59 CNS Infections
Central nervous system (CNS) infections are among the most serious medical conditions affecting children, often leading to high morbidity and mortality if not promptly diagnosed and treated. They include infections that involve the brain (encephalitis), meninges (meningitis), or both (meningoencephalitis). In sub-Saharan Africa, including Ghana, CNS infections are common due to the high burden of bacterial, viral, parasitic, and fungal diseases. Understanding the pathophysiology, presentation, and management of these infections is crucial for all medical students and clinicians caring for children.
59.1 Introduction
CNS infections encompass a spectrum of conditions caused by microorganisms that invade the central nervous system, leading to inflammation of the brain, spinal cord, or their protective coverings. The major forms are:
- Meningitis: Inflammation of the meninges, often bacterial or viral.
- Encephalitis: Inflammation of the brain parenchyma, usually viral.
- Meningoencephalitis: Combination of both meningitis and encephalitis.
- Brain abscess: Localized collection of pus within the brain.
- Subdural or epidural empyema: Collection of pus between meningeal layers or between dura and skull.
These infections are medical emergencies. Early diagnosis and aggressive management can prevent death and long-term neurological sequelae such as hearing loss, seizures, and cognitive impairment.
59.2 Epidemiology
CNS infections occur worldwide but are particularly common in low-resource settings.
In Ghana and West Africa, they remain leading causes of hospitalization and death in children under five years.
- Bacterial meningitis is endemic in the “meningitis belt,” which includes northern Ghana, and outbreaks occur periodically.
- Viral infections, especially enteroviruses, herpes simplex virus (HSV), and arboviruses (e.g., West Nile virus), are also significant.
- Parasitic infections such as cerebral malaria remain a major cause of CNS involvement in endemic regions.
- Fungal infections (Cryptococcus neoformans, Candida species) occur primarily in immunocompromised children.
The burden of CNS infections in African countries is magnified by delayed presentation, limited access to diagnostic tools, and poor vaccination coverage.
59.3 Aetiology
59.3.1 Bacterial Causes
Common organisms vary by age:
- Neonates: Group B Streptococcus, Escherichia coli, Listeria monocytogenes.
- Infants and young children: Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae type b (Hib).
- Older children and adolescents: Neisseria meningitidis and Streptococcus pneumoniae.
59.3.3 3. Parasitic Causes
- Plasmodium falciparum (cerebral malaria)
- Toxoplasma gondii
- Trypanosoma brucei (African sleeping sickness)
59.3.4 4. Fungal Causes
- Cryptococcus neoformans
- Candida albicans
- Aspergillus species (rare)
59.4 Pathophysiology
The CNS is normally protected by the blood-brain barrier (BBB) and the meningeal layers. Infection occurs when microorganisms breach these defenses via:
- Hematogenous spread: The most common route, from systemic infection or nasopharyngeal colonization.
- Contiguous spread: From otitis media, sinusitis, or mastoiditis.
- Direct inoculation: From trauma, surgery, or congenital defects (e.g., spina bifida).
- Retrograde neuronal spread: seen with HSV and rabies.
Once pathogens enter the CNS:
- They trigger an inflammatory response involving cytokines, prostaglandins, and leukocyte infiltration.
- This causes cerebral edema, increased intracranial pressure (ICP), reduced cerebral perfusion, and neuronal injury.
- In meningitis, inflammation of the leptomeninges leads to disruption of CSF flow and hydrocephalus.
- In encephalitis, direct infection of neurons and glial cells causes necrosis and demyelination.
59.5 Clinical Features
The presentation depends on the child’s age and the specific infection but can be broadly grouped.
59.5.1 In Neonates
- Fever or hypothermia
- Poor feeding and lethargy
- Irritability, high-pitched cry
- Bulging fontanelle
- Seizures
- Apnea or cyanosis
59.5.2 In Older Infants and Children
- Fever, headache, vomiting
- Neck stiffness (meningism)
- Photophobia
- Altered level of consciousness
- Seizures
- Signs of raised intracranial pressure (ICP): papilledema, bradycardia, hypertension, and irregular respiration (Cushing’s triad)
- Focal neurological deficits (in encephalitis or abscess)
59.5.3 Specific Clues
- Petechial rash → Neisseria meningitidis infection.
- Paralysis, ataxia, movement disorders → viral encephalitis.
- Severe anemia and coma → cerebral malaria.
59.6 Differential Diagnosis
CNS infections must be differentiated from other causes of altered sensorium or seizures in children:
- Cerebral malaria
- Epilepsy or status epilepticus
- Febrile seizures
- Metabolic disorders (hypoglycemia, hyponatremia, uremia)
- Intracranial hemorrhage or tumor
- Toxic encephalopathy
59.7 Investigations
59.7.1 Laboratory Investigations
- Full blood count: Leukocytosis in bacterial infections; lymphocytosis in viral causes.
- Blood cultures: Identify causative bacteria in 30–50% of cases.
