Approach to meningitis in children
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I now have a comprehensive Tintinalli table (Table 120-1) with age-based etiology and treatment. I have enough information to construct a thorough, well-organized answer. Let me compile this now.
Approach to Meningitis in Children
Meningitis is inflammation of the leptomeninges (the pia and arachnoid mater surrounding the brain and spinal cord). Untreated bacterial meningitis carries a mortality approaching 100%, so suspected cases require prompt, structured management.
1. Etiology by Age Group
The causative organisms shift dramatically with age - this governs empiric antibiotic choice.
| Age Group | Most Common Organisms | Notes |
|---|---|---|
| Neonates (0-28 days) | Group B Streptococcus (GBS), Escherichia coli, Listeria monocytogenes | HSV must also be considered; less common: S. pneumoniae, gram-negative bacilli |
| Young infants (28-90 days) | GBS, gram-negative bacilli, HSV (in exposed neonates) | S. pneumoniae and N. meningitidis become more likely toward 3 months |
| Older infants & children (>3 months) | Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae type b (Hib) | Hib nearly eliminated in vaccinated populations; pneumococcal vaccination (PCV7/PCV13) has markedly reduced disease |
| Adolescents | N. meningitidis (serogroups B, C, Y, W-135), S. pneumoniae | Meningococcal vaccine covers A, C, W-135, Y; MenB is a separate vaccine |
Tintinalli's Emergency Medicine, Chapter 120; Bradley and Daroff's Neurology in Clinical Practice, p. 1698
2. Clinical Features
Classic Triad (older children/adolescents)
- Fever
- Headache / photophobia
- Nuchal rigidity (meningismus)
These classic features are often absent or subtle in infants and neonates. Age-specific signs:
Neonates and Young Infants
Signs are non-specific and can be easily missed:
- Bulging fontanelle
- High-pitched cry, irritability, or paradoxical irritability (crying when held)
- Poor feeding, lethargy, decreased tone
- Temperature instability (hypothermia more common than fever)
- Apnea, seizures
- Guidelines universally recommend lumbar puncture as part of the evaluation of a neonate with any suspected infection.
Older Infants and Children
- Fever + altered mental status
- Vomiting, seizures
- Kernig's sign: patient supine, hip flexed to 90° - inability to extend knee past 135° (sensitivity <12%, but highly specific)
- Brudzinski's sign: passive neck flexion causes spontaneous hip/knee flexion (sensitivity <12%, but highly specific)
- Petechial or purpuric rash - strongly suggests meningococcemia (a medical emergency); typically on extremities but can occur anywhere
- Waterhouse-Friderichsen syndrome (bilateral adrenal hemorrhage) with DIC and purpura - rare but life-threatening complication of meningococcemia
Rosen's Emergency Medicine, p. 4164-4175
3. Investigations
Blood Tests
- CBC with differential - neutrophilia; neutropenia is a poor prognostic sign
- Blood cultures (before antibiotics if possible, but do NOT delay antibiotics to obtain)
- CRP, procalcitonin - procalcitonin <0.5 ng/mL has ~80% sensitivity, ~70% specificity for ruling out bacterial infection
- Blood glucose (for CSF:serum glucose ratio)
- Coagulation profile (DIC screen in sick patients)
- Serum electrolytes - hyponatremia common (SIADH from brain inflammation)
CT Head - When Required Before LP
Do NOT routinely CT before LP. CT is indicated if any of the following are present:
- Papilledema
- Focal neurologic deficits
- New-onset seizures
- Severely depressed or fluctuating level of consciousness
- Immunocompromised state
Lumbar Puncture - The Definitive Test
A CSF sample must be obtained from any child with signs of meningitis. Use the smallest spinal needle possible.
