✅ Model Answer:
• Diagnosis: Bacterial meningitis (likely S. pneumoniae or N. meningitidis) — fever, headache, vomiting, photophobia, nuchal rigidity. Elevated WBC (22,000) and CRP (18). CSF will show pleocytosis, low glucose, and high protein.
• Any other test: CSF analysis (cell count, glucose, protein, Gram stain, culture, PCR for S. pneumoniae, N. meningitidis, H. influenzae), blood culture, serum electrolytes, coagulation profile (DIC), CT head (if focal deficit or altered sensorium).
• What to do next: Start empiric IV antibiotics immediately (do NOT wait for LP results): ceftriaxone 50 mg/kg + vancomycin 15 mg/kg. Add dexamethasone 0.15 mg/kg/dose q6h for 2-4 days (before or with first antibiotic dose). Admit to PICU/ICU.
• Follow-up plan: Repeat LP at 48h if no improvement. Audiometry (hearing loss) before discharge. Neurodevelopmental follow-up. Vaccination review (PCV13, PPSV23, MenACWY, MenB, Hib). Prophylaxis for close contacts (rifampin for N. meningitidis).

✅ Model Answer:
• Neonates (0-28 days): GBS, E. coli, Listeria monocytogenes, HSV
• Infants 1-3 months: GBS, E. coli, S. pneumoniae, N. meningitidis, Listeria
• Children >3 months to 5 years: S. pneumoniae, N. meningitidis, H. influenzae type b (Hib) — now rare due to vaccination
• Children >5 years: S. pneumoniae, N. meningitidis
• Immunocompromised: S. pneumoniae, N. meningitidis, Listeria, Gram-negative bacilli, Cryptococcus, TB
• Vaccine-preventable: Hib (PCV13, Hib), N. meningitidis (MenACWY, MenB), S. pneumoniae (PCV13, PPSV23)

✅ Model Answer:
• CSF findings in bacterial meningitis:
- WBC: >100-1,000 cells/µL (neutrophil predominance >80%)
- Protein: >100-150 mg/dL (elevated)
- Glucose: <40 mg/dL or <40% of serum glucose (low)
- Gram stain: Positive in 60-80% (Gram-positive diplococci = S. pneumoniae; Gram-negative diplococci = N. meningitidis)
- Culture: Positive (gold standard)
- CSF opening pressure: Elevated (>20 cm H₂O)
- PCR: Highly sensitive for S. pneumoniae, N. meningitidis, H. influenzae
• Viral meningitis: Lymphocyte predominance, normal glucose, normal-mild protein elevation.
• TB meningitis: Lymphocyte predominance, low glucose, high protein, AFB smear/culture.

✅ Model Answer:
• Age 1-3 months:
- Ampicillin + cefotaxime (or gentamicin) + acyclovir (if HSV suspected)
• Age >3 months:
- Ceftriaxone (50 mg/kg/dose IV) + Vancomycin (15 mg/kg/dose IV)
- Ampicillin added if Listeria suspected (immunocompromised, age <3 months)
• If penicillin allergy: Chloramphenicol + vancomycin (or meropenem)
• Steroids:
- Dexamethasone: 0.15 mg/kg/dose q6h for 2-4 days (before or with first antibiotic dose) — reduces neurologic sequelae in pneumococcal meningitis.
• Duration:
- S. pneumoniae: 10-14 days
- N. meningitidis: 7-10 days
- H. influenzae: 7-10 days
- Listeria: 21 days
- Gram-negative: 21-28 days

✅ Model Answer:
• Indication: Suspected or confirmed pneumococcal meningitis (S. pneumoniae).
• Mechanism: Reduces inflammation-mediated damage by downregulating inflammatory cytokines (TNF-α, IL-1) and decreasing cerebral edema, intracranial pressure, and neurologic sequelae.
• Benefit:
- Reduces risk of hearing loss (most important)
- Reduces neurologic sequelae (cognitive impairment, motor deficits)
- May improve survival in severe cases
• Dosing: 0.15 mg/kg/dose IV q6h for 2-4 days (maximum 4 days).
• Timing: Give before or with the first dose of antibiotics (or within 30 minutes after).
• Not indicated: For meningococcal meningitis (no proven benefit) or viral meningitis.

✅ Model Answer:
• Complications:
- Neurologic: Hearing loss (most common complication, especially S. pneumoniae), seizures, hydrocephalus, subdural effusions/empyema, brain abscess, ventriculitis, cerebral palsy, cognitive impairment, learning difficulties
- Systemic: Sepsis, septic shock, disseminated intravascular coagulation (DIC), water intoxication (SIADH), adrenal insufficiency (Waterhouse-Friderichsen syndrome in meningococcal sepsis)
- Cranial nerve palsies: CN VI (abducens), CN VII (facial), CN VIII (auditory)
- Hearing loss: Sensorineural hearing loss (SNHL) — requires audiology follow-up
- Mortality: 5-15% in children (higher in infants, neonates, and immunocompromised)

✅ Model Answer:
• Indications for CT/MRI:
- Before LP: If focal neurologic deficits, papilledema, altered sensorium, or immunocompromised (risk of herniation)
- After LP: If not improving after 48-72 hours of antibiotics (persistent fever, worsening neurologic status)
- Suspected complications: Subdural effusion/empyema, brain abscess, hydrocephalus, ventriculitis
- Focal deficits or seizures
- Immunocompromised patients
• CT/MRI findings:
- Meningeal enhancement: Leptomeningeal enhancement (contrast)
- Hydrocephalus: Dilated ventricles (communicating or non-communicating)
- Subdural effusion/empyema: Fluid collection with enhancement
- Brain abscess: Ring-enhancing lesion
- Cerebral edema: Sulcal effacement, diffuse edema
- Venous thrombosis: Cortical vein thrombosis

✅ Model Answer:
• Prognosis:
- Good: If treated promptly and appropriately (mortality <5-10%)
- N. meningitidis: Better prognosis than S. pneumoniae
- S. pneumoniae: Higher risk of neurologic sequelae (hearing loss, cognitive impairment)
- H. influenzae: Good prognosis with vaccination
- Age: Infants and neonates have worse outcomes
- Mortality: 5-15% (higher in developing countries)
• Long-term follow-up:
- Audiology: Comprehensive hearing evaluation (OAE, ABR) before discharge and at 6 months (risk of SNHL)
- Neurology: Monitoring for seizures, developmental milestones, motor function
- Developmental pediatrics: Regular assessments of cognitive, language, motor, and social-emotional development
- Neuroimaging: Repeat MRI/CT if complications (hydrocephalus, abscess)
- Vaccination: Ensure age-appropriate immunizations (PCV13, Hib, MenACWY, MenB)
- Prophylaxis: For close contacts (rifampin for N. meningitidis)
- Family support: Counseling, early intervention services if needed