CNS Infections in Children

Central Nervous System (CNS) Infections in Children

• CNS infections are a notable cause of morbidity and mortality

• Identifying CNS infections is challenging due to nonspecific symptoms, especially in young infants

• Delayed or missed diagnoses can increase morbidity and mortality

• Conjugate vaccines have lowered the incidence of bacterial CNS infections

• Bacterial and viral infections remain significant contributors to CNS disease

• Patients with CNS infections often have similar clinical presentations

• The severity and constellation of signs depend on host-pathogen interactions and the affected CNS region

Common Symptoms and Signs of CNS Infection

• Common symptoms: headache, nausea, vomiting, anorexia, photophobia, restlessness, altered consciousness, irritability
• Common signs: fever, neck pain, nuchal rigidity, focal neurologic deficits, seizures, obtundation, coma

Meningitis vs. Encephalitis

• Meningitis: primary involvement of the meninges
• Encephalitis: indicates brain parenchymal involvement
• Anatomic boundaries may be indistinct, leading to clinical or imaging evidence of both meningeal and parenchymal involvement
• The term meningoencephalitis may better describe diffuse CNS infections, like those caused by viruses
• A brain abscess is a common example of a focal CNS infection

Diagnosing CNS Infections

• Diagnosis relies on a combination of factors:
  • Imaging of the brain
  • Testing cerebrospinal fluid (CSF) via culture, PCR, and serologic methods
  • Brain tissue biopsy in rare cases

Acute Bacterial Meningitis

• Bacterial meningitis is a serious pediatric infection associated with high rates of complications, long-term morbidity and mortality
• Antibiotics and vaccines have altered the disease spectrum

Common Causes of Bacterial Meningitis in Children Over 1 Month

• Haemophilus influenzae type b
• Streptococcus pneumoniae
• Neisseria meningitidis

Risk Factors for Bacterial Meningitis

• Lack of preexisting immunity to pathogens
• Higher meningitis incidence in young infants
• Recent colonization with pathogenic bacteria
• Close contact with individuals having invasive disease caused by N. Meningitidis or H. influenzae type b
• Crowding, poverty, male sex

Transmission of Meningitis Pathogens

• Through contact with respiratory tract secretions or droplets

Causes of Recurrent or Lethal Meningitis

• Defects in the complement system (C5-C8) are linked to recurrent meningococcal infection
• Defects in the properdin system increase the risk of lethal meningococcal disease
• Splenic dysfunction (sickle cell anemia) or asplenia increases the risk of pneumococcal, H. influenzae type b, and meningococcal infections
• T-lymphocyte defects (congenital, AIDS, chemotherapy, malignancy) increase the risk of Listeria monocytogenes CNS infections
• Congenital or acquired CSF leak across mucocutaneous barriers elevates the risk of pneumococcal meningitis
• A history of cochlear implants increases the risk of pneumococcal bacterial meningitis
• Lumbosacral dermal sinus and myelomeningocele are associated with staphylococcal, anaerobic, and gram-negative enteric bacterial meningitis
• CSF shunt infections increase the risk of meningitis caused by Pseudomonas aeruginosa and Staphylococcus species

Streptococcus pneumoniae Meningitis

• S. pneumoniae remains the most frequently identified bacterial pathogen in meningitis cases despite reduced incidence of pneumococcal meningitis

Risk Factors for Streptococcus pneumoniae Meningitis

• Anatomic or functional asplenia secondary to sickle cell disease
• HIV infection (20- to 100-fold higher infection rates in the first 5 years of life)
• Infections with endocarditis, otitis media, mastoiditis, sinusitis, pneumonia
• CSF otorrhea or rhinorrhea
• Presence of a cochlear implant
• Immunosuppression

