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Search Results: 1 - 10 of 12099 matches for " Stephen Pirris "
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Endovascular Treatment and Selective Image Guided Partial Resection of Epidural Spinal Vascular Malformation in Klippel-Trenaunay Syndrome: Case Report  [PDF]
Ramon Navarro, Stephen Pirris, Ricardo A. Hanel
Open Journal of Modern Neurosurgery (OJMN) , 2014, DOI: 10.4236/ojmn.2014.44035
Abstract: Background: Klippel-Trenaunay-Weber syndrome is a rare congenital condition that may involve the central nervous system with extensive vascular malformations, and soft-tissue hypertrophy of the affected limb. Methods: A 51-year-old patient underwent previous procedures including decompressive laminectomy and endovascular embolization using Onyx and a self-expandable stent. However, recanalization of the malformation was observed, his symptoms progressed, and the decision was made to undergo selective surgical resection with intraoperative image guidance using Stealth system paired with the O-arm. Results: Adequate decompression of the affected spinal cord and cervical roots were obtained, and the patient’s symptoms improved. Conclusion: Since the typical anatomic landmarks were obliterated by the extensive vascular malformation and previous surgery, intraoperative image guidance proved to be very beneficial. This case reports on the usage of spinal navigation to efficiently dissect out the affected nerve roots and avoid vascular injury by referencing the Onyx and stent.
Synovial Cyst Mimicking an Intraspinal Sacral Mass
Jason Hoover,Stephen Pirris
Case Reports in Neurological Medicine , 2014, DOI: 10.1155/2014/953579
Abstract: A 68-year-old female had a three-week history of severe low back pain radiating down the posterior left buttocks and left leg exacerbated by standing and walking. Lumbar spine MRI revealed cystic mass with similar intensity to cerebrospinal fluid located on dorsolateral left side of the sacral spinal canal inferior to the S1 pedicle. There was compression of left exiting S1 and traversing S2 nerve roots. Neurosurgery consult was requested to evaluate the cystic mass in the sacral spinal canal. After clinical evaluation, an unusually located synovial cyst was thought possible. Cyst contents were heterogeneous, suggestive of small hemorrhage and acute clinical history seemed reasonable. Left S1 and partial left S2 hemilaminectomy was performed and an epidural, partially hemorrhagic cyst was removed. There was no obvious connection to the ipsilateral L5-S1 facet joint. Pathology revealed synovial cyst, and the patient’s leg pain was improved postoperatively. This synovial cyst was unusual as it had no connection with the facet joint intraoperatively and its location in the sacral canal was uncommon. 1. Case Presentation 1.1. Presentation and History A 68-year-old female with a long history of intermittent back pain had a relatively acute onset of severe low back pain radiating down the posterior left buttocks and left leg for three weeks. She denied any trauma or other possible inciting factors. The pain had been getting progressively worse, and she also had developed numbness in the left S1 and S2 dermatomal distributions. An epidural steroid injection performed at a local facility provided partial relief and lasted for approximately 24 hours. The pain was described as intense, electrical pain different from any pain she had ever felt in terms of distribution and severity. Due to the exacerbating factors including standing and walking, thus, she presented to clinic in a wheelchair and preferred to lay in the fetal position. She had presented to the emergency department two days prior to neurosurgery consultation due to continued worsening of pain and numbness. 1.2. Physical Examination A thorough neurological examination was negative except for a positive straight leg raise on the left. 1.3. Initial Diagnosis and Radiography Lumbar spine X-ray did not reveal any abnormal alignment or transitional anatomy (Figure 1). Lumbar spine MRI (Figures 2 and 3) revealed a cystic mass with similar intensity to cerebrospinal fluid (T2 hyperintense/T1 hypointense) located on the dorsolateral left side of the sacral spinal canal inferior to the left S1 pedicle. It was
Symptomatic Pneumocephalus Associated with Lumbar Dural Tear and Reverse Trendelenburg Positioning: A Case Report and Review of the Literature
Stephen M. Pirris,Eric W. Nottmeier
Case Reports in Neurological Medicine , 2013, DOI: 10.1155/2013/792168
