A case of neuroleptic malignant syndrome on withdrawal of benzhexol

The neuroleptic malignant syndrome is a rare and potentially lethal reaction which is usually associated with the use of medications with antidopaminergic properties. This article describes the case of an elderly gentleman who developed the neuroleptic malignant syndrome after withdrawal of the anticholinergic agent benzhexol (trihexyphenidyl hydrochloride), which he was taking for Parkinson’s disease. The patient improved rapidly after treatment was restarted. This case adds to the evidence that antidopaminergic agents may not be necessary for the development of this syndrome, and increased awareness of this possibility is advisable in such circumstances.peer-reviewe

Simple measures can improve care in our hospitals : an audit of venous thromboembolism practice

Abstract: Venous thromboembolism (VTE) is a serious but preventable complication of hospitalisation. Doctors still sometimes fail to adhere to them, thus putting patients at risk and incurring considerable expense for the national health service. We chose to audit the practice of doctors in our geriatric facility, and assessed the effect of a memoire to increase compliance. We also explore how our hospitals can learn from the experience of other centres, where the risk of litigation has brought this condition to the forefront. Compliance improved from 30.7% to 63.3%, which was statistically significant. We would suggest that a centralised and organised approach could produce even greater levels of compliance.peer-reviewe

The use of ultrasound in the diagnosis of Tenchkoff catheter tunnel infection

Exit site infections of Tenchkoff catheters in patients on peritoneal dialysis are rather common. These very often remain localised but they may spread along the tunnel of the catheter. These infections are very important to be diagnosed quickly as untreated they usually necessitate the removal of the dialysis catheter. The use of ultrasound to aid diagnosis has been reported in various case studies. We here report the use of ultrasound to aid the diagnosis of a tunnel infection in a patient on peritoneal dialysis.peer-reviewe

Modeling Brain Resonance Phenomena Using a Neural Mass Model

Stimulation with rhythmic light flicker (photic driving) plays an important role in the diagnosis of schizophrenia, mood disorder, migraine, and epilepsy. In particular, the adjustment of spontaneous brain rhythms to the stimulus frequency (entrainment) is used to assess the functional flexibility of the brain. We aim to gain deeper understanding of the mechanisms underlying this technique and to predict the effects of stimulus frequency and intensity. For this purpose, a modified Jansen and Rit neural mass model (NMM) of a cortical circuit is used. This mean field model has been designed to strike a balance between mathematical simplicity and biological plausibility. We reproduced the entrainment phenomenon observed in EEG during a photic driving experiment. More generally, we demonstrate that such a single area model can already yield very complex dynamics, including chaos, for biologically plausible parameter ranges. We chart the entire parameter space by means of characteristic Lyapunov spectra and Kaplan-Yorke dimension as well as time series and power spectra. Rhythmic and chaotic brain states were found virtually next to each other, such that small parameter changes can give rise to switching from one to another. Strikingly, this characteristic pattern of unpredictability generated by the model was matched to the experimental data with reasonable accuracy. These findings confirm that the NMM is a useful model of brain dynamics during photic driving. In this context, it can be used to study the mechanisms of, for example, perception and epileptic seizure generation. In particular, it enabled us to make predictions regarding the stimulus amplitude in further experiments for improving the entrainment effect

Period-Adding Bifurcations in a One Parameter Family of Interval Maps

The dynamics and bifurcations of a one-parameter family of interval maps with a single jump discontinuity are studied. The central assumptions are that the maps are injective, increasing to the left of the discontinuity and decreasing to the right. It is shown that such maps have only periodic orbits of periods n; n+1; 2n, and 2n+2 with at least one of these being attracting. The value of n depends on the preimages of the discontinuity. Two types of bifurcations occur when an iterate of the discontinuity is mapped onto itself. In one type of bifurcation, a period n + 1 orbit emerges to coexist with a preexisting period n orbit. In the other type, the period n orbit disappears leaving a period n + 1 orbit. Generically, these two bifurcations must alternate, giving regions of coexistence and a global period-adding genealogy. keywords: bifurcation, period-adding Running Title: Period-adding Bifurcations 1 Introduction In this paper we discuss the dynamics and bifurcations of a one-p..