Neisseria meningitidis

• Six serogroups (A, B, C, X, Y, and W-135) cause invasive disease in humans
• Meningococcal cases are more common in winter and spring due to associations with viral infections like influenza
• Nasopharyngeal carriage occurs in up to 15% of adults
• Infections in children often stem from daycare, colonized family members, or ill patients
• Colonization lasts weeks to months
• Children under 5 have the highest infection rates, with another peak between 15 and 24 years

Haemophilus influenzae type b

• Infections primarily occur in infants aged 2 months to 2 years, peaking at 6-9 months
• 50% of cases occur in the first year of life
• Household or daycare contacts of patients with H. influenzae type b disease are at higher risk
• Global vaccination has led to declines
• Those incompletely vaccinated, in underdeveloped countries, or with immune-compromising conditions remain at risk for H. influenzae type b meningitis
• Other serotypes of H. influenzae (a, f) have been linked to meningitis

Clinical Manifestations of Bacterial Meningitis

• Acute meningitis onset has two patterns:
  • Fever with upper respiratory tract or gastrointestinal symptoms followed by nonspecific CNS infection signs (lethargy, irritability)
  • Sudden shock, purpura, disseminated intravascular coagulation, reduced consciousness progressing to coma or death within 24 hours
• Signs and Symptoms:
  • Nonspecific Findings: fever, anorexia, poor feeding, headache, upper respiratory symptoms, myalgia, arthralgia, tachycardia, hypotension, cutaneous signs (petechiae, purpura, rash)
  • Meningeal Irritation: nuchal rigidity, back pain, Kernig sign, Brudzinski sign
  • Seizures: focal or generalized seizures (20–30% of patients); early seizures have little prognostic significance, persistent seizures indicate poorer prognosis
  • Altered Mental Status: irritability, lethargy, stupor, obtundation, coma (comatose patients have poor prognosis)
  • Additional Manifestations: photophobia, tache cerebrale

Signs of Increased Intracranial Pressure (ICP)

• Headache
• Emesis
• Bulging fontanelle or diastasis (widening) of the sutures
• Cranial nerve palsy (e.g., oculomotor, abducens)
• Hypertension with bradycardia, apnea, or hyperventilation
• Decorticate or decerebrate posturing
• Stupor, coma
• Papilledema (more common in complicated meningitis, chronic processes)

Important Notes

• Kernig and Brudzinski signs may be inconsistent in children under 12-18 months
• Focal neurologic signs usually indicate vascular occlusion
• Cranial neuropathies can result from focal inflammation -10–20% of children with bacterial meningitis have focal neurologic signs

Diagnosing Meningitis with Lumbar Puncture (LP)

• CSF for Gram stain and culture is the most important diagnostic step
• CSF testing includes: neutrophilic pleocytosis, elevated protein, reduced glucose concentrations

Contraindications for Lumbar Puncture (LP)

1. Evidence of increased ICP
2. Severe cardiopulmonary compromise
3. Infection of the skin overlying the LP site
4. Thrombocytopenia.

Lumbar Puncture Considerations

• Empiric antibiotic therapy should be initiated if LP is delayed
• Head CT scans before LP are not routinely recommended
• if Head CT scans are to be take, antimicrobial therapy should not be delayed

Additional Tests for Meningitis Diagnosis

• Blood cultures (80-90% sensitivity)
• C-reactive protein, erythrocyte sedimentation rate, and procalcitonin levels elevations

CSF Findings in Bacterial Meningitis

• CSF leukocyte count is elevated to >1,000/mm³, neutrophils predominate (75–95%)
• Turbid CSF is observed when the leukocyte count exceeds 200-400/mm³
• Healthy neonates may have more (up to to 20 leukocytes/mm³), but older children should have fewer

Differential Diagnosis for Bacterial Meningitis

• Tuberculosis, Syphilis
• Fungi, such as Candida, Cryptococcus, And Aspergillus
• Parasites, Such as Toxoplasma Gondii
• Viruses
• Focal infections; subdural empyema and spinal epidural abscess
• Noninfectious illnesses and autoimmune encephalitis
• Exposure to toxins