Dengue encephalitis

Dengue encephalitis is a rare condition resulting from direct involvement of the central nervous system by the dengue virus, it is one of many viral encephalitides and flavivirus encephalitides.  

Epidemiology

Dengue infection and dengue encephalitis, predominately occurs in tropical and subtropical areas of the world 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

Dengue encephalitis typically involves the basal ganglia, thalami, cortical grey matter, and subcortical and deep white matter. Rarely, lesions are found in atypical locations such as the brainstem (particularly the substantia nigra), cerebellum, and hippocampus ¹.

CT

• hyperattenuating intraparenchymal foci representing spontaneous macrohaemorrhages ¹

MRI

• T2/FLAIR: hyperintense

• DWI/ADC: affected regions demonstrate restricted diffusion in most cases ¹

• SWI: microhemorrhages are commonly seen ¹

In the thalami, the rare double doughnut sign may be appreciated ³.

Differential diagnosis

• acute disseminated encephalomyelitis (ADEM)

  • hemorrhage 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 

  • ​hemorrhagic findings, although described, are less common ¹

• other flavivirus encephalitides

• herpes simplex encephalitis

  • usually spares the basal ganglia ¹