IDEA: Internet Differential Equations Activities

Interdisciplinary computer-based activities for differential equations: a database of computer activities illustrating both mathematical concepts and the application of these concepts in a wide variety of disciplines. DynaSys, Java differential equations software that can be used to implement many of the activities, is available for downloading. Current project topics include: basic ecological models; bungee jumping; El Nino; irrigation and conservation; mathematical models of neurons; oscillating chemical reactions; rangeland ecosystems; salmon migration; small mammal dispersion; and discrete dynamics on the real line and in the complex plane. With a list of other Internet DiffEQ links

Compression and Model Reduction: A Case Study

We discuss a method by which the dynamics of a network of coupled neurons can be captured in a one-dimensional map. The network used as an example of this technique consists of a pair of neurons, one of which is an endogenous burster and the other excitable, but not bursting in the absence of phasic input. The reduction is accomplished by decomposing the flow into fast and slow subsystems, each operating on a distinct time scale. A "map of knees" is constructed using singular perturbation techniques. A concise expression for this map is developed by introducing time coordinates to each stable branch of the slow manifold. The compression associated with the fast subsystem is used to determine the qualitative properties of the map. 1 Introduction In this paper we illustrate, by way of example, a method to capture the dynamics of a network of voltage-gated conductance equations in a low-dimensional map. This technique utilizes ideas from geometric singular perturbation theory to decompos..

Population Models of Genomic Imprinting. II. Maternal and Fertility Selection

Under several hypotheses for the evolutionary origin of imprinting, genes with maternal and reproductive effects are more likely to be imprinted. We thus investigate the effect of genomic imprinting in single-locus diallelic models of maternal and fertility selection. First, the model proposed by Gavrilets for maternal selection is expanded to include the effects of genomic imprinting. This augmented model exhibits novel behavior for a single-locus model: long-period cycling between a pair of Hopf bifurcations, as well as two-cycling between conjoined pitchfork bifurcations. We also examine several special cases: complete inactivation of one allele and when the maternal and viability selection parameters are independent. Second, we extend the standard model of fertility selection to include the effects of imprinting. Imprinting destroys the “sex-symmetry” property of the standard model, dramatically increasing the number of degrees of freedom of the selection parameter set. Cycling in all these models is rare in parameter space

Non-malignant CSF lymphocytosis in a patient with acute lymphoblastic leukemia

Patients with haematological malignancy are often profoundly immune suppressed, and more so if they require more than one line of therapy. Infection should always be considered when they become unwell. We discuss the differential diagnoses of a young man with multiply-relapsed Philadelphia chromosome-positive B-cell acute lymphoblastic leukaemia who presented with neurological symptoms and cerebrospinal fluid lymphocytosis. The diagnostic approach needs to be rapid and structured, and may require microbiology and neurology support. Keywords: CSF lymphocytosis, Lymphocytic pleocytosis, Varicella zoster encephalitis, Inotuzumab, Relapsed leukemi

The Temporal Dynamics of Cortical Normalization Models of Decision-making

Normalization is a widespread neural computation in both early sensory coding and higher-order processes such as attention and multisensory integration. It has been shown that during decision-making, normalization implements a context-dependent value code in parietal cortex. In this paper we develop a simple differential equations model based on presumed neural circuitry that implements normalization at equilibrium and predicts specific time-varying properties of value coding. Moreover, we show that when parameters representing value are changed, the solution curves change in a manner consistent with normalization theory and experiment. We show that these dynamic normalization models naturally implement a time-discounted normalization over past activity, implying an intrinsic reference-dependence in value coding of a kind seen experimentally. These results suggest that a single network mechanism can explain transient and sustained decision activity, reference dependence through time discounting, and hence emphasizes the importance of a dynamic rather than static view of divisive normalization in neural coding