RESUMEN
OBJECTIVES: The purpose of this study is to define the diagnostic criteria for anterior semicircular canal benign paroxysmal positional vertigo (BPPV) based on clinical data and the available anatomical and pathophysiological data. MATERIAL AND METHOD: Between July 2006 and June 2007, 4320 patients consulting for otoneurological disease were investigated by otological examination, videonystagmography and neurological examination. RESULTS: BPPV was diagnosed in 1430 patients, involving the posterior semicircular canal in 1325 patients, the horizontal semicircular canal in 85 patients, the posterior semicircular canal and ipsilateral anterior (superior) semicircular canal in 19 patients and the anterior semicircular canal only in one patient. In the 20 patients with anterior semicircular canal BPPV, the Dix-Hallpike (DH) test induced ageotropic horizontal torsional nystagmus beating towards the uppermost ear in the lateral supine position with reversal on standing. The modified Epley manoeuvre was effective in 94.1% of cases on the 8th day and in 97.5% of cases at 1 month. DISCUSSION/CONCLUSION: Nystagmus beating towards the uppermost ear on the DH test is consistent with BPPV involving the anterior semicircular canal of the uppermost ear. The torsional component of nystagmus and not just the vertical component must be taken into account to facilitate the diagnosis with videonystagmoscopy glasses and identify the affected side. The anterior semicircular canal is rarely affected due to its anatomical position. Settling of otoconia in this canal requires hyperextension of the head. Treatment is simple, consisting of the modified Epley particle repositioning manoeuvre.
Asunto(s)
Canales Semicirculares/fisiopatología , Vértigo/diagnóstico , Vértigo Posicional Paroxístico Benigno , Electronistagmografía/métodos , Femenino , Humanos , Masculino , Persona de Mediana Edad , Examen Neurológico , Nistagmo Patológico/fisiopatología , Otoscopía , Posicionamiento del Paciente/métodos , Postura/fisiología , Vértigo/fisiopatología , Vértigo/terapia , Grabación en VideoRESUMEN
Atherosclerosis begins as an inflammation in blood vessel walls (intima). The inflammatory response of the organism leads to the recruitment of monocytes. Trapped in the intima, they differentiate into macrophages and foam cells leading to the production of inflammatory cytokines and further recruitment of white blood cells. This self-accelerating process, strongly influenced by low-density lipoproteins (cholesterol), results in a dramatic increase of the width of blood vessel walls, formation of an atherosclerotic plaque and, possibly, of its rupture. We suggest a 2D mathematical model of the initiation and development of atherosclerosis which takes into account the concentration of blood cells inside the intima and of pro- and anti-inflammatory cytokines. The model represents a reaction-diffusion system in a strip with nonlinear boundary conditions which describe the recruitment of monocytes as a function of the concentration of inflammatory cytokines. We prove the existence of travelling waves described by this system and confirm our previous results which suggest that atherosclerosis develops as a reaction-diffusion wave. The theoretical results are confirmed by the results of numerical simulations.
Asunto(s)
Aterosclerosis/fisiopatología , Modelos Cardiovasculares , Colesterol/fisiología , Difusión , Células Espumosas/fisiología , Humanos , Inflamación/fisiopatología , Lipoproteínas LDL/fisiología , Macrófagos/fisiología , Monocitos/fisiología , Análisis Numérico Asistido por Computador , Placa Aterosclerótica/fisiopatología , Tiempo de Reacción , Túnica Íntima/fisiopatologíaRESUMEN
Atherosclerosis is an inflammatory disease. The atherosclerosis process starts when low-density lipoproteins (LDLs) enter the intima of the blood vessel, where they are oxidized (ox-LDLs). The anti-inflammatory response triggers the recruitment of monocytes. Once in the intima, the monocytes are transformed into macrophages and foam cells, leading to the production of inflammatory cytokines and further recruitment of monocytes. This auto-amplified process leads to the formation of an atherosclerotic plaque and, possibly, to its rupture. In this paper we develop two mathematical models based on reaction-diffusion equations in order to explain the inflammatory process. The first model is one-dimensional: it does not consider the intima's thickness and shows that low ox-LDL concentrations in the intima do not lead to a chronic inflammatory reaction. Intermediate ox-LDL concentrations correspond to a bistable system, which can lead to a travelling wave that can be initiated by certain conditions, such as infection or injury. High ox-LDL concentrations correspond to a monostable system, and even a small perturbation of the non-inflammatory case leads to travelling-wave propagation, which corresponds to a chronic inflammatory response. The second model we suggest is two-dimensional: it represents a reaction-diffusion system in a strip with nonlinear boundary conditions to describe the recruitment of monocytes as a function of the cytokines' concentration. We prove the existence of travelling waves and confirm our previous results, which show that atherosclerosis develops as a reaction-diffusion wave. The results of the two models are confirmed by numerical simulations. The latter show that the two-dimensional model converges to the one-dimensional one if the thickness of the intima tends to zero.
