The median age of the patients was 24 (10-59) years and 3 were females. MRI was abnormal in all 6 patients. T2FLAIR hyperintensities were seen in bilateral thalami (double doughnut sign), pons and bilateral cerebellar hemispheres in 4 of the patients (Fig.1,2). All the patients showed restricted diffusion with 2patients showing peripheral post contrast enhancement. (Fig. 3, 5).

Dengue encephalitis typically involves basal ganglia and thalamus complex bilaterally, resulting in a characteristic ‘double doughnut’ appearance on brain MRI (Fig.4). ²The neuroradiological ‘double doughnut’ appearance may also be seen in other flavivirus encephalitis syndromes, such as Japanese encephalitis; however, in a given clinical setting the finding remains diagnostic because of the difficulty in performing lumbar puncture with severe thrombocytopaenia.

The involvement of pontine tracts gives rise to specific Jack-o-lantern sign ³ (Fig 10).In 4 patients, bilateral symmetrical white matter hyperintensities were also seen in the cortical grey and subcortical white matter. Tiny areas of blooming suggestive of haemorrhage was also noted in 3 of the patients (Fig.6).