All children with suspected encephalitis should be investigated and treated in a hospital.
Signs of cerebral tissue damage, i.e. local neurological deficits or focal seizures, may be difficult to identify in a small infant.
A febrile and lethargic infant whose behaviour, according to the parents, has changed, should be referred to a hospital.
Symptoms
Diagnostic criteria consist of signs of parenchymal involvement.
Abnormal behaviour (irritability, fretfulness)
Lethargy
Problems with speech
Ataxia, cranial nerve paresis, limb paresis
Reduced level of consciousness
Seizures
Primary encephalitis
Signs and symptoms suggestive of an infection (fever, headache, tiredness) during the first few days
This is followed by signs of parenchymal involvement (see above).
Post-infectious or infection-related encephalitis (for example acute disseminated encephalomyelitis [ADEM], acute necrotizing encephalopathy [ANE])
History of a common infectious disease (upper respiratory tract infection or diarrhoea and vomiting) within the past few weeks
Slow or delayed recovery of the infectious disease and increased tiredness
Signs of parenchymal involvement (see above)
In ANE1 disease form a genetic predisposition to encephalitis triggered by a viral infection
Autoimmune encephalitis
Psychiatric symptoms, difficulty in sleeping, movement disorders and autonomic symptoms are significant in the clinical picture.
More common disease than assumed. In children, the typical form is the anti-NMDA receptor antibody-positive autoimmune encephalitis, which is associated with neurotransmission 2.
Investigations
Special testing for suspected diseases should also be taken into account in addition to the routine tests when examining the cerebrospinal fluid.
In suspected neuroborreliosis: antibodies and PCR testing, CXCL13 cytokine determination
In patients with known exposure to a tick/ticks: also serum TBE antibodies (tick-borne encephalitis)
In suspected autoimmune encephalitis: at least NMDA receptor antibodies; as necessary, on the basis of symptom picture more extensive determination of serum and cerebrospinal fluid autoimmune encephalitis antibodies
Treatment
Treatment should be initiated without delay in all patients with suspected encephalitis (unexplained central nervous system symptoms associated with an infection and/or EEG findings suggestive of encephalitis). The treatment must also cover herpes virus (intravenous acyclovir).
If bacterial meningitis / Borrelia meningoencephalitis cannot be excluded with a lumbar puncture, intravenous ceftriaxone should be added to the treatment. In some cases, a macrolide or doxycycline are to be considered.
In a young infant, the possible antimicrobial treatment commenced alongside acyclovir is chosen according to the age. The usual choice is either penicillin G or a combination of ampicillin and an aminoglycoside.
Less than one third of patients with encephalitis will sustain permanent neurological defects/damage.
Of every million children aged less than 16 years, 3.5 will die or sustain serious neurological damage as a result of encephalitis.
References
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Lancaster E, Martinez-Hernandez E, Dalmau J. Encephalitis and antibodies to synaptic and neuronal cell surface proteins. Neurology 2011;77(2):179-89. [PubMed]
Gable MS, Sheriff H, Dalmau J et al. The frequency of autoimmune N-methyl-D-aspartate receptor encephalitis surpasses that of individual viral etiologies in young individuals enrolled in the California Encephalitis Project. Clin Infect Dis 2012;54(7):899-904. [PubMed]
Neilson DE, Adams MD, Orr CM et al. Infection-triggered familial or recurrent cases of acute necrotizing encephalopathy caused by mutations in a component of the nuclear pore, RANBP2. Am J Hum Genet 2009;84(1):44-51. [PubMed]
Lönnqvist T, Isohanni P, Valanne L et al. Dominant encephalopathy mimicking mitochondrial disease. Neurology 2011;76(1):101-3. [PubMed]
Steffen R. Tick-borne encephalitis (TBE) in children in Europe: Epidemiology, clinical outcome and comparison of vaccination recommendations. Ticks Tick Borne Dis 2019;10(1):100-110. [PubMed]
Cellucci T, Van Mater H, Graus F, et al. Clinical approach to the diagnosis of autoimmune encephalitis in the pediatric patient. Neurol Neuroimmunol Neuroinflamm 2020;7(2). [PubMed]