Neuro emergency. Do not delay antibiotics for LP — give empiric abx (and dexamethasone for ≥ 6 wk if H. flu or pneumococcal suspected) within 30 min, perform LP as soon as safe. Image (CT) before LP only if focal neuro deficit, papilledema, immunocompromised, or signs of ↑ICP.
🚩 Red-flag clues (must not miss)
- •Petechiae / purpura fulminans + fever = meningococcemia (mortality > 10%)
- •Bulging fontanelle, paradoxical irritability when held by caregiver = infant meningitis
- •Focal seizure or focal neuro deficit + fever = HSV encephalitis
- •Brudzinski / Kernig signs are insensitive in infants — absence does NOT exclude
History
- Fever, headache, photophobia, neck pain, lethargy, vomiting
- Vaccination status (Hib, PCV13, MenACWY/B)
- Sick contacts, recent abx (partially treated)
- Maternal HSV, neonatal exposures
Exam
- Vitals (Cushing triad late)
- Fontanelle, neck stiffness (poor sensitivity < 18 mo)
- Skin (petechiae below nipple line, purpura)
- Focal deficits, cranial nerves, fundoscopy
Labs
- CBC + diff, blood culture, BMP, glucose, coags, lactate, procalcitonin
- LP — opening pressure, cell count + diff, protein, glucose, gram stain, culture, HSV PCR, enterovirus PCR (consider meningitis/encephalitis panel)
Imaging
- Head CT (without contrast) BEFORE LP only if: focal deficit, papilledema, GCS ≤ 11, immunocompromised, recent seizure, age > 60 yr (not pediatric)
Differential & next step
| Diagnosis | Clue | Next step |
|---|---|---|
| Bacterial — Group B Strep (neonate) | — | Amp + cefotaxime/gent |
| Bacterial — E. coli (neonate) | — | Amp + cefotaxime |
| Bacterial — Listeria (neonate, < 1 mo) | — | Ampicillin (resistant to cephalosporins) |
| Bacterial — S. pneumoniae | — | Ceftriaxone + vancomycin + dexamethasone |
| Bacterial — N. meningitidis | — | Ceftriaxone; PEP for close contacts |
| Bacterial — H. influenzae type b | — | Ceftriaxone + dexamethasone (proven benefit) |
| Viral — HSV encephalitis | Focal seizure, temporal lobe finding | Acyclovir 20 mg/kg IV q8h; MRI brain (with & without contrast) |
| Viral — enterovirus (most common viral) | Summer/fall, mild course | Supportive |
| TB meningitis | Subacute, basilar enhancement, low CSF gluc | RIPE + steroids |
| Fungal (cryptococcal — immunocompromised) | HIV, CrAg+ | Amphotericin + flucytosine |
Medications & dosing
| Drug | Dose | Notes |
|---|---|---|
| Ceftriaxone (≥ 1 mo) | 100 mg/kg IV (max 4 g) loading, then 50 mg/kg q12h | |
| Vancomycin | 15 mg/kg IV q6h (target trough 15–20) | |
| Ampicillin (neonate / Listeria) | 100 mg/kg IV q6h | |
| Cefotaxime (neonate) | 50 mg/kg IV q6h | |
| Acyclovir (HSV) | 20 mg/kg IV q8h (neonate); 10–15 mg/kg q8h (older) | |
| Dexamethasone | 0.15 mg/kg IV q6h × 4 d | Give 10–20 min BEFORE or with first abx; benefit proven in H. flu and pneumococcal in children > 6 wk. Not for neonates. |
Management / next steps
- ABCs, isolate (droplet precautions until 24 h of effective abx)
- Empiric antibiotics within 30 min — do NOT delay for LP
- Dexamethasone with/before first dose (peds ≥ 6 wk)
- LP when stable; image first if indications above
- Admit PICU; chemoprophylaxis for close contacts (rifampin / cipro / ceftriaxone) if N. meningitidis or H. flu
CSF analysis — pediatric reference
Expected normal CSF by age 1,2
| Age | WBC (/µL) | Protein (mg/dL) | Glucose | Predominant cell |
|---|---|---|---|---|
| Term neonate (0–28 d) | ≤ 20 (some up to 22) | < 100 (up to 150) | ≥ 70% serum | Lymphocytes; up to 60% PMN can be normal |
| Infant (1–3 mo) | ≤ 9 | < 50 | ≥ 60% serum | Lymphocytes |
| Child (> 3 mo) & adult | ≤ 5 | < 45 | ≥ 60% serum (40–80 mg/dL) | Lymphocytes / monocytes |
Pattern by etiology 3,4