- Lumbar puncture (LP):
- Gold standard for meningitis diagnosis unless contraindicated (e.g., raised ICP, focal neurological signs).
- CSF findings:
- Bacterial meningitis: High protein, low glucose, turbid appearance, neutrophil predominance.
- Viral meningitis: Normal or mildly elevated protein, normal glucose, lymphocyte predominance.
- Fungal/TB meningitis: Elevated protein, low glucose, lymphocytes, positive India ink or acid-fast bacilli.
- CSF Gram stain and culture: Identifies specific bacteria.
- Polymerase chain reaction (PCR): Detects viral DNA/RNA (HSV, enteroviruses).
- Rapid antigen tests: Useful for Neisseria meningitidis, H. influenzae, and S. pneumoniae.
59.7.2 Neuroimaging
- CT or MRI brain before LP if raised ICP or focal signs are suspected.
- May reveal cerebral edema, abscess, or hydrocephalus.
59.7.3 Other Tests
- Blood glucose and electrolytes.
- Malaria smear or rapid diagnostic test (to exclude cerebral malaria).
- HIV screening in chronic or atypical infections.
59.8 Management
CNS infections constitute a medical emergency. Prompt empirical therapy, supportive care, and control of complications are vital.
59.8.1 1. Initial Stabilization
- Airway, breathing, and circulation support.
- Control seizures with intravenous diazepam or phenobarbital.
- Manage raised ICP: elevate head, restrict fluids, give mannitol if needed.
- Correct dehydration, hypoglycemia, and electrolyte imbalance.
59.8.2 2. Empirical Antimicrobial Therapy
Start antibiotics immediately after blood and CSF samples are collected (or sooner if LP delayed).
59.8.2.1 Empirical Antibiotic Regimens:
- Neonates: Ampicillin + Gentamicin or Cefotaxime (covering GBS, E. coli, Listeria).
- Infants and children: Ceftriaxone or Cefotaxime ± Vancomycin (for S. pneumoniae resistance).
- Suspected meningococcal infection: Add high-dose Penicillin G or continue ceftriaxone.
- TB meningitis: Standard anti-TB therapy (HRZE) with adjunctive corticosteroids.
- Fungal infections: Amphotericin B or Fluconazole.
- Cerebral malaria: Intravenous artesunate.
59.9 Supportive Care
- Antipyretics for fever.
- Fluid management: Maintain euvolemia; avoid fluid overload.
- Nutritional support: Enteral feeding as soon as tolerated.
- Seizure control: Maintain anticonvulsant therapy.
- Corticosteroids: Dexamethasone 0.15 mg/kg every 6 hours for 4 days in bacterial meningitis due to H. influenzae or S. pneumoniae (reduces hearing loss risk).
- Monitoring: Vital signs, neurological status, urine output, and electrolyte balance.
59.10 Complications
CNS infections can lead to devastating outcomes if not promptly managed.
Early complications: - Seizures and status epilepticus
- Cerebral edema and herniation
- Hydrocephalus
- Subdural effusion or empyema
- Shock and multi-organ failure
Late complications:
- Hearing impairment
- Developmental delay and learning difficulties
- Epilepsy
- Vision loss
- Motor deficits (paresis, ataxia)
- Behavioral and cognitive problems
59.11 Prevention
59.11.1 Immunization
Vaccination remains the most effective preventive measure:
- Haemophilus influenzae type b (Hib) vaccine, introduced into Ghana’s EPI, has drastically reduced cases.
- Pneumococcal conjugate vaccine (PCV13) protects against Streptococcus pneumoniae.
- Meningococcal vaccine useful during outbreaks in northern Ghana.
- Measles and mumps vaccines prevent postinfectious encephalitis.
59.11.2 Chemoprophylaxis
Close contacts of meningococcal meningitis cases should receive Rifampicin, Ciprofloxacin, or Ceftriaxone as prophylaxis.
59.11.3 Public Health Measures
- Early detection and treatment of ear and respiratory infections.
- Improved sanitation and reduced overcrowding.
- Health education and prompt healthcare-seeking behavior.
59.12 Prognosis
The prognosis of CNS infections depends on:
- The causative organism
- The age of the child
- Speed of diagnosis and initiation of treatment
- Availability of intensive care and rehabilitation
Mortality from bacterial meningitis in Africa remains between 15–30%. Survivors frequently suffer long-term sequelae, including hearing loss, epilepsy, and neurodevelopmental delays.
Viral meningitis usually has a good prognosis, while HSV encephalitis can cause permanent neurological impairment despite treatment. Cerebral malaria remains a leading cause of childhood neurological disability in endemic regions.
59.13 Conclusion
Central nervous system infections in children represent a critical emergency that demands prompt recognition and treatment. In Ghana and other tropical settings, bacterial meningitis, cerebral malaria, and viral encephalitis are the significant causes. Improved immunization coverage, early diagnosis, and effective antimicrobial therapy are essential to reduce mortality and prevent neurological sequelae. Strengthening laboratory capacity and surveillance systems will further enhance early detection and appropriate management.