Abstract: Symptomatic pneumocephalus is a rare complication of degenerative lumbar spine surgery. This is a case report of a patient who developed transient diplopia associated with pneumocephalus following lumbar spine surgery complicated by a dural tear. The diplopia improved as the pneumocephalus resolved. Factors involved in the development of pneumocephalus include an unintended durotomy and intraoperative reverse Trendelenburg positioning that was utilized to decrease the risk of postoperative vision loss. When encountering cerebrospinal fluid (CSF) leakage intraoperatively, spine surgeons should level the operating table until closure of the dural defect to prevent potential complications associated with pneumocephalus. If postoperative patients complain of severe headaches or display a focal cranial neurologic deficit, then a computed tomography (CT) scan of the brain should be ordered and evaluated. Consulting neurologists should be aware of the circumstances surrounding this rare complication. 1. Introduction Symptomatic pneumocephalus is a rare complication of degenerative lumbar spine surgery. This is a case report of a patient who developed transient diplopia associated with pneumocephalus following lumbar spine surgery, which then improved as the pneumocephalus resolved. Factors involved in the development of pneumocephalus included an unintended durotomy and reverse Trendelenburg positioning that was utilized to decrease the risk of postoperative vision loss. As spine surgeons increasingly position patients in this fashion, the risk of pneumocephalus associated with dural tears will correspondingly increase. Therefore, the recommendation is to level the operating table when a dural tear is encountered and to raise the head of bed only after satisfactorily closing the dural defect. Consulting neurologists for patients in the postoperative period may benefit from being aware of intraoperative reverse Trendelenburg positioning possibly contributing to the risk of pneumocephalus. 2. Case Presentation A 65-year-old male presented with a surgical history of an L2–4 posterior instrumented arthrodesis performed at a local hospital. Previous history included a vitreous humor hemorrhage in the left eye, resulting in slightly decreased vision in that eye. The patient is a former professional golfer. He was able to return to playing golf approximately six months after his previous surgery. Over the past year, he had a significant decline in his ability to ambulate due to recurrent low back pain radiating down both lower extremities, which was consistent with
Resilience: The New Paradigm in Disaster Management—An Australian Perspective  [PDF]
Stephen Jenkins, Stephen Jenkins
World Journal of Engineering and Technology (WJET) , 2015, DOI: 10.4236/wjet.2015.33C020

During past decades, frameworks relating to emergency and disaster management have been based on a risk management approach to prevention/mitigation and preparedness coupled with a strong emphasis on response by police and emergency service organisations. Numerous reviews and inquiries of significant events however have identified significant issues relating to the preparation for such events and the management thereof; in particular, critical shortcomings in the capability of emergency response agencies, their leaders and senior decision-makers. In 2008, the Australian Government, through The First National Security Statement to the Australian Parliament by Prime Minister Rudd, has incorporated non-traditional threats and hazards, such as those posed by the impact of climate change, on the national security agenda. In doing so, the Government has announced a paradigm shift in policy for the nation’s approach to emergency and disaster management, namely a move from “response” to “resilience”. In support of this policy shift, the Australian Government, through the Council of Australian Governments, has endorsed the National Strategy for Disaster Resilience and the Critical Infrastructure Resilience Strategy. These documents make resilience the responsibility of all levels of government, private industry, emergency response agencies, and the community. A review of the reports published following Australian reviews and inquiries into significant events has identified that existing frameworks do not provide the necessary mechanisms for baselining and assessing community resilience, that is, their ability to respond to and recover from significant events. Internationally, indices have been developed for assessing community resilience, however, inherent limitations have also been identified in their scope and application. This paper will review Australian and international events which have led to inquiries that have resulted in criticisms of the emergency and disaster response, as well as introducing the organisational capability and resilience of organisations particularly in the context of climate change.

Assessing Bias: The Qualitative in the Quantitative, Darfuri War Fatalities and the Morality of War  [PDF]
Stephen Reyna
Sociology Mind (SM) , 2011, DOI: 10.4236/sm.2011.13013
Abstract: This paper formulates a strategy for assessing bias, and applies it to quantitative assessments of the disaster of war in Darfur [Sudan]. In so doing it argues for qualitative investigations of quantitative analyses. The strategy examines epistemic and political regimes with the goal of revealing the sources, the directions, and the forces of bias. Examples of bias are discussed to illustrate the strategy including, among others, the draw-a-person IQ test, questions about how old you are or whether you can bear children in Chad, and the US army’s Human Terrain System. Considerable attention is paid to US governmental biasing of its claims of war fatalities and genocide in Darfur. This biasing is shown to involve cherry picking, symbolic violence, and high-channel regimes of bias. It is shown how the bias assessment strategy may be of use in evaluating moral claims.