CSF Analysis - Interpretation:
| Parameter | Normal | Bacterial Meningitis | Viral Meningitis | TB Meningitis |
|---|---|---|---|---|
| Opening pressure | <20 cmH₂O | Elevated (20-50) | Normal/mildly elevated | Elevated |
| WBC | 0-5 (neonates up to 30) | >100-10,000, predominantly neutrophils | 10-500, predominantly lymphocytes | 10-500, lymphocytes |
| Protein | <45 mg/dL | Markedly elevated (100-500 mg/dL) | Normal to mildly elevated | Elevated |
| Glucose | ~60-80 mg/dL | Low (<40 mg/dL) | Normal | Low |
| CSF:serum glucose ratio | >0.6 | <0.3 (key finding) | >0.6 | <0.5 |
| Gram stain | Negative | Positive in ~80% (untreated) | Negative | Negative (AFB stain) |
Bradley and Daroff's Neurology in Clinical Practice, p. 1699; Frameworks for Internal Medicine
Additional CSF Tests:
- Gram stain and culture (gold standard)
- Meningitis/Encephalitis (ME) panel - multiplex PCR detecting 14 pathogens (6 bacterial, 7 viral, 1 fungal); rapid turnaround, useful in pretreated patients; does NOT replace culture (no antibiotic sensitivities)
- India ink + cryptococcal antigen (if immunocompromised)
- AFB smear and culture, ADA (if TB suspected)
- VDRL (if syphilis suspected in neonates)
Bacterial Meningitis Score (BMS) - Pediatric Tool
Used to distinguish bacterial from aseptic (viral) meningitis in children:
| Criterion | Points |
|---|---|
| Positive CSF Gram stain | 2 |
| CSF protein >80 mg/dL | 1 |
| Blood absolute neutrophil count ≥10,000 cells/mm³ | 1 |
| Seizure at or before presentation | 1 |
| CSF neutrophil count ≥1000 cells/mm³ | 1 |
- 0 points: Aseptic meningitis very likely
- 1 point: Aseptic meningitis less likely
- ≥2 points: Bacterial meningitis more likely
Tintinalli's Emergency Medicine, Chapter 120 (adapted from Nigrovic et al., PMID 19225382)
4. Management
Step 1: Stabilization (ABC)
- Airway, breathing, circulation
- IV access, fluid resuscitation for shock
- Treat hypoglycemia promptly (dextrose IV)
- Correct hyponatremia cautiously (if SIADH, restrict fluids to 75% maintenance after treating shock/dehydration)
- Seizure management: correct glucose and sodium before antiepileptics
Step 2: Empiric Antibiotic Therapy (Do NOT Delay)
Antibiotics must be given before LP results if the child is critically ill. Doses are higher than for other infections due to blood-brain barrier penetration requirements.
By Age Group:
| Age | First-line Empiric Therapy | Notes |
|---|---|---|
| Neonates (0-28 days) | Ampicillin 100 mg/kg Q8h (age <7d) or Q6h (>7d) + Gentamicin 4 mg/kg Q24h | Alternative: Ampicillin + Cefotaxime |
| Young infants (28-90 days) | Ampicillin 100 mg/kg Q6h + Gentamicin 2.5 mg/kg Q8h OR Cefotaxime 100 mg/kg Q8h | Add Acyclovir 20 mg/kg Q8h if HSV suspected |
| Older infants & children (>3 months) | Vancomycin + Ceftriaxone (or Cefotaxime) | Covers penicillin-/cephalosporin-resistant S. pneumoniae |
| All ages (Listeria risk) | Add Ampicillin to the above | Risk factors: immunocompromised, >50 years, diabetes, malignancy |
- For sinusitis/mastoiditis/otitis-associated meningitis: Add Metronidazole (for anaerobes)
- Penicillin-allergic (severe): Consult ID; consider Vancomycin + Meropenem or Rifampin
Antibiotic Doses for Meningitis (Children >1 month):
- Ceftriaxone: 100 mg/kg/day IV divided Q12h (max 4 g/day)
- Cefotaxime: 150-200 mg/kg/day IV divided Q8h (max 12 g/day)
- Vancomycin: 60 mg/kg/day IV divided Q6h (target AUC/MIC 400-600)
Red Book 2021 (AAP Committee on Infectious Diseases); Tintinalli's Emergency Medicine, Table 120-1
Step 3: Adjunctive Dexamethasone
- Dose: 0.15 mg/kg IV Q6h for 2-4 days
- Timing: Must be given before or with the first dose of antibiotics to be effective
- Benefit in children:
- Clearly reduces sensorineural hearing loss in H. influenzae type b meningitis
- Benefit in S. pneumoniae meningitis is controversial (AAP states "may be considered" but does not make a routine recommendation for children)
- No proven benefit for N. meningitidis meningitis
- Age threshold: infants ≥6 weeks and older
- Repeat LP after 48h if: clinical deterioration, no improvement, or dexamethasone was given (interferes with interpreting fever response)
