Brown: Clinical Aspects of Meningitis Flashcards
Bacterial Meningitis
Definition:
- Definition: inflammation of the meninges; can have both infectious and non-infectious causes
Bacterial Meningitis
Epidemiology
Bacterial:
Viral:
Bacterial: 0.2 cases/100,000 population
• More common in adults than children
• Incidence much higher in DEVELOPING world
Viral: 10.9 cases/100,000 populations
• More common in children in adults
Bacterial Meningitis
Early Disease Process: (5 steps)
- Mucosal invasion
- Local invasion/bacteremia (may be able to make presumptive diagnosis based on blood culture)
- Meningeal invasion across BBB or BCB (most important step- serious 100% of the time)
- Bacterial replication in subarachnoid space
- Release of bacterial components (cell wall, lipo-oligosaccharide), which has direct effects on:
Bacterial Meningitis
Cerebral microvascular endothelium:
Cerebral microvascular endothelium
- Increases BBB permeability
- Results in vasogenic edema
- Overall Result is INCREASED ICP
pg 916
Bacterial Meningitis
Macrophages:
Macrophages
-Release IL-1 and TNF
-Act on cerebral microvascular endothelium (see left) AND result in subarachnoid space inflammation
-Inflammation of subarachnoid space has 2 effects:
1. Interstitial edema: caused by increased resistance to CSF outflow
2.Cytotoxic edema: caused by host response to inflammation
Overall result is INCREASED ICP
pg 916
Bacterial Meningitis
Effects of Increased ICP: (2)
o Decreased cerebral blood flow
o Loss of cerebrovascular autoregulation
Bacterial Meningitis
Mucosal Colonization
Pathogenic Factors :
Host Protective Factors:
Pathogenic Factors:
Fimbriae
Polysaccharide capsule
IgA protease
Host Protective Factors: Mucosal epithelium Secretory IgA Ciliary activity Anti-capsular Abs
Bacterial Meningitis
Intravascular Survival
Pathogenic Factors :
Host Protective Factors:
Pathogenic Factors:
Polysaccharide capsule
Host Protective Factors:
Complement activation
Organism specific Abs
Bacterial Meningitis
Meningeal Invasion
Pathogenic Factors :
Host Protective Factors:
Pathogenic Factors:
Fimbriae
Association with monocytes
Host Protective Factors:
BBB/BCB
Note: once infection is established, this is to our disadvantage because it prevents Abx from entering
Bacterial Meningitis
Survival in Subarachnoid Space
Pathogenic Factors :
Host Protective Factors:
Pathogenic Factors:
Polysaccharide capsule
Host Protective Factors:
Poor opsonic activity of CSF
Note: Once the infection gets here, not a lot we have in the way of defense
Microbiology of Meningitis
<1 month: (3)
o Group B Streptococcus (S.agalactiae)
• Note: can decrease early onset disease by intrapartum prophylaxis of maternal carriers
o E.coli
o Listeria monocytogenes
Microbiology of Meningitis
1-23 months: (5)
o Group B Strep o E.coli o Streptococcus pneumoniae o Haemophilus influenza (may see it before vaccine series is complete) o Neisseria meningitidis
Microbiology of Meningitis
24 months to 18 years: (3)
o Neisseria meningitidis (most common)
o S.pneumoniae
o H.influenzae (only if unvaccinated or immunocompromised for some reason)
Microbiology of Meningitis
18-50 years: (2)
o S.pneumoniae (most common)
o N.meningitidis
Microbiology of Meningitis
≥50 years: (4)
o S.pneumoniae
o N.meningitidis
o L.monocytogenes (considered in immunocompromise or pregnancy)
o Aerobic gram negative bacilli (E.coli, Klebsiella)
Microbiology of Meningitis
Head trauma/post neurosurgery: (3)
o Staphylococcus aureus
o Staphylococcus epidermidis
o Aerobic gram negative bacilli (including Pseudomonas)
Microbiology of Meningitis
Basilar skull fracture/CSF leak
Pt notices:
Microbes: (3)
Basilar skull fracture/CSF leak: head trauma occurs, and during recover patient notices clear drainage out of nose (can be tested for glucose to diagnose as CSF leak); may also be less noticeable (ie. no leakage), and should always be considered in cases of recurrent bacterial meningitis
o S.pneumoniae
o H.influenzae
o Group A, B-hemolytic streptococci
Bacterial Meningitis
Symptoms: (6)
o Headache (due to increased ICP)
o Fever (systemic response to infection- not meningitis specific)
o Neck stiffness (due to inflammation of meninges)
o Photophobia (due to inflammation of meninges)
o N/V (due to increased ICP)
o Change in mental status (generally depressed status)
Bacterial Meningitis
Clinical Findings
Adults: (5)
o Adults: from most common to least common
- Neck stiffness (nuchal ridgidity)
- Fever
- Mental status change
- Focal neurological finding (often due to cerebral vasculitis and infarction)
- Rash (petechial rash seen classically with N.meningitidis, but can be seen with others)
Bacterial Meningitis
Clinical Findings
Children:
o Children:
- Older Children: similar to adults
- Neonates/Infants/Non-Verbal Children: much more subtle presentation
- Fever
- Irritability
- Poor-feeding
- Bulging fontanel (occurs late in infection; want to diagnose before this occurs)
Bacterial Meningitis
Underlying conditions that can predispose to the development of bacterial meningitis
Acute/chronic otitis media/mastoiditis:
Sinusitis:
Pneumonia:
Acute/chronic otitis media/mastoiditis (S.pneumo)
Sinusitis (S.pneumo)
Pneumonia (S.pneumo)
Bacterial Meningitis
Underlying conditions that can predispose to the development of bacterial meningitis
Endocarditis:
Recent/remote head trauma:
o Endocarditis (continuous bacteremia) o Recent/remote head trauma (CSF leak)
Bacterial Meningitis
Underlying conditions that can predispose to the development of bacterial meningitis
Immunsuppression:
Alcoholism:
Immunsuppression
- Particularly humoral immunity defects or splenic dysfunction (encapsulated organisms)
- Deficiency of terminal components of complement
Alcoholism (suppresses the immune system); at risk for Gram negative meningitis- E.coli, Klebsiella)
Bacterial meningitis is a medical emergency: need to move quickly; the diagnosis is made by:
Can also diagnose with:
lumbar puncture
Blood cultures
