Meningitis Flashcards
Is bacterial or viral meningitis more common? Who is each more common in?
Viral meningitis is more common
Viral is more common in children, and bacterial is more common in adults since introduction of the Hib vaccine
As bacteria replicate in the subarachnoid space, what are two major effects the release of bacterial components (i.e. LPS) will cause?
- Dilation of cerebral microvascular epithelium
2. Stimulation of macrophages and neutrophils, which release inflammatory cytokines
What is vasogenic edema?
Edema caused by increased permeability of blood brain barrier, leads to increased ICP, especially due to exit of proteins from the blood into the CSF leading to increased oncotic pressure
Basically, edema caused by “vaso” or vessels opening
What is interstitial edema?
Increased resistance to CSF outflow due to inflammation of the subarachnoid space leads to increased ICP and breakage of blood-CSF barrier, but will NOT cause a protein increase
Basically, edema caused by excess CSF
What is cytotoxic edema?
Increased intracellular pressure buildup due to loss of ion gradients, often following subarachnoid inflammation
Basically, edema within the neuronal cell rather than interstitial space
Why is increased ICP really a problem?
Leads to decreased cerebral blood flow and loss of cerebrovascular autoregulation
What can extended subarachnoid space inflammation due to the blood vessels in the brain?
Causes cerebral vasculitis
What is the main pathogenic factor that facilitates entrance into the CSF? What is the host defense?
Fimbriae, and association with macrophages
Host defense: Blood-CSF barrier
What is the main pathogenic factor that allows survival in the CSF? What is the host defense?
Polysaccharide capsule
Host defense would be humoral + complement-mediated, however there is poor antibodies in the CSF so there is no defense!
What is the difference between early and late onset GBS infection?
Early: <7 days, highly preventable
Late: Nosocomial or community-borne (up to 1 month)
What are the top 5 microbes causing CNS infection in 1-23 month olds?
- Group B strep
- E. coli K1
(listeria falls off the list) - Strept pneumoniae
- Hib (vaccine not completed yet)
- Neisseria meningitidis
What are the top 2 microbes causing meningitis from 2 years to 18 years?
- N. meningitidis (most common cause among teens)
2. S. pneumoniae
What are the top 2 microbes causing meningitis from 18 to 50 years?
- S. pneumoniae (most common cause among adults)
2. N. meningitides
How do the microbes causing meningitis differ past age 50?
Same top two, but a return of Listeria (immunocompromization with age) and aerobic gram negatives like E. coli
What species most commonly cause meningitis following head trauma / post neurosurgery?
Staphylococcus aureus and epidermitis.
Aerobic gram negatives as well including P. aeruginosa and E. coli
What causes meningitis in basilar skull fracture / CSF leak?
S. pneumonia
H. influenza
Group A Strept
What are the most common clinical findings of meningitis in adults?
Neck stiffness (nuchal rigidity), fever, mental status change (depression), focal neurologic finding (indicates cerebral vasculitis), or rash (from Neisseria meningitidis)
How do neonates / infants / non-verbal children present differently with meningitis than adults?
More subtle presentation, including fever, irritability, poor feeding, and bulging fontanelle is an important finding
What are important predisposing factors to meningitis?
OPS of MOPS, although direct seeding has not been shown,
Endocarditis, recent head trauma / CSF leak, immunosuppression or splenic dysfunction, alcoholism, complement deficiency
What complement deficiency puts you at a greater risk for meningitis?
Deficiency of C5-C9 (think Noir 5-9pm)
What is done to diagnose meningitis?
Lumbar puncture
What is needed to be done before LP in some patients?
Neuroimaging (CT) scan, especially in immunocompromised or when we’re concerned for stroke
What are typical parameters you want to measure from CSF?
- Opening pressure (ICP)
- Protein
- Glucose (with comparative simultaneous serum glucose)
- Cell count
- Bacteria / viral detection
What is typically used for bacterial and viral detection?
Bacteria - latex agglutination, gram stain, or multiplex PCR
Viral - PCR
Other than antibiotics which penetrate CSF well, what other drugs do we give patients with meningitis and why?
Corticosteroids - reduce inflammation to reduce ICP and prevent sensorineural hearing loss
What is used to prevent meningitis?
Antibiotic prophylaxis for close contacts (Rifampin)
Vaccines including meningococcal, Hib, pneumococcal, and GBS antibiotics in pregnancy
What is pleocytosis?
Increased number of WBCs in CSF
What is the characteristic pleocytosis in aseptic meningitis?
Predominantly lymphocytic (T/B cells), with bacterial stain and cultures being negatively
What is the most common cause of viral meningitis and who gets it?
Typically associated with enteroviruses, most common in infants / young children in late summer and early fall
What WBC type are bacterial infections most likely to have in the CSF and how high is the total count?
Usually over >1,000 WBCs per mL, with >50% being PMNs
What WBC type are viral infections most likely to have in the CSF and how high is the total count?
Usually over >1,000 WBCs per mL, with <50% being PMNs, except in early stages
Are you expected to have increased protein in viral meningitis?
No, or only slightly elevated.
Only bacterial infections have >100 mg/dl protein
What is the expected CSF vs serum glucose in bacterial meningitis?
<50% of serum glucose, important to get simultaneous glucose especially in diabetics
What are some non-infectious causes to meningitis?
Autoimmune diseases like Lupus and Rheumatoid arthritis
Drugs such as NSAIDS, TMP/SMX, carbamazepine
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