05-6 Meningitis (Ch 25)

Question 1

meningitis definition vs. pyogenic meningitis

Answer 1

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

Question 2

Fungi that cause pyogenic meningitis

Answer 2

Histoplasma capsulatum
Coccidiodomyces immitus
Cryptococcus neoformans

Question 3

Amoeba that cause pyogenic meningitis

Answer 3

Naegleria sp.

Question 4

What categories of pathogens/procedures/maladies cause aseptic meningitis?

Answer 4

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.

Question 5

Bacteria that cause meningitis in 0-2 month olds?

Answer 5

group B streptococci
E. coli
Listeria monocytogenes

Question 6

Bacteria that cause meningitis in 2 month to 5 year olds?

Answer 6

Streptococcus pneumoniae
Neisseria meningitidis
Haemophilus influenzae (less common now w/ vaccination)

Question 7

Bacteria that cause meningitis in 5-60 year olds?

Answer 7

Streptococcus pneumoniae

Neisseria meningitidis

Question 8

Bacteria that cause meningitis in >60 year olds?

Answer 8

Streptococcus pneumoniae

Listeria monocytogenes

Question 9

Bacteria that cause meningitis in immunocompromised patients?

Answer 9

Listeria monocytogenes

Cryptococcus neoformans

Question 10

Bacteria that cause meningitis s/p basilar skull fx?

Answer 10

Streptococcus pneumoniae

Question 11

What puts neonates at increased risk for perinatal bacterial meningitis?
—How can we reduce risk of perinatal transmission?

Answer 11

higher risk for premature infants, prolonged rupture of membranes, maternal fever at delivery
—screen pg women for Grp B Strep

Question 12

Ethnicity with the highest rate of bacterial meningitis in the U.S.?

Answer 12

highest rates occur among Native Americans

Question 13

Which is the anti-capsular bacteria antibody? (low yield?)

Answer 13

IgG2

Question 14

Basic pathophy of bacterial meningitis?

Answer 14

1. 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
2. bacteremia (viral infx predisposes, IgG2 protects)
3. Penetration of BBB (inflamm mediators IL1/TNF)
4. These processes → cerebral edema & ↓‬‬ CBF

Question 15

Gross and microscopic PATH changes?

Answer 15

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

Question 16

Viral (“aseptic”) meningitis is usually caused by which genus of viruses?

Answer 16

Usually enteroviruses (Coxsackie B, Echovirus)

Question 17

Pathogenesis of viral meningitis?

Answer 17

1. Ingestion
2. Pharyngeal/ileal Infx
3. minor viremia
4. systemic lymphatic involvement
5. major viremia
   
   • *sx onset**
6. CNS/myocardium infx

Question 18

Clinical Presentation of (any type of) meningitis in:
—Infants
—Older Children/Adults
—Geriatrics

Answer 18

1. 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.
2. 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.
3. GERIATRIC PTS may present with only obtundation and mental status changes.

Question 19

Physical Exam Findings of Meningitis

Answer 19

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

Question 20

CSF results in bacterial meningitis?
—WBC
—Diff
—Glucose

Answer 20

(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.

Question 21

CSF results in viral meningitis?
—WBC
—Diff
—Glucose

Answer 21

(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

Question 22

Acute complications of meningitis

Answer 22

(1) seizures
(2) SIADH
(3) hydrocephalus
(4) subdural effusion
(5) hearing loss
(6) hemiparesis, stroke

Question 23

Causes of spirochetal meningitis

Answer 23

(1) syphilis
(2) leptospirosis
(3) Lyme disease

Question 24

Tx for bacterial meningitis

Answer 24

1) Bactercidal abx: ceftriaxone + vanco (until cultures come back)
2) steroids
3) fluids

Question 25

Management of viral meningitis

Answer 25

1. Admission to hospital
   a. Admission is not necessary for all cases. In general, indications for admission include:
   (1) infants under 6 months
   (2) cases with complicated neurological findings, i.e., seizures, obtundation
   (3) pts w/ any clinical or lab findings suggestive of bacterial dz
2. Management options
   a. Treat with appropriate systemic antibiotics until CSF and blood cultures are reported negative at 48-72
   hours.
   b. Observe without antibiotic therapy. This option generally requires a repeat lumbar puncture within 8-24 hours of the initial tap.
   c. When available, the enterovirus PCR assay may assist in immediate management decisions.
   d. The experimental anti-enterovirus drug pleconaril reduces the duration of headache and other symptoms
   by approximately 50% in adults [33].
3. Persistent or complicated cases
   a. Repeat lumbar puncture
   b. CSF AFB stain
   c. Culture CSF for bacteria, mycobacteria, fungi
   d. CSF and serum studies including: VDRL, cryptococcal antigen, leptospira antibody, Lyme disease anti- body