Viral Encephalitis in Children
Viral encephalitis is a serious condition involving inflammation of the brain parenchyma. It’s a medical emergency requiring prompt diagnosis and treatment to prevent long-term neurological damage. It can occur alongside meningitis (meningoencephalitis).
Causes
A wide range of viruses can cause encephalitis, but some are more common in children.
Herpes Simplex Virus (HSV): This is the most common cause of sporadic, severe encephalitis in children. HSV-1 is the primary cause in older children, while HSV-2 is more common in neonates.
Enteroviruses: These are a frequent cause of viral meningitis but rarely lead to severe encephalitis.
Varicella Zoster Virus (VZV): This can cause encephalitis in both immunocompetent and immunocompromised children.
Other Viruses: Less common causes in the UK include Measles, Mumps, CMV, and arboviruses.
Clinical Presentation
The clinical presentation is characterised by signs of both meningitis and encephalitis.
Meningitis: Symptoms include fever, headache, neck stiffness, and photophobia.
Encephalitis: The key differentiating feature is the presence of neurological signs. These can include altered consciousness, seizures, focal neurological deficits, and behavioural changes.
Infants: In infants, symptoms are often non-specific and can include irritability, lethargy, poor feeding, and a bulging fontanelle.
Investigations
Prompt investigation is crucial, but it should not delay the start of empirical treatment.
Neuroimaging: An urgent MRI of the brain is the preferred imaging modality. In HSV encephalitis, this may show characteristic changes in the temporal lobes.
Lumbar Puncture (LP): An LP is essential for diagnosis. Cerebrospinal Fluid (CSF) analysis typically shows a lymphocytic pleocytosis, normal or slightly elevated protein, and normal glucose.
CSF PCR: CSF PCR for HSV-1, HSV-2, and Enterovirus is the gold standard for identifying the causative virus.
Other Tests: Bloods, including a full septic screen, are also performed to rule out a bacterial cause.
Management
Management should be initiated urgently, even before a definitive diagnosis is confirmed.
Empirical Therapy:
Start intravenous aciclovir immediately if HSV encephalitis is suspected. This can significantly reduce morbidity and mortality.
Start broad-spectrum antibiotics, such as ceftriaxone, until a bacterial cause is excluded.
Supportive Care: Children should be managed in a paediatric intensive care unit (PICU) for monitoring and management of seizures, raised intracranial pressure, and fluid balance.
Long-Term Management: Children who have recovered from viral encephalitis require long-term neurodevelopmental follow-up. They may also need anticonvulsant medication if they develop epilepsy.