Asunto(s)
Aterosclerosis/inmunología , Inflamación/inmunología , Modelos Cardiovasculares , Modelos Inmunológicos , Simulación por Computador , Humanos , Cinética , Lipoproteínas LDL/sangre , Lipoproteínas LDL/inmunología , Túnica Íntima/inmunologíaRESUMEN
When several symbionts infect simultaneously the same host (multiple infections), the interactions between them affect the dynamics of the symbiotic population. Despite their widespread occurrence, associations with multiple vertically transmitted symbionts have attracted little attention. Vertical transmission tends to homogenize the symbiotic population because of the bottleneck that occurs at transmission. However, fitness advantages conferred on the host by the different symbionts or the induction of reproductive manipulations can make it possible for multiple infections to persist. We used a matrix population model to understand the kind of interactions that can emerge between vertically transmitted symbionts in established multiple infections. Selection acts only to maximize the production of multiply-infected offspring. For a wide range of parameters, this condition allows cooperation between symbionts to be selected for, through their co-transmission, even when it generates additional costs for female fecundity, a reduction in individual transmission, or affects the dependence upon other symbionts.
Asunto(s)
Conducta Competitiva/fisiología , Conducta Cooperativa , Modelos Biológicos , Simbiosis/fisiología , Evolución Biológica , Fertilidad/fisiologíaRESUMEN
OBJECTIVES: The purpose of this study was to find cause of dizziness, vertigo and falls in old age and to propose treatment. MATERIAL AND METHODS: The study was conducted from October 2003 to March 2004 with 100 patients over the age of 75 years: 72 women and 28 men. They complained of unsteadiness, vertigo, or falls. RESULTS: In this group of patients, 68% were found to have benign paroxysmal positional vertigo, 9% neurologic problems, 5% Meniere disease, 4% vestibular areflexia, 8% a rare cause such as a psychiatric or vascular disorder, and no cause was found in 6%. The diagnosis of Benign Paroxysmal Positional Vertigo is difficult in the elderly because vertigo is often missing and unsteadiness or falls only feeled. CONCLUSIONS: Our study showed that dizziness or unsteadiness in the elderly must be explored by a complete vestibular examination and treated to improve the well-being of these patients.
Asunto(s)
Accidentes por Caídas/estadística & datos numéricos , Mareo/epidemiología , Vértigo/epidemiología , Anciano , Mareo/etiología , Femenino , Humanos , Masculino , Enfermedad de Meniere/complicaciones , Enfermedad de Meniere/epidemiología , Prevalencia , Reflejo Anormal , Reflejo Vestibuloocular , Factores de Riesgo , Vértigo/etiologíaRESUMEN
Endosymbiotic bacteria are often transmitted vertically from one host generation to the next via oocytes cytoplasm. The generally small number of colonizing bacteria in the oocytes leads to a bottleneck at each generation, resulting in genetic homogenization of the symbiotic population. Nevertheless, in many of the species infected by Wolbachia (maternally transmitted bacteria), individuals do sometimes simultaneously harbor several bacterial strains, owing to the fact that Wolbachia induces cytoplasmic incompatibility (CI) that maintains multiple infections. CI occurs in crosses in which the male is infected by at least one Wolbachia strain that the female lacks, and consequently it favors individuals with the greatest symbiotic diversity. CI results in death of offspring in diploid species. In haplodiploid individuals, unfertilized eggs hatch normally into males and fertilized ones, which would lead to females, either die (female mortality type: FM) or develop into males (male development type: MD). Until now, only one theoretical study, restricted to diploid species, has investigated the associations where multiple CI-inducing Wolbachia co-exist, and explored the conditions under which multiple infections can spread. The consequences of double infections on Wolbachia maintenance in host populations, and the selective pressures to which it is subjected have not yet been analysed. Here, we have re-written a model previously developed for single infection in matrix form, which allows easy extension to multiple infections and introduction of mutant strains. We show that (i) the CI type has a strong influence on invasiveness and maintenance of multiple infections; (ii) double infection lowers the invasion threshold of less competitive strains that hitch-hike with their companion strain; (iii) when multiple infections occur, as in single infections, the strains selected are those which maximize the production of infected offspring; and (iv) for the MD CI type, invasion of mutant strains can carry the whole infection to extinction.