| Feature | Normal | Bacterial | Viral | TB / Fungal |
|---|---|---|---|---|
| Opening pressure (cm H₂O) | < 20 (older); < 28 (infant lateral) | ↑↑ (often > 30) | Normal–mildly ↑ | ↑↑ |
| Appearance | Clear | Cloudy / purulent | Clear | Clear / xanthochromic / fibrin web |
| WBC (cells/µL) | Neonate ≤ 20; child ≤ 5 | > 1000 (often) | 10–500 | 10–500 |
| Predominant cell | Lymph | PMN | Lymph (PMN early) | Lymph |
| Glucose (mg/dL) | ≥ 60% serum | ↓↓ (< 40% serum) | Normal | ↓ (< 40% serum) |
| Protein (mg/dL) | < 45 (child); < 100 (neonate) | ↑↑ (> 100) | Normal–mildly ↑ (< 100) | ↑↑ (often > 200) |
| Gram stain / culture | Negative | + in 60–90% pre-abx | Negative | AFB stain low yield; culture/PCR |
| Other tests | — | Lactate ↑; PCR panel | HSV PCR, enterovirus PCR | TB PCR, CrAg, India ink |
CSF Interpretation Widget
Enter age band and CSF values. Output is a pattern hint — always integrate clinically.
Normal CSF for age
- WBC and protein within normal limits for age (≤ 5 cells/µL, ≤ 45 mg/dL).
Next step: If clinical suspicion remains high, send PCR panel (HSV, enterovirus) and recheck in 12–24 h.
Traumatic Tap Correction
Subtract 1 WBC per ~700 RBC and ~1 mg/dL protein per 1000 RBC. Best applied when peripheral CBC is normal; correction is unreliable with anemia or peripheral leukocytosis.
Adjusted WBC
0 /µL
Adjusted protein
0 mg/dL
How to interpret
PMN (neutrophil) predominance 3,5
- Bacterial meningitis — typical pattern. Treat empirically while awaiting cx.
- Early viral meningitis (first 24–48 h) can show PMNs — recheck shifts to lymph.
- Parameningeal focus (brain abscess, epidural abscess) — image.
Lymphocytic predominance 3,5
- Viral (enterovirus, HSV — add PCR + acyclovir if any concern).
- TB / fungal — subacute course, very high protein, low glucose.
- Partially treated bacterial meningitis (recent antibiotics) — culture may be negative; treat empirically.
- Autoimmune (anti-NMDAR, ADEM) — consider if subacute encephalopathy.
Glucose & protein clues 3,4,6
- CSF glucose < 40% of serum = bacterial, TB, or fungal. Always draw paired serum glucose.
- Protein > 100 mg/dL in > 1 mo old = bacterial / TB / fungal until proven otherwise.
- Very high protein + low glucose + lymphs + basilar enhancement on MRI = TB meningitis.
- Traumatic tap correction: subtract ~1 WBC per 700 RBC; ~1 mg/dL protein per 1000 RBC.6
Pearl: in neonates, up to 20–22 WBC and protein up to 100–150 mg/dL can be normal — do not under-treat based on adult thresholds.1,2
Sources / footnotes
- Kestenbaum LA et al. Defining cerebrospinal fluid white blood cell count reference values in neonates and young infants. Pediatrics 2010;125(2):257–264.
- Nelson Textbook of Pediatrics, 21st ed. — neonatal CSF reference values (WBC ≤ 20–22, protein up to 100–150 mg/dL in term newborns).
- Tintinalli's Emergency Medicine, 9th ed. — meningitis chapter, CSF profiles by etiology.
- IDSA Practice Guidelines for the Management of Bacterial Meningitis (Tunkel AR et al., Clin Infect Dis 2004; updated 2017).
- AAP Red Book (current edition) — CSF cell predominance in viral vs bacterial meningitis.
- Mazor SS et al. Interpretation of traumatic lumbar punctures. Pediatrics 2003;111(3):525–528 — derivation of WBC/RBC and protein/RBC correction factors.
Clinical reference: fprmed Pediatric Meningitis
Pearls
- Antibiotics within 30 min; do NOT wait for LP.
- Steroids only proven helpful for H. flu and pneumococcal — give empirically before/with abx.
- Repeat LP in neonates with gram-negative meningitis to document sterility.
Source: https://fprmed.com/fprmedcom/Pages/Pedi/Pedi_Meningitis.html
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