Meningitis

Question 1

Encephalitis organisms

Answer 1

1. Arbovirus (most common): St Louis and California (La Crosse) - mosquito transmitted
2. HSV 1: necrosis and hemorrhage within anterior temporal lobes; RBCs in CSF
3. HHV6: exanthem subitum in children
4. mumps virus
5. measles virus
6. VZV
7. Naegleria fowleri
8. Acanthamoeba
9. Balamuthia mandrillaris - granulomatous amebic encephalitis

Question 2

Aseptic meningitis

Answer 2

1. Usually virus: enteroviruses most common in all age groups - summer and fall
2. HSV2
3. Mumps virus
4. HIV
5. lymphocytic choriomeningitis virus (LCM) - most common cause of aseptic meningitis in winter and spring

Question 3

Bacterial meningitis

Neonates

Answer 3

1. GBS
2. Gram negative aerobic rods (E coli, Klebsiella)
3. Listeria monocytogenes
   
   • extremes of age (< 1 month or older than 70 years)
   • steroid treated patients
   • transplants
   • diabetes mellitus
   • HIV
   • iron overload

Question 4

Bacterial meningitis

Infants and young children and young adults

Answer 4

1. Neisseria meningitides #1
   
   • person to person transmission causes localized outbreaks
   • terminal complement deficiencies (C5 to C9 and properdin) at risk
2. S pneumoniae
3. H influenzae type B (used to be #1 before vaccines)

Question 5

Bacterial meningitis

1. Adults
2. Southeast Asia
3. AIDS
4. Some endemic regions

Answer 5

1. Adults - S pneumoniae
2. Southeast Asia - Streptococcus suis
3. AIDS - S pneumoniae, TB (basilar meningitis), Cryptococcus neoformans
4. Cerebral malaria

Question 6

Meningitis laboratory evaluation

Answer 6

1. CSF
   
   • Aseptic meningitis:
     
     • mild WBC increase with mostly lymphs
     • mild increase in protein
     • normal glucose
   • Bacterial meningitis:
     
     • marked increase in WBC (mainly neuts)
     • glucose decreased
   • Encephalitis: normal to findings of viral meningitis (herpes: bloody CSF, high protein, low glucose)
2. Blood and CSF culture
3. CSF gram stain
4. CSF latex agglutination