group (p = 0.83). The 6-month incidence of permanent shunt infection in the VSG shunt group was 16% (5 of 31), compared with 12% (7 of 61) in the reservoir placement group (p = 0.65). For the first 6 months after permanent shunt placement, infants with no preceding temporizing procedure had an infection rate of 5% (1 of 20 infants) and those who had undergone a temporizing procedure had an infection rate of 13% (12 of 92; p = 0.45).

Conclusions

The use of intermittent tapping of ventricular reservoirs in this population appears to lead to a lower incidence of permanent shunt placement than the use of VSG shunts. The incidence of infection during temporization and for the initial 6 months after conversion appears comparable for both groups. The apparent difference identified in this pilot study requires confirmation in a more rigorous study.
Enlarged thalamostriate vein causing unilateral Monro foramen obstruction
Authors: Leonardo Jody , Grand Walter
Published: September 2009

Causes of unilateral hydrocephalus resulting from an obstruction at the Monro foramen include foraminal atresia, tumors, gliosis, contralateral shunting, and infectious and inflammatory conditions. However, few reports in the literature cite vascular lesions as the cause of the obstruction. To their knowledge, the authors present the first report of unilateral hydrocephalus occurring due to an abnormally enlarged thalamostriate vein independent of an arteriovenous malformation or developmental venous angioma. The condition was treated successfully by endoscopic septum pellucidum fenestration. A 28-year-old man was referred for evaluation due to a 10-year history of chronic headaches that worsened in severity over the past year. A CT scan of the head revealed unilateral right ventricular dilation. Cranial MR imaging with and without contrast administration showed a dilated right thalamostriate–internal vein complex without any evidence of associated arteriovenous malformation or venous angioma. Endoscopic exploration of the right lateral ventricle showed an enlarged subependymal thalamostriate vein obstructing the Monro foramen. An endoscopic fenestration of the septum pellucidum was performed, resulting in alleviation of the patient's symptoms. Abnormally enlarged venous structures may cause obstructive unilateral hydrocephalus and can be a rare cause of chronic, intermittent headaches in adults. Endoscopic fenestration of the septum pellucidum is an effective treatment.
A new fiber-mediated carbon dioxide laser facilitates pediatric spinal cord detethering
Authors: Browd Samuel R. , Zauberman Jacob , Karandikar Mahesh , Ojemann Jeffery G. , Avellino Anthony M. , Ellenbogen Richard G.
Published: September 2009

Object

The authors report their experience with a novel flexible fiber capable of transmitting CO2 laser energy during spinal cord tumor resection and detethering.

Methods

A fiber optic system capable of transmitting CO2 laser energy was used in the detethering of the spinal cord in 3 cases. The first case involved a 9-year-old girl with a terminal lipoma. The second case was an 11-month-old boy with a thoracic intramedullary dermoid and dermal sinus tract. The third case involved a 13-year-old girl suffering from a tethered spinal cord subsequent to a previously repaired myelomeningocele.

Results

In all 3 cases, the new fiber CO2 laser technology allowed the surgeon to perform microsurgical dissection while sparing adjacent neurovascular structures without time-consuming setup. The system was easy to implement, more ergonomic than previous technologies, and safe. The CO2 laser provided the ability to cut and coagulate while sparing adjacent tissue because of minimal energy dispersion and ease of use, without the articulating arms involved in the prior generation of lasers.

Conclusions

Using a flexible fiber to conduct CO2 laser energy allows accurate microneurosurgical dissection and renders this instrument a high-precision and ergonomic surgical tool in the setting of spinal cord detethering.
Survival and functional outcome of childhood spinal cord low-grade gliomas
Authors: Scheinemann Katrin , Bartels Ute , Huang Annie , Hawkins Cynthia , Kulkarni Abhaya V. , Bouffet Eric , Tabori Uri
Published: September 2009

Object

Intramedullary spinal cord low-grade gliomas (LGGs) are rare CNS neoplasms in pediatric patients, and there is little information on therapy for and outcome of these tumors in this population. Furthermore, most patient series combine adult and pediatric patients or high- and low-grade tumors, resulting in controversial data regarding optimal treatment of these children. To clarify these issues, the authors performed a regional population-based study of spinal cord LGGs in pediatric patients.

Methods

All pediatric patients with LGGs treated during the MR imaging era (1985–2007) were identified in the comprehensive database of the Hospital for Sick Children in Toronto. Data on demographics, pathology, treatment details, and outcomes were collected.

Results

Spinal cord LGGs in pediatric patients constituted 29 (4.6%) of 635 LGGs. Epidemiological and clinical data in this cohort were different than in patients with other spinal tumors and strikingly similar to data from pediatric patients with intracranial LGGs. The authors observed an age peak at 2 years and a male predominance in patients with these tumors. Histological testing revealed a Grade I astrocytoma in 86% of tumors. Although 5-year progression-free survival for the entire group was 48 ± 9%, all patients were alive at a median follow-up of 8.2 years. Five-year progression-free survival was 88 ± 13% for patients undergoing gross-total resection and 34 ± 11% for those undergoing all other therapies, respectively (p = 0.02). Chemotherapy and radiation therapy showed similar efficacy, achieving sustained tumor control in most patients. However, this excellent survival rate was associated with an 83% rate of significant neurological and orthopedic sequelae.

Conclusions

This study provides basic data on the incidence, clinical course, and outcome of spinal cord LGGs in pediatric patients. The similarities between spinal and intracranial LGGs in pediatric patients showing excellent survival but high morbidity suggest that a less aggressive approach may be the preferable treatment option for these patients.