Red Book 2021; Tintinalli's Emergency Medicine, Chapter 120
Step 4: Organism-Specific Definitive Therapy
Once culture and sensitivities are available:
| Organism | Preferred Treatment |
|---|---|
| S. pneumoniae (penicillin-susceptible) | Penicillin G or Amoxicillin alone; discontinue vancomycin |
| S. pneumoniae (penicillin non-susceptible, 3GC-susceptible) | Cefotaxime or Ceftriaxone alone; stop vancomycin |
| S. pneumoniae (resistant to both) | Vancomycin + Cefotaxime/Ceftriaxone ± Rifampin |
| N. meningitidis | Penicillin G or Ceftriaxone |
| H. influenzae type b | Ceftriaxone or Cefotaxime |
| HSV (neonatal/encephalitis) | Acyclovir 20 mg/kg Q8h x 14-21 days |
| M. tuberculosis | HRZE (Isoniazid + Rifampin + Pyrazinamide + Ethambutol) |
| Cryptococcus (immunocompromised) | Amphotericin B + Flucytosine |
Red Book 2021; Bradley and Daroff's Neurology
5. Complications and Prognosis
- Mortality with treatment: <10% (untreated: ~100%)
- Sensorineural hearing loss - most common sequela; more likely with S. pneumoniae and low CSF glucose
- Visual impairment
- Seizures (acute and post-meningitis epilepsy)
- Hydrocephalus (communicating or obstructive)
- Cognitive impairment, learning disabilities
- Subdural empyema / cerebral abscess
- Cerebral venous thrombosis (~1% of cases, presents with new seizures/focal deficits)
- Poor prognostic factors: coma, seizures, shock, respiratory distress, neutropenia, high CSF protein, fever lasting ≥7 days
Tintinalli's Emergency Medicine, Chapter 120
6. Prevention
- Hib vaccine: Has reduced H. influenzae meningitis by 55% and overall bacterial meningitis by 55%
- Pneumococcal conjugate vaccine (PCV13): Markedly reduced pneumococcal meningitis
- Meningococcal vaccines: Tetravalent (MenACWY) for serogroups A, C, W-135, Y; separate MenB vaccine required for serogroup B protection
- Chemoprophylaxis for close contacts of meningococcal disease: Rifampin, Ciprofloxacin, or Ceftriaxone
Quick Reference: Key Clinical Distinctions
| Feature | Bacterial | Viral | TB |
|---|---|---|---|
| Onset | Acute (hours) | Acute (hours-days) | Subacute (weeks-months) |
| CSF cells | Neutrophils | Lymphocytes | Lymphocytes |
| CSF glucose | Low | Normal | Low |
| CSF protein | High | Normal/mildly high | High |
| CSF:serum glucose | <0.3 | >0.6 | <0.5 |
| Treatment | Antibiotics + Dexa | Supportive (acyclovir for HSV) | HRZE + steroids |
Recent evidence note: A 2026 systematic review (PMID 41616789, Lancet Microbe) found significant antimicrobial resistance in meningitis caused by S. pneumoniae, N. meningitidis, and H. influenzae (2010-2024) - reinforcing the importance of vancomycin as part of initial empiric therapy for pneumococcal meningitis pending sensitivity results.
Primary sources: Tintinalli's Emergency Medicine, Chapter 120 (Meningitis in Infants and Children); Red Book 2021 (AAP); Bradley and Daroff's Neurology in Clinical Practice; Rosen's Emergency Medicine; Goodman & Gilman's Pharmacological Basis of Therapeutics
Why LDH CSF role
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I now have comprehensive, authoritative content from three major textbooks. Here is the full answer:
CSF LDH - Role in Meningitis
What is CSF LDH?
Lactate dehydrogenase (LDH, also written LD) is an intracellular enzyme present in virtually all tissues. In the CSF, it is released from damaged or lysed cells - neurons, glial cells, leukocytes, and meningeal cells. Because it does not normally cross the blood-brain barrier in significant amounts, a rise in CSF LDH indicates local cellular destruction within the CNS.
Normal CSF LDH values:
- Adults: ≤40 U/L
- Neonates: ≤70 U/L
Primary Role: Distinguishing Bacterial from Viral Meningitis
The single most useful application of CSF LDH is differentiating bacterial from aseptic (viral) meningitis:
- CSF LDH is significantly and consistently elevated in bacterial meningitis
- It remains near-normal in viral meningitis
- Using a cutoff of 40 U/L: sensitivity ~86%, specificity ~93%
- Overall sensitivity/specificity range: 70-85%, depending on cutoff used
This makes it a valuable adjunct when Gram stain is negative or results are pending.
