5/6 Meningitis (Ch 25) Flashcards
Meningitis: definition?
Two major categories?
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
Causes of pyogenic meningitis (v aseptic)?
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
Causes of aseptic meningitis (v pyogenic)?
Aseptic: Viruses, Drugs, malignancies, autoimm disorders
Viruses: Enteroviruses, Arboviruses, Mumps, Herpes, Varicella Zoster, Adenoviruses, EBV, Parvovirus)
Pyogenic meningitis is commonly referred to as what?
Bacterial meningitis (since most pyogenic meningitis is bacterial)
Aseptic meningitis is commonly referred to as what?
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)
Bacterial meningitis: more prevalent in kids or adults?
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.
Aseptic meningitis:
Common causes of bacterial meningitis by age group:
- Neonates?
- Kids 2m -5y?
- Juveniles/adults (5-65y)?
- Elderly?
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)
Bacterial meningitis: most common pathophysiology?
- Colonization by bacteria
- Bacteremia (w host response, IgG2 antibody)
- Crossing the blood brain barrier to the CNS (and host inflammatory response: release of TNF, IL1)
–> leads to cerebral edema
- Cerebral edema + vasculitis –> diminished cerebral blood flow
Bacterial meningitis: routes of infection other than the most common cause (=bacteremia that crosses the BBB)?
- extension from a local (parameningeal) infection, ie from an infected sinus or brain abscess
- trauma (basilar skull fractures)
- CSF shunts gone awry
Bacterial Meningitis: gross pathology?
- acute purulent inflammatory exudate of leptomeninges (pia and arachnoid)
- subdural effusion (this is usually sterile tho)
- cerebral swelling, hydrocephalus
Bacterial Meningitis: microscopic pathology?
-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
Viral Meningitis: what are some clinical findings that can help you narrow down what virus is responsible?
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)
Kids under 2: what are the most common causes of viral meningitis?
Group B Cocksackie viruses
echoviruses
is there a seasonality to viral meningitis?
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)
Pathophys of enterovirus infections?
- Transmission: fecal-oral
- Gets into oropharynx or ileum
- minor viremia
- systemic lymphoid tissue -> major viremia
- Spread to CNS.
Can we distinguish bacterial from viral meningitis by clinical sx alone?
There’s a lot of overlap, so no.
Though in general bacterial tends to be more severe.
What are the most common s/s of meningitis in an infant (<1yr)?
fever, irritability
also may be vomiting, seizures, poor eating, nuchal rigidity
What are the most common s/s of meningitis in an older child/adult?
fever, h/a, meningismus, n/v
may also be confusion, stiff neck, nuchal rigidity, Kernig’s sign (A), Brudzinski’s sign (B)
What are the most common s/s of meningitis in the elderly?
obtundation (lowered alertness), mental status changes
Sounds kind of like delirium, or a UTI.
First lab test to do if suspected meningitis?
lumbar puncture for CSF.
do it immediately, even if your index of suspicion is low.
what tests do you run on the CSF fluid (there are 5-ish)?
- 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
bacterial meningitis: CSF findings will be what?
- WBCs over 200
- WBC differential is 90% polys
- CSF glucose is low (<40)
- CSF protein is increased
viral meningitis: CSF findings will be what?
- 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
what is the biggest difference between CSF findings for bacterial v viral meningitis?
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
what are 2 ways to isolate enterovirus from CSF? what is the best way?
**-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.
Bacterial meningitis: acute complications? (6)
- seizures
- SIADH
- hydrocephalus
- subdural effusion
- hearing loss
- stroke/hemiparesis
Bacterial meningitis: what is the mortality rate?
what factors does prognosis depend on?
serious neuro sequelae that may occur?
- 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
Viral meningitis: prognosis?
Long term sequelae?
Most infants/kids recover completely within a week
Adults may have more prolonged symptoms, but no long-term sequelae.
what patients are susceptible to chronic viral meningitis?
immunocompromised patients.
pts with agammaglobulinemeila and common variable immunodeficiency are susceptible to recurrent meningitis with enteroviruses.
what do you need to rule out when diagnosing viral/aseptic meningitis? (3 categories)
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)
Treatment for bacterial meningitis?
Principles, drugs?
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.
Management of viral meningitis?
- 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.
Prevention of bacterial meningitis: what is post-exposure prophylaxis?
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)
Immunization for bacterial meningitis?
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)