Organs-on-a-Chip: A Future of Rational Drug-Design  [PDF]
Stephen Shay
Journal of Biosciences and Medicines (JBM) , 2017, DOI: 10.4236/jbm.2017.59003
Abstract: Many recent advances in biomedical research are related to the combination of biology and microengineering. Microfluidic devices, such as organ-on-a-chip systems, integrate with living cells to allow for the detailed in vitro study of human physiology and pathophysiology. With the poor translation from animal models to human models, the organ-on-a-chip technology has become a promising substitute for animal testing, and their small scale enables precise control of culture conditions and high-throughput experiments, which would not be an economically sound model on a macroscopic level. These devices are becoming more and more common in research centers, clinics, and hospitals, and are contributing to more accurate studies and therapies, making them a staple technology for future drug design.
Compromise in CDMA Network Planning  [PDF]
Stephen Hurley, Leigh Hodge
Communications and Network (CN) , 2010, DOI: 10.4236/cn.2010.23023
Abstract: CDMA network planning, for example in 3G UMTS networks, is an important task whether for upgrading existing networks or planning new networks. It is a time consuming, computationally hard, task and generally requires the consideration of both downlink and uplink requirements. Simulation experiments presented here suggest that if time is a major consideration in the planning process then as a compromise only uplink needs to be considered.
Culture and Organizational Improvisation in UK Financial Services  [PDF]
Stephen A. Leybourne
Journal of Service Science and Management (JSSM) , 2009, DOI: 10.4236/jssm.2009.24029
Abstract: This paper considers certain aspects of a four-year program of research, and addresses the changing cultural requirements to support the rise of improvisational working practices within the UK financial services sector. Specifically, it reports on some of the outcomes of a study encompassing over 100 hours of interviews, together with a variety of other primary and secondary data. The outcomes of the full study are documented elsewhere, and they identify a number of key factors that contribute to the successful use and control of improvisational working practices. One of these factors is a supportive organizational culture, and this specific area is dealt with in this paper. A particular focus is how the sample of organizations has attempted to identify and create supportive cultural conditions for improvisational work to take place. In order to bring clarity to the outcomes of this study, a matrix of the case study organizations is also offered, which segregates those organizations according to their cultural support for improvisation and apparent improvisation effectiveness. Some comment on the current difficulties in the Financial Services sector has also been included, as it could be argued that improvisation may have contributed to shortcomings in control processes by members of that sector.
Parallel Evaluation of a Spatial Traversability Cost Function on GPU for Efficient Path Planning  [PDF]
Stephen Cossell, Jose Guivant
Journal of Intelligent Learning Systems and Applications (JILSA) , 2011, DOI: 10.4236/jilsa.2011.34022
Abstract: A parallel version of the traditional grid based cost-to-go function generation algorithm used in robot path planning is introduced. The process takes advantage of the spatial layout of an occupancy grid by concurrently calculating the next wave front of grid cells usually evaluated sequentially in traditional dynamic programming algorithms. The algorithm offers an order of magnitude increase in run time for highly obstacle dense worst-case environments. Efficient path planning of real world agents can greatly increase their accuracy and responsiveness. The process and theoretical analysis are covered before the results of practical testing are discussed.
Quasi-Kernels for Oriented Paths and Cycles  [PDF]
Stephen Bowser, Charles Cable
Open Journal of Discrete Mathematics (OJDM) , 2012, DOI: 10.4236/ojdm.2012.22010
Abstract: If D is a digraph, then K∈V(D) is a quasi-kernel of D if D[K]is discrete and for each y∈V(D)-K there is x∈K such that the directed distance from y to x is less than three. We give formulae for the number of quasi-kernels and for the number of minimal quasi-kernels of oriented paths and cycles.
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