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x. ID > 5/6 Meningitis (Ch 25) > Flashcards

5/6 Meningitis (Ch 25) Flashcards

1
Q

Meningitis: definition?

Two major categories?

A

Meningitis = inflammation of the subarachnoid space

(remember PAD: Pia, Arachnoid, Dura so this is between the Pia and the Arachnoid)

Major categories = pyogenic and aseptic

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2
Q

Causes of pyogenic meningitis (v aseptic)?

A

Pyogenic: caused by bacteria and fungi. More severe than aseptic form.

Bacteria: Group B strep, H inf., Strep pneumo, Neisseria meningiditis, Listeria

Fungi: Histoplasma, Coccidiodomyces, Cryptococcus

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3
Q

Causes of aseptic meningitis (v pyogenic)?

A

Aseptic: Viruses, Drugs, malignancies, autoimm disorders

Viruses: Enteroviruses, Arboviruses, Mumps, Herpes, Varicella Zoster, Adenoviruses, EBV, Parvovirus)

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4
Q

Pyogenic meningitis is commonly referred to as what?

A

Bacterial meningitis (since most pyogenic meningitis is bacterial)

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5
Q

Aseptic meningitis is commonly referred to as what?

A

Viral meningitis, since mainly caused by viruses.

(Aseptic meningitis technically means any meningitis that is not bacterial or fungal - which is generally viral but could also be drug rxn, autoimmune, cancer)

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6
Q

Bacterial meningitis: more prevalent in kids or adults?

A

Once a disease of childhood, but with **immunizations for H flu (HIB) and pneumococcus (PCV = **pneumococcal conjugate vaccine), the incidence in childhood has decreased a lot.

Mainly now seen in adults.

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7
Q

Aseptic meningitis:

A
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8
Q

Common causes of bacterial meningitis by age group:

  • Neonates?
  • Kids 2m -5y?
  • Juveniles/adults (5-65y)?
  • Elderly?
A

Common causes of bacterial meningitis by age group (ogod this is painful):

  • Neonates: Listeria, E. Coli, Group B Strep (maternal screening has decreased this) (newborns are beautiful as a “BEL”)
  • Kids 2m -5y: H. influenza, Strep pneumo, Neisseria meningitidis “at this age, many things are“happenin” HPN)
  • Juveniles/adults (5-65y): Strep pneumo, Nisseria “children and adults are guilty of ProcrasinatioN”
  • Elderly: Strep pneumo, Listeria “elderly offers PearLs of wisdom”

When in doubt, guess Strep. (for strep I only put the second word because it’s the only thing name that has multiple subspecies)

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9
Q

Bacterial meningitis: most common pathophysiology?

A
  1. Colonization by bacteria
  2. Bacteremia (w host response, IgG2 antibody)
  3. Crossing the blood brain barrier to the CNS (and host inflammatory response: release of TNF, IL1)

–> leads to cerebral edema

  1. Cerebral edema + vasculitis –> diminished cerebral blood flow
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10
Q

Bacterial meningitis: routes of infection other than the most common cause (=bacteremia that crosses the BBB)?

A
  • extension from a local (parameningeal) infection, ie from an infected sinus or brain abscess
  • trauma (basilar skull fractures)
  • CSF shunts gone awry
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11
Q

Bacterial Meningitis: gross pathology?

A
  • acute purulent inflammatory exudate of leptomeninges (pia and arachnoid)
  • subdural effusion (this is usually sterile tho)
  • cerebral swelling, hydrocephalus
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12
Q

Bacterial Meningitis: microscopic pathology?

A

-leptomeninges infiltrated with bacteria & PMNs

  • pia mater resists bacterial penetration into brain itself…. (not sure how this is a micro finding but ok)
  • cerebral vasculitis, venous thrombophlebitis and arteritis w aneurysms or occlusions
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13
Q

Viral Meningitis: what are some clinical findings that can help you narrow down what virus is responsible?

A

whether the s/s are limited to the CNS or whether they are systemic

If limited to CNS, there are only a few viruses that could be the cause: enteroviruses, arboviruses (insect-borne), and mumps (mostly eradicated)

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14
Q

Kids under 2: what are the most common causes of viral meningitis?

A

Group B Cocksackie viruses

echoviruses

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15
Q

is there a seasonality to viral meningitis?

A

yes there is!

viral/aseptic meningitis tends to occur in summer/fall, which mirrors the enterovirus pattern.

kind of makes sense because two main causes of viral meningitis are enterovirus and arbovirus (insect-borne)

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16
Q

Pathophys of enterovirus infections?

A
  1. Transmission: fecal-oral
  2. Gets into oropharynx or ileum
  3. minor viremia
  4. systemic lymphoid tissue -> major viremia
  5. Spread to CNS.
17
Q

Can we distinguish bacterial from viral meningitis by clinical sx alone?