Henry's Clinical Diagnosis and Management by Laboratory Methods
The Isoenzyme Pattern - Diagnostic and Prognostic Value
LDH has five isoenzymes (fractions 1-5), and the pattern in CSF is more informative than total LDH alone:
| LDH Fraction | Source | Finding in Bacterial Meningitis | Significance |
|---|---|---|---|
| LD4 + LD5 | Granulocytes (neutrophils) | Markedly elevated | Reflects the neutrophilic inflammatory response; predominant rise in uncomplicated bacterial meningitis |
| LD1 + LD2 | Brain tissue (neurons, glial cells) | Mildly elevated initially; rise sharply if neurologic damage occurs | Prognostic marker - sharp rise in LD1/LD2 predicts neurologic sequelae or death |
Key prognostic point: If LD1 and LD2 rise steeply, this signals direct parenchymal brain injury - these patients are at high risk for death or severe neurologic sequelae.
Adams and Victor's Principles of Neurology, 12th Ed., p. 713
Other Clinical Contexts Where CSF LDH is Elevated
CSF LDH is not specific to meningitis alone. Elevated levels are seen in:
| Condition | Mechanism |
|---|---|
| Bacterial meningitis | Neutrophil lysis + direct brain cell death |
| CNS leukemia / lymphoma | Tumor cell turnover and infiltration |
| Leptomeningeal metastases | Carcinoma of breast, lung, melanoma - LD5/total LD ratio >10-15% |
| Subarachnoid hemorrhage | RBC and brain cell lysis |
| Ischemic stroke | Neuronal death (mean LDH ~40.9 U/L in early stroke vs ~11.2 in controls) |
| Fungal meningitis (e.g., cryptococcal) | Cellular inflammation and damage |
| TB meningitis | Granulomatous inflammation |
Distinguishing traumatic tap from true intracranial hemorrhage: LDH is useful here - a traumatic tap with intact RBCs does NOT significantly elevate CSF LDH, whereas true intracranial hemorrhage (with cell lysis) does raise it.
Henry's Clinical Diagnosis and Management by Laboratory Methods, p. 122-124
CSF LDH vs. CSF Lactate - Important Distinction
These are related but different tests that are often confused:
| Parameter | Bacterial Meningitis | Viral Meningitis | Notes |
|---|---|---|---|
| CSF LDH | Elevated (>40 U/L) | Normal | Reflects cell lysis |
| CSF Lactate | Elevated (>35 mg/dL) | Normal | Reflects anaerobic metabolism (tissue hypoxia/ischemia) |
Both are elevated in bacterial and fungal meningitis but remain normal in viral meningitis. CSF lactate is often considered slightly more sensitive as a rapid discriminator.
Adams and Victor's Principles of Neurology
Why CSF LDH is Not Widely Used Routinely
Harrison's Principles of Internal Medicine (22nd Ed.) lists CSF LDH alongside CRP, lactic acid, neopterin, IL-1β, IL-6, β2-microglobulin, and TNF as potential discriminators between viral and bacterial meningitis - but notes that all of these "remain of uncertain sensitivity and specificity and are not widely used for diagnostic purposes."
The reasons CSF LDH has not replaced standard tests:
- Not specific - elevated in many CNS conditions (stroke, tumors, hemorrhage)
- PCR and multiplex panels (e.g., BioFire FilmArray ME panel) have largely superseded enzyme markers for rapid diagnosis
- CSF cell count, glucose, and protein are simpler, faster, and routinely available
- Gram stain and culture remain the gold standard
Summary: When CSF LDH is Clinically Useful
| Situation | How LDH Helps |
|---|---|
| Gram stain negative, etiology unclear | Supports bacterial over viral diagnosis if >40 U/L |
| Partially treated meningitis | Culture may be negative; LDH elevation persists |
| Prognostication | Sharp rise in LD1+LD2 fractions = high risk of neurologic damage or death |
| Traumatic tap vs. hemorrhage | LDH not elevated in traumatic tap |
| Suspected CNS malignancy | LD5/total LDH ratio >10-15% suggests leptomeningeal metastases |
| Pediatric seizure disorders | Distinct isoenzyme patterns in infantile spasms and febrile convulsions |
Sources: Adams and Victor's Principles of Neurology 12th Ed., p. 713; Henry's Clinical Diagnosis and Management by Laboratory Methods, p. 122-124; Harrison's Principles of Internal Medicine 22nd Ed., p. 1865-1868
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