OIA1015 CNS MENINGITIS

Meningitis

Inflammation of the meninges surrounding the brain and spinal cord, often due to infection.

Common causes of meningitis

Viruses, bacteria, fungi, parasites, and non-infectious conditions (e.g., lupus, neoplastic spread).

Bacterial meningitis

Severe, rapidly progressive infection that can lead to death or neurological damage if untreated.

Non-infectious meningitis

Caused by cancer spread (neoplastic meningitis), lupus, or rupture of epidermoid/dermoid cysts.

Age-based pathogens

Newborns: Group B Streptococcus, E. coli

Adults: Streptococcus pneumoniae, Neisseria meningitidis

Risk-based pathogens

CSF shunt: Staphylococci

Cochlear implants: Streptococcus pneumoniae

AIDS: Tuberculosis meningitis

Neisseria meningitidis presentation

Petechial rash, typically non-blanching; may precede classic meningitis symptoms.

Kernig's sign

Pain or resistance when extending the knee with hip flexed at 90°.

Brudzinski's sign

Involuntary hip/knee flexion upon neck flexion.

Classic symptoms

Fever, headache, neck stiffness, vomiting, altered mental status.

Important signs

Fever, irritability, vomiting, elevated WBCs → suspect meningitis.

CSF findings suggestive of bacterial meningitis

Low glucose, high protein, high WBC with neutrophil predominance.

Opening pressure in meningitis

200 mm H₂O often indicates elevated intracranial pressure.

Correct CSF profile

1800 WBC/mm³, 95% neutrophils, glucose 25 mg/dL, protein 100 mg/dL = bacterial pattern.

Initial management

Start antibiotics immediately after cultures — delay only if lumbar puncture is contraindicated.

Empiric therapy selection

Based on age, immune status, and device presence (e.g., shunts, implants).

Dose optimization

High CNS doses needed due to blood-brain barrier (BBB) limitations.

Duration of therapy

Dependent on pathogen, clinical response, and host immunity.

Good CSF-penetrating antibiotics

Chloramphenicol, linezolid, fluoroquinolones, meropenem (with inflammation).

Poor CSF-penetrating antibiotics

Aminoglycosides, 1st/2nd gen cephalosporins, clindamycin.

Factors affecting CNS entry

Molecular weight, lipophilicity, protein binding, and meningeal inflammation.

Hydrophilic antibiotics

Need inflammation to cross BBB (e.g., beta-lactams).

When to use

For multidrug-resistant infections or poor IV response.

Drugs suited for this route

Polymyxins, vancomycin, aminoglycosides, daptomycin.

Avoid intrathecal β-lactams

Risk of seizures and neurotoxicity.

Volume & formulation constraints

Use preservative-free drugs; max 5–10 mL; pH and osmolality must match CSF.

Avoid preservatives

Toxic to CNS; must use preservative-free formulations.

pH/osmolality requirements

Solutions must be within 10% of physiologic CSF (pH ~7.3, osmolality ~281 mOsm/kg).

Neurotoxic risks

Includes aseptic meningitis, encephalopathy, seizures.

Rationale

Reduce inflammation and BBB permeability → limit neurological damage.

Effect on drug penetration

Decreases penetration of hydrophilic agents; minimal impact on lipophilic drugs like rifampin or quinolones.

Use in pediatrics

Dexamethasone reduces hearing loss in H. influenzae meningitis (>6 weeks old).

Use in adults

Reduces mortality in S. pneumoniae meningitis.

Dosing of dexamethasone

0.15 mg/kg IV every 6 hrs for 2–4 days; start 10–20 min before first antibiotic dose.

N. meningitidis or H. influenzae (Duration of therapy)

7 days

S. pneumoniae (Duration of Therapy)

10–14 days.

Gram-negative bacilli

21 days.

Listeria or TB meningitis

≥21 days; up to 12 months for TB.

Close contact prophylaxis

Rifampin, ciprofloxacin, or ceftriaxone for meningococcal exposure.

Vaccination roles

Pneumococcal, meningococcal, and Hib vaccines reduce incidence of bacterial meningitis.