Meningitis

• i. Aseptic
  • 1. consists of fever, headache, signs of meningeal irritation, and a predominantly lymphocytic pleocytosis with normal CSF glucose
  • 2. most common agents are enteroviral such as echovirus, coxsackievirus and nonparalytic poliovirus; next most common cause is mumps followed by HSV-2, lymphocytic and adenovirus
    • a. coxsackie viruses typically causes a meningitis or encephalitis in the summer months
      • i. group A – herpangina and rash
      • ii. group B – myalgia
• ii. septic meningitis
  • 1. most common pathogen overall is H.flu
  • 2. most common pathogen amongst adults is S.pneumonia
  • 3. pathogenesis is usually to colonize the nasopharynx
  • 4. neonate (birth to 4 weeks)
    • a. group B streptococcus (GBS), most common (30% mortality)
    • b. E.coli (gram negative bacilli)
    • c. Listeria (treat with ampicillin + gentamycin)
    • d. Treatment: cefotaxime plus ampicillin
  • 5. infant (4-12 weeks)
    • a. S.pneumonia
    • b. Treatment – 3rd generation cephalosporin plus ampicillin
  • 6. young children
    • a. H.flu type b (nasopharynx leading to sepsis leading to menintitis)
      • i. Associated with bilateral subdural effusions
      • ii. Treatment: 3rd generation cephalosporin plus ampicillin and steroid to decrease incidence of post-infectious deafness
  • 7. older children and young adults
    • a. N.meningitiditis (nasopharyngeal colonization leading to sepsis leading to meningitis) (intracellular, Gram negative diplococci)
      • i. Waterhouse-Friderichsen syndrome is meningococcemia with vasomotor collapse, shock, DIC, and diffuse hemorrhages
      • ii. Treatment – penicillin or chloramphenicol
  • 8. adults
    • a. S.pneumonia
      • i. More common in elderly and alcoholics
      • ii. Treament – penicillin
  • 9. post-operative
    • a. S.aureus
  • 10. shunt infection
    • a. S.epidermidis (50-75% of shunt infections) followed by staph aureus and then proprionobacteriums acnes
    • b. Ventroatrial shunts have a higher risk of infection and must be lengthened if the child grows
    • c. 90% of shunt infections will occur within the first 100 days following placement
  • 11. posttraumatic meningitis
    • a. most common organism is strep pneumococcus (even within 24 hours of trauma)
  • 12. subdural empyema
    • a. infection usually originates in the frontal or ethmoid or sphenoid sinuses and in the middle ear and mastoid cells
    • b. most common agents streptococci; anaerobic streptococci or bacteroides
    • c. clinically: fever without nuchal rigidity
  • 13. brain abscess
    • a. the result of a focus of suppuration elsewhere in the body
    • b. 40% due to disease of the paranasal sinuses, middle ear, and mastoid cells; commonly lie in the anterolateral part of the cerebellar hemisphere or in the middle and inferior parts of the temporal lobe above the tentorium
    • c. 33% are due to hematogenous spread usually due to endocarditis or a primary septic focus in the lungs or pleura or a congenital cardiac defect or pulmonary AVM that permits emboli to bypass the pulmonary circulation
      • i. Subacute bacterial endocarditis is not usually the cause of brain abscess but rather the cause of vessel occlusion
    • d. Most common pathogen
      • i. Streptococci that may be combined with bacteroides, propionibactyerium or E.coli
    • e. 20% of cases cannot identify a source but brain abscess is almost never a result of meningitis
  • 14. microscopic findings: intimal infiltration of arteries and leptomeninges by neutrophils and inflammatory cell infiltration and thrombosis of small cortical veins with acute infarction of the surrounding tissue
    • a. also complicated by cerebral edema, obstructive or communicating hydrocephalus, subdural effusions or subdural empyema