D. H. Duong

Bio: D. H. Duong is an academic researcher from Washington University in St. Louis. The author has contributed to research in topics: Subarachnoid hemorrhage & Vasospasm. The author has an hindex of 13, co-authored 18 publications receiving 1231 citations. Previous affiliations of D. H. Duong include MedStar Washington Hospital Center & University of Washington Medical Center.

Controlling chaos in the brain

Abstract: In a spontaneously bursting neuronal network in vitro, chaos can be demonstrated by the presence of unstable fixed-point behaviour. Chaos control techniques can increase the periodicity of such neuronal population bursting behaviour. Periodic pacing is also effective in entraining such systems, although in a qualitatively different fashion. Using a strategy of anticontrol such systems can be made less periodic. These techniques may be applicable to in vivo epileptic foci.

Characteristics of ventricular shunt malfunctions among patients with neurocysticercosis.

Abstract: OBJECTIVE: Ventricular shunts used to relieve hydrocephalus among patients with neurocysticercosis have been plagued by high shunt malfunction rates We examined the characteristics of shunt malfunctions among patients with neurocysticercosis METHODS: This is a retrospective chart review of data for 122 patients who were admitted with a diagnosis of cysticercosis during a 55-year period Cases of hydrocephalus requiring shunt placement were reviewed with respect to the segment of shunt obstruction, disease activity at the time of shunt placement, and the effects of antihelminthic treatment on shunt failures and longevity RESULTS: Twenty-one patients required 49 operations for relief of hydrocephalus, including 22 new shunt placements, 23 revisions, and 4 cyst extirpations Of these shunt failures, 78% occurred within the first 12 months and 96% within 3 years Of the failures that occurred in the distal segment, 75% occurred within 6 months By comparison, 33% of proximal segment obstructions and 50% of the total number of valve obstructions occurred within the first 6 months Of the shunts placed during the vesicular stage of infection, 63% required revisions, compared with 29% of those placed during the colloidal through calcified stages Nineteen shunts were placed during the vesicular stage, and nine patients received a full course of antihelminthic treatment after shunt placement In less than 6 months, 33% of the cases involving shunt placement followed by antihelminthic treatment exhibited shunt failure, compared with 90% of the cases without antihelminthic treatment (P < 005, X 2 test) CONCLUSION: Among patients with vesicular stage cysticercosis, placement of a ventriculoperitoneal shunt followed by a course of antihelminthic medication seems to promote shunt longevity

Time-related patterns of ventricular shunt failure

Abstract: Proximal obstruction is reported to be the most common cause of ventriculoperitoneal (VP) shunt failure, suggesting that imperfect ventricular catheter placement and inadequate valve mechanisms are major causes This study retrospectively examined patterns of shunt failure in 128 consecutive patients with symptoms of shunt malfunction over a 2-year period Factors analyzed included site of failure, time from shunt placement or last revision to failure, age of patient at time of failure, infections, and primary etiology of the hydrocephalus One hundred of these patients required revisions; 14 revisions were due to infections In this series there was a higher incidence of distal (43%) than of proximal (35%) failure The difference was not statistically significant when the overall series was considered; however, when factoring time to failure as a variable, marked differences were noted regardless of the underlying cause of hydrocephalus or the age of the patient Of the 49 patients needing a shunt revision or replacement within 2 years of the previous operation, 50% had proximal malfunction, 14% distal, and 10% had malfunctions attributable directly to the valve itself Also, 12 of the 14 infections occurred during this time interval In sharp contrast, of the 51 patients having shunt failure from 2 to more than 12 years after the previous procedure, 72% had distal malfunction, 21% proximal, and only 6% had a faulty valve or infection This difference between time to failure for proximal versus distal failures was statistically significant (P < 000001 for both Student's t-test and non-parametric Mann-Whitney U-test)(ABSTRACT TRUNCATED AT 250 WORDS)

Use of Intra-Aortic Balloon Pump Counterpulsation for Refractory Symptomatic Vasospasm

