EBV encephalitis

Magnetic
resonance imaging patterns of paediatric brain infections: a pictorial review based on the Western Australian experience. T2 hyperintensity in basal ganglia and/or thalami (Pattern 5). Case 1: 5-year-old child with afebrile generalised tonic–clonic seizures and CSF-proven EBV encephalitis. T2-weighted imaging (a) demonstrated bilateral hyperintensity of the basal ganglia, without abnormality on DWI (b). Case 2: 4-year-old child with fever, sore throat, irritability and CSF-proven EBV encephalitis. T2-weighted imaging (c, d) demonstrated bilateral hyperintensity of the basal ganglia and thalami (c), as well as scattered lesions in the cerebrum and brainstem (d). No DWI abnormality was present (not shown)
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Epstein-Barr virus (EBV) encephalitis is an uncommon manifestation of EBV infection and an uncommon causative organism of encephalitis in general.

Epidemiology

Most reported cases have been in children, although adults can rarely be affected .

Clinical presentation

Primary EBV infection is usually asymptomatic or manifests as infectious mononucleosis with fever, lymphadenopathy and tonsillopharyngitis . EBV encephalitis presents non-specifically with the following :

  • fever
  • headache
  • seizures
  • altered level of consciousness
  • symptoms of infectious mononucleosis usually being absent

The median time between the onset of prodromal features and neurological symptoms is 7 days . Other signs of EBV infection (e.g. myocarditis) may be present in some patients.

Pathology

Around 5% of viral encephalitis are due to EBV infection . Direct viral invasion and a secondary autoimmune response directed against the brain is thought to cause the symptoms and imaging findings . A variety of other neurological manifestations from EBV infection have also been described including myelitis, polyradiculitis, polyradiculomyelitis and acute cerebellar ataxia .

Radiographic features

MRI

In one study 71% of pediatric patients with EBV encephalitis had an abnormal MRI . The following is the typical pattern observed :

  • T2/FLAIR:
    • multifocal areas of hyperintensity
    • present mainly within the sub-cortical white matter and deep grey nuclei
  • DWI: high diffusion signal

Treatment and prognosis

Antivirals (e.g. acyclovir) are recommended . Symptomatic treatment of seizures and respiratory support may be needed. Although most patients survive lasting neurological deficit and death are not uncommon .