Central Nervous System Infections

RABIES

Tetanus Trismus

Meningitis Bacterial Viral

Predisposing factors Most cases of meningitis occur when colonization by potential pathogens is followed by mucosal invasion of the nasopharynx However, some patients develop disease by direct extension of bacteria across a skull fracture in the area of the cribriform plate Other patients develop meningitis following systemic bacteremia as with endocarditis or a urinary tract infection or pneumonia Some Other predisposing conditions include complement deficiency, corticosteroid excess, and HIV infection

CLINICAL FEATURES The overwhelming majority of patients with bacterial meningitis have fever and headache Most patients have high fevers, but a small percentage have hypothermia CNS symptoms  Some patients will have significant photophobia and/or clouding of the sensorium  Changes in level of consciousness, seizures tend to appear later in the course of disease

Treatment and prevention of bacterial meningitis Suspected bacterial meningitis is a medical emergency and immediate diagnostic steps must be taken to establish the specific cause The mortality rate of untreated bacterial meningitis approaches 100 percent and, even with optimal therapy, there is a high failure rate Empiric treatment should be begun as soon as the diagnosis is suspected using bactericidal agent(s) that achieve significant levels in the CSF

Use of bactericidal agents Bactericidal therapy is generally necessary to cure meningitis Chloramphenicol is a bacteriostatic drug for most enteric Gram negative rods; however, it is usually bactericidal for H. influenzae, N. meningitidis, and S. pneumoniae and has been extensively and successfully used to treat meningitis caused by these organisms

More severe but less frequent than viral Used to have a high rate of infection caused by Haemophilus influenzae type b. However the wide use of protein-polysaccharide conjugated vaccines has dramatically reduced the incidence of this infection In children Neisseria. meningitidis is the most common cause, followed by Streptococcus pneumoniae In adults up to age 60, S. pneumoniae is most common followed by N. meningitidis Over age 60, most cases are due to S. pneumoniae Bacterial Meningitis

Meningococcal Meningitis Severe acute bacterial infection Neisseria meningitidis Aerobic gram-negative bacteria Serogroups based on characteristics of the polysaccharide capsule Relative importance of serogroups depends on geographic location and other factors (e.g. age)

Meningococcal Disease Pathogenesis Organism colonizes nasopharynx - pili In some persons organism invades bloodstream and meninges Transmission- Respiratory droplets