Abstract: ¶ Delayed neurologic deficits secondary to vasospasm remain a vexing problem. Current treatments include: hypertensive hypervolemic hemodilution (Triple-H) therapy, angioplasty, and intra-arterial papaverine administration. Significant morbidity and mortality still result from vasospasm despite these therapies. We present two patients with symptomatic vasospasm who received intra-aortic balloon pump counterpulsation (IABP) to improve cerebral blood flow when they were unable to tolerate Triple-H therapy. One patient (L.T.) developed vasospasm after resection of a meningioma that encased the carotid and middle cerebral artery. The other patient (D.F.) suffered a subarachnoid hemorrhage (Fisher Grade III, Hunt/Hess Grade III) from a basilar tip aneurysm. Postoperatively, both patients developed vasospasm. Treatment with Triple-H therapy, angioplasty, and papaverine yielded modest results. When they experienced cardiac ischemia, Triple-H therapy was stopped, but their neurologic condition deteriorated markedly. Because of this, IABP was started. Both patients had an immediate improvement in cardiac function. IABP was able to reverse some of the neurologic deficits, and was weaned off after several days of support. Both patients had a substantial improvement in function, and are now capable of caring for themselves. We conclude that IABP may play an important role for improving cerebral blood flow in patients with vasospasm. It may be particularly useful in those patients with limited cardiac reserve.

Postoperative hydrocephalus in cranial base surgery.

Abstract: The incidence of postoperative hydrocephalus and factors relating to it were analyzed in 257 patients undergoing cranial base surgery for tumor resection. A total of 21 (8%) patients developed postoperative hydrocephalus, and all required shunting, Forty-two (17%) patients developed cerebrospinal fluid (CSF) leak that required placement of external drainage systems (ventriculostomy or lumbar drain, or both); 10 (23%) of these 42 patients eventually needed shunt placement to stop the leak because of hydrocephalus. Prior craniotomy, prior radiation therapy, and postoperative CSF infection were also associated with an increased risk of developing hydrocephalus (48% versus 6%, 19% versus 8%, and 14% versus 7%, respectively). Prior radiation and postoperative CSF infection increased the risk of CSF leak in patients with hydrocephalus (30% versus 18% and 30% versus 9%, respectively). CSF leak and hydrocephalus commonly occurred in patients who underwent resection of a glomus tumor. In conclusion, 8% of patients who underwent cranial base surgery for tumors developed de novo hydrocephalus; half of them also had CSF leak in addition to hydrocephalus; and all required shunt placement for CSF diversion.

Synchronization and rhythmic processes in physiology

Abstract: Complex bodily rhythms are ubiquitous in living organisms. These rhythms arise from stochastic, nonlinear biological mechanisms interacting with a fluctuating environment. Disease often leads to alterations from normal to pathological rhythm. Fundamental questions concerning the dynamics of these rhythmic processes abound. For example, what is the origin of physiological rhythms? How do the rhythms interact with each other and the external environment? Can we decode the fluctuations in physiological rhythms to better diagnose human disease? And can we develop better methods to control pathological rhythms? Mathematical and physical techniques combined with physiological and medical studies are addressing these questions and are transforming our understanding of the rhythms of life.

Foundations of neural networks, fuzzy systems, and knowledge engineering

Abstract: From the Publisher: "Covering the latest issues and achievements, this well documented, precisely presented text is timely and suitable for graduate and upper undergraduate students in knowledge engineering, intelligent systems, AI, neural networks, fuzzy systems, and related areas. The author's goal is to explain the principles of neural networks and fuzzy systems and to demonstrate how they can be applied to building knowledge-based systems for problem solving. Especially useful are the comparisons between different techniques (AI rule-based methods, fuzzy methods, connectionist methods, hybrid systems) used to solve the same or similar problems." -- Anca Ralescu, Associate Professor of Computer Science, University of Cincinnati Neural networks and fuzzy systems are different approaches to introducing human-like reasoning into expert systems. This text is the first to combine the study of these two subjects, their basics and their use, along with symbolic AI methods to build comprehensive artificial intelligence systems. In a clear and accessible style, Kasabov describes rule- based and connectionist techniques and then their combinations, with fuzzy logic included, showing the application of the different techniques to a set of simple prototype problems, which makes comparisons possible. A particularly strong feature of the text is that it is filled with applications in engineering, business, and finance. AI problems that cover most of the application-oriented research in the field (pattern recognition, speech and image processing, classification, planning, optimization, prediction, control, decision making, and game simulations) are discussed and illustrated with concrete examples. Intended both as a text for advanced undergraduate and postgraduate students as well as a reference for researchers in the field of knowledge engineering, Foundations of Neural Networks, Fuzzy Systems, and Knowledge Engineering has chapters structured for various levels of teaching and includes original work by the author along with the classic material. Data sets for the examples in the book as well as an integrated software environment that can be used to solve the problems and do the exercises at the end of each chapter are available free through anonymous ftp.