A

There’s a lot of overlap, so no.

Though in general bacterial tends to be more severe.

18
Q

What are the most common s/s of meningitis in an infant (<1yr)?

A

fever, irritability

also may be vomiting, seizures, poor eating, nuchal rigidity

19
Q

What are the most common s/s of meningitis in an older child/adult?

A

fever, h/a, meningismus, n/v

may also be confusion, stiff neck, nuchal rigidity, Kernig’s sign (A), Brudzinski’s sign (B)

20
Q

What are the most common s/s of meningitis in the elderly?

A

obtundation (lowered alertness), mental status changes

Sounds kind of like delirium, or a UTI.

21
Q

First lab test to do if suspected meningitis?

A

lumbar puncture for CSF.

do it immediately, even if your index of suspicion is low.

22
Q

what tests do you run on the CSF fluid (there are 5-ish)?

A
  • opening pressure during puncture (not sure if there’s a tool for this or if you just pay attention)
  • WBC count & differential
  • Glucose
  • Protein
  • Gram stain and culture
23
Q

bacterial meningitis: CSF findings will be what?

A
  • WBCs over 200
  • WBC differential is 90% polys
  • CSF glucose is low (<40)
  • CSF protein is increased
24
Q

viral meningitis: CSF findings will be what?

A
  • WBC count generally 10-500 (tho has been seen >2000)
  • WBC differential: initially mostly polys, but within 24 h will be <50% polys
  • Glucose normal or low
  • Protein normal or high
25
Q

what is the biggest difference between CSF findings for bacterial v viral meningitis?

A

Biggest distinction seems to be the % of polys in the WBC differential

  • bacterial has >90%
  • viral has predominant polys initially but within 24 h will have <50% polys
26
Q

what are 2 ways to isolate enterovirus from CSF? what is the best way?

A

**-PCR: for enterovirus RNA. quicker, more sensitive than culture. **

-cell culture. enterovirus can be isolated from CSF in 30-40% of cases. likelihood of + culture correlates with CSF WBC count.

27
Q

Bacterial meningitis: acute complications? (6)

A
  • seizures
  • SIADH
  • hydrocephalus
  • subdural effusion
  • hearing loss
  • stroke/hemiparesis
28
Q

Bacterial meningitis: what is the mortality rate?

what factors does prognosis depend on?

serious neuro sequelae that may occur?

A
  • mortality is 20-30% for adults (5% for kids)
  • depends on age, what bacteria, neuro status, CSF glucose
  • Neuro sequelae: hearing loss, vision loss, hemiparesis, cog defects
29
Q

Viral meningitis: prognosis?

Long term sequelae?

A

Most infants/kids recover completely within a week

Adults may have more prolonged symptoms, but no long-term sequelae.

30
Q

what patients are susceptible to chronic viral meningitis?

A

immunocompromised patients.

pts with agammaglobulinemeila and common variable immunodeficiency are susceptible to recurrent meningitis with enteroviruses.

31
Q

what do you need to rule out when diagnosing viral/aseptic meningitis? (3 categories)

A

need to rule out more serious/treatable causes of meningitis that can mimic aseptic presentation:

-parameningeal infections (otitis media, mastoiditis, sinusitis, subdural empyema, brain abscess, epidural abscess)

-tuberculous meningitis, cryptococcal meningitis. persistence of CNS sx over 3d should cause suspicion for these bugs.

-spirochetes (Lyme, syphilis, leptospirosis)

32
Q

Treatment for bacterial meningitis?

Principles, drugs?

A

Principles: achieve CSF concentration of med that is 10x the minimal bactericidal concentration (MBC).

Drugs: Ceftriaxone since usually caused by strep pneumo. Add Vancomycin until the susceptability profile of the strep is known.

33
Q

Management of viral meningitis?

A
  • possible admission to hosp
  • appropriate systemic abx (if viral meningitis occurs in the setting of bacteremia, OR if the meningitis is caused by one of the few bacteria that cause “aseptic” meningitis)
  • Observe
  • Repeat lumbar puncture
  • PCR for enterovirus?
  • experimental anti-viral for enterovirus: pleconaril. reduces headache.
34
Q

Prevention of bacterial meningitis: what is post-exposure prophylaxis?

A

prevention of secondary cases

-people who have come into close contact with pts with meningococcal disease need a short course of antibiotic prophy.

use rifampin (4 doses, 2d) or ciprofloxacin (1 dose)

35
Q

Immunization for bacterial meningitis?

A

regular immunizations for infants with HIB and PCV has decreased incidences a lot

  • immunize people at risk for meningococcal disease (military recruits)
  • immunize people at risk for pneumococcal disease (hemoglobinopathies, splenectomy, cochlear implants)

x. ID (40 decks)

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