5/6 Meningitis (Ch 25)

Question 1

Meningitis: definition?

Two major categories?

Answer 1

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

Question 2

Causes of pyogenic meningitis (v aseptic)?

Answer 2

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

Question 3

Causes of aseptic meningitis (v pyogenic)?

Answer 3

Aseptic: Viruses, Drugs, malignancies, autoimm disorders

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

Question 4

Pyogenic meningitis is commonly referred to as what?

Answer 4

Bacterial meningitis (since most pyogenic meningitis is bacterial)

Question 5

Aseptic meningitis is commonly referred to as what?

Answer 5

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)

Question 6

Bacterial meningitis: more prevalent in kids or adults?

Answer 6

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.

Question 7

Aseptic meningitis:

Question 8

Common causes of bacterial meningitis by age group:

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

Answer 8

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)

Question 9

Bacterial meningitis: most common pathophysiology?

Answer 9

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

4. Cerebral edema + vasculitis –> diminished cerebral blood flow

Question 10

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

Answer 10

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

Question 11

Bacterial Meningitis: gross pathology?

Answer 11

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

Question 12

Bacterial Meningitis: microscopic pathology?

Answer 12

-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

Question 13

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

Answer 13

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)

Question 14

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

Answer 14

Group B Cocksackie viruses

echoviruses

Question 15

is there a seasonality to viral meningitis?

Answer 15

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)

Question 16

Pathophys of enterovirus infections?

Answer 16

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

Question 17

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

Answer 17

There’s a lot of overlap, so no.

Though in general bacterial tends to be more severe.

Question 18

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

Answer 18

fever, irritability

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

Question 19

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

Answer 19

fever, h/a, meningismus, n/v

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

Question 20

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

Answer 20

obtundation (lowered alertness), mental status changes

Sounds kind of like delirium, or a UTI.

Question 21

First lab test to do if suspected meningitis?

Answer 21

lumbar puncture for CSF.

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

Question 22

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

Answer 22

• 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

Question 23

bacterial meningitis: CSF findings will be what?

Answer 23

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

Question 24

viral meningitis: CSF findings will be what?

Answer 24

• 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

Question 25

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

Answer 25

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

Question 26

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

Answer 26

**-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.

Question 27

Bacterial meningitis: acute complications? (6)

Answer 27

- seizures - SIADH - hydrocephalus - subdural effusion - hearing loss - stroke/hemiparesis

Question 28

Bacterial meningitis: what is the mortality rate? what factors does prognosis depend on? serious neuro sequelae that may occur?

Answer 28

- 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

Question 29

Viral meningitis: prognosis? Long term sequelae?

Answer 29

Most **infants/kids** recover completely within a week **Adults** may have more prolonged symptoms, but no long-term sequelae.

Question 30

what patients are susceptible to chronic viral meningitis?

Answer 30

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

Question 31

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

Answer 31

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)

Question 32

Treatment for bacterial meningitis? Principles, drugs?

Answer 32

_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.

Question 33

Management of viral meningitis?

Answer 33

- 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.

Question 34

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

Answer 34

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)

Question 35

Immunization for bacterial meningitis?

Answer 35

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)