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What does the literature say about childhood encephalitis?

Recent studies show that the treatment of encephalitis in children is haphazard and improvements need to the made.  In general children with suspected encephalitis are previously healthy without any neurological conditions. Risk factors are immunosuppressed or travelled overseas. Because it is uncommon and the signs/symptoms are non-specific, initiating treatment is recommended even if there is no significant likelihood that they have the disease. 

The cause of encephalitis can be due to an infectious agent directly or indirectly by other inflammatory pathologies affecting the brain parenchyma. Herpes simplex virus type 1 is the most common cause of sporadic encephalitis.

Symptoms of encephalitis are non-specific, typically children will present with ‘flu-like’ symptoms (headache, nausea, vomiting and altered level of consciousness). Other complaints such as seizures and focal neurological signs are present. There is overlap with acute bacterial meningitis as they can have symptoms of fever, headache and neck stiffness. 

There are specific questions that must be asked by physician

  • Vaccination history
  • Travel history
  • History of a rash in child or contacts
  • Presence of cold sore or stomatitis may be caused by HSV 1

The absence of meningism should not be used to rule out encephalitis. 

Physicians should look for other symptoms such as raised blood pressure, papilloedema, abnormal pupil responses, abnormal flexion or extension to painful stimulus, altered breathing.

The failure to control the seizures is a risk factor for raised intracranial pressure, increased metabolic activity, acidosis and vasodilation

Early diagnosis is very important in order to treat the clinical syndrome and seek aetiology of the disease. Routinely it is advised to perform FBC, urea and electrolytes, liver function test, capillary glucose, blood gas, lactate, urinalysis and CSF.  

The best test to accurately determine encephalitis is autopsy or brain biopsy which is not practical. Surrogate markers include inflammatory cells in the spinal fluid or changes in brain imaging. CSF may be negative in the early stages of the disease. Neuroimaging is key in order to provide direct evidence of brain involvement from an infectious process or provide alternative diagnosis (space occupying legion, abscesses, vascular events etc). MRI is more sensitive. 

CT may misdiagnose HSV infection in the early stages of the condition whilst MRI will be able to detect other conditions (Kirkham 2012). 

Treatment is started with broad spectrum antimicrobials and antiviral medication while awaiting results of diagnostic studies.  Studies show that if therapy is commenced late, poor prognosis will ensue. So there should be a low threshold for starting acyclovir in suspected cases of encephalitis. 

However, there are also guidelines that suggests starting Aciclovir should not be commenced in children with known epilepsy with an increase in seizure and known febrile illness or acute head injury. 

Prognosis is generally poor for children with long-term neurological outcomes even despite appropriate therapy. Up to 67% of children will have long-term morbidity. 

In sum there are many unanswered questions about the ideal management and treatment of encephalitis due to lack of reporting, unknown aetiology in the majority of cases and few data on long-term outcomes.  The triage and appropriate treatment of children presenting with seizures, reduced level of consciousness or behavioural problems is complex and a controversial issue. 

References:

Thomson C, Knew R, Riodan A, Kelly D, Pollard AJ. Encephalitis in children. Archives of Disease in Childhood, 28 February 2012, Vol.97(2), p.150

Kirkham F. Guidelines for the management of encephalitis in children. Developmental Medicine & Child Neurology 2013, 55: 107–110