Pathophysiology
1) acute suppurative infection within the subarachnoid space 2) common entry site is via nasopharynx
Signs and Symptoms
acute onset of – 1) fever 2) headache 3) lethargy 4) stiff neck 5) seizures 6) stroke 7) nausea 8) vomiting 9) photophobia 10) increased intracranial pressure 11) positive Kernig’s sign 12) positive Brudzinski’s sign 13) subacute – presentation over several days 14) if cause is meningococcemia, diffuse rash that rapidly turns petechial
Characteristic Test Findings
Laboratory – CSF on lumbar puncture – 1) cell count 1,000-10,000 (mostly neutrophils) 2) protein elevated in relation to cell count 3) glucose 40% of normal 4) increased cytokines 5) increased chemokines 6) increased intracranial pressure (>180 mm H2O) 7) if cause is Neisseria meningitidis – positive Schwartzman’s reaction
Histology/Gross Pathology
1) inflammation of meninges 2) cerebral edema
Associated Conditions
1) pneumococcal pneumonia (predisposes to Streptococcus pneumonia) 2) otitis media 3) alcoholism 4) diabetes 5) splenectomy 6) complement deficiency (predisposes to N. meningitides infection) 7) hypogammaglobulinemia
Biochemistry
1) loss of cerebral blood flow autoregulation 2) N. meningitidis releases endotoxin before cell lysis.
Inheritance/Epidemiology
1) highest prevalence in infants 6-12 months of age 2) most common organisms in infants – S. pneumoniae (50%), N. meningitides (25%), group B strep (25%), and Listeria (10%) 3) most common in elderly is S. pneumoniae 4) most common in young adults is N. meningitidis (meningiococcus) 5) most common used to be Haemophilus influenzae but has greatly decreased in incidence since 1987 introduction of vaccine 6) overall incidence is 2.5/100,000 7) Listeria affects mostly elderly and transplant patients
Treatment
1) ceftriaxone 2) vancomycin 3) ampicillin (for Listeria) 4) penicillin (for Neisseria) 5) cephalosporin if hospital acquired and Pseudomonas likely 6) vaccination against some specific capsular groups in meningiococcus cases possible 7) chemoprophylaxis with monocycline eradicates carrier state in meningiococcus 8) aim is to reduce personal contacts with affected individuals 9) repeat lumbar puncture in 48 h to make sure sterilization has occurred
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