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1、Bacterial meningitis,站,Introduction,Bacterial meningitis is an inflammation of the leptomenings, usually causing by bacterial infection. Bacterial meningitis may present acutely (symptoms evolving rapidly over 1-24 hours), subacutely (symptoms evolving over 1-7days), or chronically (symptoms evolvin
2、g over more than 1 week).,Introduction,Annual incidence in the developed countries is approximately 5-10 per 100000. 30000 infants and children develop bacterial meningitis in United States each year. Approximately 90 per cent of cases occur in children during the first 5 years of life.,Introduction
3、,Cases under age 2 years account for almost 75% of all cases and incidence is the highest in early childhood at age 6-12 months than in any other period of life. There are significant difference in the incidence of bacterial meningitis by season.,Etiology,Causative organisms vary with patient age, w
4、ith three bacteria accounting for over three-quarters of all cases: Neisseria meningitidis (meningococcus) Haemophilus influenzae (if very young and unvaccinated) Streptococcus pneumoniae ( pneumococcus),Etiology,Other organisms Neonates and infants at age 2-3 months Escherichia coli B-haemolytic st
5、reptococci Staphylococcus aureus Staphylococcus epidermidis Listeria monocytogenes,Etiology,Elderly and immunocompromised Listeria monocytogenes Gram negative bacteria Hospital-acquired infections Klebsiella Escherichia coli Pseudomonas Staphylococcus aureus,Etiology,The most common organisms Neonat
6、es and infants under the age of 2months Escherichia coli Pseudomonas Group B Streptococcus Staphylococcus aureus,Etiology,Children over 2 months Haemophilus influenzae type b Neisseria meningitidis Streptococcus pneumoniae Children over 12 years Neisseria meningitidis Streptococcus pneumoniae,Etiolo
7、gy,Major routes of leptomening infection Bacteria are mainly from blood. Uncommonly, meningitis occurs by direct extension from nearly focus (mastoiditis, sinusitis) or by direct invasion (dermoid sinus tract, head trauma, meningo-myelocele).,Pathogenesis,Susceptibility of bacterial infection on CNS
8、 in the children Immaturity of immune systems Nonspecific immune Insufficient barrier (Blood-brain barrier) Insufficient complement activity Insufficient chemotaxis of neutrophils Insufficient function of monocyte-macrophage system Blood levels of diminished interferon (INF) -and interleukin -8 ( IL
9、-8 ),Pathogenesis,Susceptibility of bacterial infection on CNS in the children Specific immune Immaturity of both the cellular and humoral immune systems Insufficient antibody-mediated protection Diminished immunologic response Bacterial virulence,Pathogenesis,A offending bacterium from blood invade
10、s the leptomeninges. Bacterial toxics and Inflammatory mediators are released. Bacterial toxics Lipopolysaccharide, LPS Teichoic acid Peptidoglycan Inflammatory mediators Tumor necrosis factor, TNF Interleukin-1, IL-1 Prostaglandin E2, PGE2,Pathogenesis,Bacterial toxics and inflammatory mediators ca
11、use suppurative inflammation. Inflammatory infiltration Vascular permeability alter Tissue edema Blood-brain barrier detroy Thrombosis,Pathology,Diffuse bacterial infections involve the leptomeninges, arachnoid membrane and superficial cortical structures, and brain parenchyma is also inflamed. Meni
12、ngeal exudate of varying thickness is found. There is purulent material around veins and venous sinuses, over the convexity of the brain, in the depths of the sulci, within the basal cisterns, and around the cerebellum, and spinal cord may be encased in pus. Ventriculitis (purulent material within t
13、he ventricles) has been observed repeatedly in children who have died of their disease.,Pathology,Invasion of the ventricular wall with perivascular collections of purulent material, loss of ependymal lining, and subependymal gliosis may be noted. Subdural empyema may occur. Hydrocephalus is an comm
14、on complication of meningitis. Obstructive hydrocephalus Communicating hydrocephalus,Pathology,Blood vessel walls may infiltrated by inflammatory cells. Endothelial cell injury Vessel stenosis Secondary ischemia and infarction Ventricle dilatation which ensues may be associated with necrosis of cere
15、bral tissue due to the inflammatory process itself or to occlusion of cerebral veins or arteries.,Pathology,Inflammatory process may result in cerebral edema and damage of the cerebral cortex. Conscious disturbance Convulsion Motor disturbance Sensory disturbance Meningeal irritation sign is found b
16、ecause the spinal nerve root is irritated. Cranial nerve may be damaged,Clinical manifestation,Bacterial meningitis may present acutely (symptoms evolving rapidly over 1-24 hours) in most cases. Symptoms and signs of upper respiratory or gastrointestinal infection are found before several days when the clnical manifestations of bacterial meningitis happen. Some patients may access suddenly with shock and DIC.,Clinical manifestation,Toxic symptom all over the body Hyperpyrexia Headache Photopho
