05-6 Meningitis (Ch 25) Flashcards
A. Understand the spectrum of infectious causes of meningitis. B. Understand the pathophysiology of bacterial meningitis, including the effect of infection on cerebral blood flow. C. Understand the importance of early recognition of meningitis and the approach to diagnosis and management. (25 cards)
meningitis definition vs. pyogenic meningitis
Meningitis is a clinical and pathological term used to identify disease caused by inflammation of the subarach- noid space. It is defined clinically by demonstration of inflammatory changes or isolation of a pathogenic mi- crobe from the cerebrospinal fluid (CSF). In general bacteria, fungi, and some protozoa cause a more serious, life-threatening form of meningitis that can collectively be termed pyogenic meningitis
Fungi that cause pyogenic meningitis
Histoplasma capsulatum
Coccidiodomyces immitus
Cryptococcus neoformans
Amoeba that cause pyogenic meningitis
Naegleria sp.
What categories of pathogens/procedures/maladies cause aseptic meningitis?
Literally, the term aseptic meningitis refers to subarachnoid inflammation from any cause other than pyogenic bacteria or fungi. The differential includes viruses, certain bacterial and fungal infections where the pathogen may be difficult to isolate from the CSF, other microorganisms, and non-infectious causes.
—Most cases are viral, so aseptic meningitis and viral meningitis are often used synonymously.
—Aseptic meningitis is generally less severe.
Bacteria that cause meningitis in 0-2 month olds?
group B streptococci
E. coli
Listeria monocytogenes
Bacteria that cause meningitis in 2 month to 5 year olds?
Streptococcus pneumoniae
Neisseria meningitidis
Haemophilus influenzae (less common now w/ vaccination)
Bacteria that cause meningitis in 5-60 year olds?
Streptococcus pneumoniae
Neisseria meningitidis
Bacteria that cause meningitis in >60 year olds?
Streptococcus pneumoniae
Listeria monocytogenes
Bacteria that cause meningitis in immunocompromised patients?
Listeria monocytogenes
Cryptococcus neoformans
Bacteria that cause meningitis s/p basilar skull fx?
Streptococcus pneumoniae
What puts neonates at increased risk for perinatal bacterial meningitis?
—How can we reduce risk of perinatal transmission?
higher risk for premature infants, prolonged rupture of membranes, maternal fever at delivery
—screen pg women for Grp B Strep
Ethnicity with the highest rate of bacterial meningitis in the U.S.?
highest rates occur among Native Americans
Which is the anti-capsular bacteria antibody? (low yield?)
IgG2
Basic pathophy of bacterial meningitis?
- capsular bacteria colonize OR
introduced via trauma (e.g. basilar skull fx) OR
extension for sinus infx or brain abscess, etc. OR
presence of a CSF shunt - bacteremia (viral infx predisposes, IgG2 protects)
- Penetration of BBB (inflamm mediators IL1/TNF)
- These processes → cerebral edema & ↓ CBF
Gross and microscopic PATH changes?
GROSS
(1) acute purulent inflammatory exudate of leptomeninges (pia mater and arachnoid mater).
(2) subdural effusion (usually sterile).
(3) diffuse cerebral swelling, hydrocephalus.
MICROSCOPIC
(1) infiltration of leptomeninges with bacteria, polys
(2) pia mater resists bacterial penetration into brain parenchyma
(3) cerebral vasculitis including cortical venous thrombophlebitis and arteritis with aneurysmal or occlusive changes
Viral (“aseptic”) meningitis is usually caused by which genus of viruses?
Usually enteroviruses (Coxsackie B, Echovirus)
Pathogenesis of viral meningitis?
- Ingestion
- Pharyngeal/ileal Infx
- minor viremia
- systemic lymphatic involvement
- major viremia
- *sx onset**
- CNS/myocardium infx
Clinical Presentation of (any type of) meningitis in:
—Infants
—Older Children/Adults
—Geriatrics
- INFANTS less than a year of age the characteristic symptoms and signs of meningitis are difficult to elicit by history and exam. The most common symptoms are fever and irritability [20]. In practice, viral meningitis is often diagnosed during the clinical evaluation of febrile infants without an apparent source of fever.
- OLDER CHILDREN AND ADULTS meningitis presents with fever, headache, meningismus, nausea and vomiting [19]. Other signs of viral infection, i.e., rash, are present in a minority of cases.
- GERIATRIC PTS may present with only obtundation and mental status changes.
Physical Exam Findings of Meningitis
Kernig’s Sign - flex the knee and the hip (90°); extension of the leg from here causes back pain
Brudzinski’s Sign - passive flexion of neck (towards chest) causes involuntary flexion of both hips and knees
CSF results in bacterial meningitis?
—WBC
—Diff
—Glucose
(1) the CSF white cell count is usually > 200.
(2) the CSF WBC differential virtually always demonstrates a predominance of polys, typically > 90%.
(3) the CSF glucose is < 40 mg/dl and the CSF protein is increased over the normal values for age.
CSF results in viral meningitis?
—WBC
—Diff
—Glucose
(1) white cell count usu. 10 to 500 cells, but > 2000 have been reported. Virus occasionally isolated from the CSF of sx infants w/ nl CSF WBC counts
(2) WBC diff may initially demonstrate a predom of polys; invariably shifts to < 50% polys w/in 24 hours of onset (useful diagnostically)
(3) glucose: generally nl or slightly low
Acute complications of meningitis
(1) seizures
(2) SIADH
(3) hydrocephalus
(4) subdural effusion
(5) hearing loss
(6) hemiparesis, stroke
Causes of spirochetal meningitis
(1) syphilis
(2) leptospirosis
(3) Lyme disease
Tx for bacterial meningitis
1) Bactercidal abx: ceftriaxone + vanco (until cultures come back)
2) steroids
3) fluids
