Dengue encephalitis

Dengue encephalitis is a rare condition resulting from direct involvement of the central nervous system by the dengue virus.  

Epidemiology

Dengue infection, and thus dengue encephalitis, predominately occurs in tropical and subtropical areas. ¹ 

Clinical Presentation

Dengue encephalitis presents similar to other forms of encephalitis with non-specific symptoms such as headache, seizures and altered level of consciousness. 

Pathology

Dengue virus is a mosquito-transmitted RNA virus belonging to the Flavivirus genus.  There are four serotypes, designated DENV1-DENV-4. ¹ The serotypes most commonly implicated in neurologic manifestations of dengue virus infection are DENV2 and DENV-3. ²

Radiographic Features

CT

• hyperattenuating intraparenchymal foci representing spontaneous macrohaemorrhages ¹

MRI

• T2
  • hyperintense lesions involving the basal ganglia, thalami, cortical grey matter, and subcortical and deep white matter are the classical features of dengue encephalitis, usually with associated oedema
  • rarely, similar lesions are found in atypical locations such as the brainstem (particularly the substantia nigra), cerebellum, and hippocampus ¹
• DWI/ADC: affected regions demonstrate restricted diffusion in most cases ¹
• SWI: microhaemorrhages are commonly seen ¹

Differential Diagnosis

• acute disseminated encephalomyelitis (ADEM)
  • haemorrhage is uncommon ¹
  • the timing between the CNS manifestations and lesions and the febrile illness may assist in differentiating dengue encephalitis from ADEM - with dengue encephalitis manifesting during the febrile period and ADEM occurring after resolution of the acute illness ¹
• Japanese encephalitis 
  • ​haemorrhagic findings, although described, are less common ¹
• herpes simplex encephalitis
  • usually spares the basal ganglia ¹