CASE 17999 Published on 06.02.2023

Dengue Encephalitis in a young boy with seizure-MRI findings



Case Type

Clinical Cases


Shailendra Katwal1, Sundar Suwal2, Suman Lamichhane3, Abhisek Bajracharya4, Sunil Yadav4

1. Dadeldhura Subregional Hospital, Dadeldhura, Nepal

2. TUTH, Institute of Medicine, Kathmandu, Nepal

3. Nepal A.P.F. Hospital, Balambu, Kathmandu, Nepal

4. Nepal Medical College, Jorpati, Nepal


10 years, male

Area of Interest CNS, Neuroradiology brain ; Imaging Technique MR, MR-Diffusion/Perfusion
Clinical History

A 10-year-old boy presented with 10 days history of headache and high-grade fever.   Fever was associated with chills and rigor.  He developed abnormal body movement with generalized tonic-clonic seizures. The diagnosis of Dengue was confirmed by positive serology for IgM and NS-1 antigen.

Imaging Findings

With suspicion of dengue encephalitis, MRI was advised. MRI study showed multifocal lesions with T2/FLAIR high signal intensity in the cortex and subcortical region of the bilateral cerebral hemisphere, predominately involving the frontal lobes. Restricted diffusion with high signal in DWI and low signal in ADC is noted in the bilateral claustrum and external capsule as well as in the bilateral frontal subcortical white matter. A similar T2/FLAIR high signal is noted in the bilateral basal ganglia, right ventromedial thalamus, bilateral external capsule and claustrum. No blooming is seen in SWI images. A lumbar puncture was done to look for meningitis and was found to be normal.


Dengue is the arthropod-borne disease commonly seen in tropical countries caused by the bite of infected Aedes mosquitoes. Unplanned urbanization and international travel had led to increased distribution of dengue cases globally [1].   Although Nepal belongs to the endemicity category B for dengue as per the classification of WHO. There is an increasing trend of dengue cases in Nepal since 2004 [2]. CNS manifestations of the dengue virus are attributed to the Neurotropic effect, secondary to systemic involvement and post-infectious immune-mediated response [3].  Neurological manifestation of the dengue virus was first reported in 1976. Patients with neurological involvement may present with various symptoms. There may be a severe headache, altered sensorium, seizure, persistent fever, and neck rigidity. Dengue encephalopathy and encephalitis are different manifestations associated with the Dengue virus. Encephalopathy shows the diffuse involvement of brain parenchyma. Focal brain parenchymal abnormalities are associated with encephalitis which is due to direct invasion of the brain parenchyma with inflammatory changes [4].

MRI is a better imaging modality than CT for evaluating brain parenchyma involvement due to its better soft tissue resolution. Most commonly, there is the involvement of the cerebral cortex and subcortical white matter, basal ganglia, and thalami. Rare involvement of the cerebellar cortex and brain stem is also noted. These involved areas show hyperintensity in T2 weighted images with restriction of diffusion in DWI. Acute stroke pattern of involvement has also been explained in rare cases [5]. Small microhemorrhages areas showing blooming in MRI and hyperdensity in CT images have also been explained. Rare microhemorrhage was also noted in some cases. Dengue encephalitic features in association with hemorrhage are termed Dengue hemorrhagic encephalitis [6]. Association of Dengue encephalitis with PRES has been noted with hypodensity in the bilateral parieto-occipital region [7].

The main differential for consideration includes Acute disseminated encephalomyelitis [ADEM], Japanese encephalomyelitis [JE], and Herpes encephalitis[HE].  ADEM shows central nervous system manifestation after the resolution of the acute illness, while it occurs concurrently in dengue encephalitis. Findings of Dengue encephalitis are similar to JE and HE except for less incidence of haemorrhage in JE and no basal ganglia involvement in HE[8].

The prognosis of Dengue encephalopathy depends on the concomitant presence of hepatic dysfunction, coagulation disorder, electrolyte disbalance, and shock [10]. Imaging findings should be evaluated with clinical, serological, and epidemiological information to reach the correct diagnosis.

Differential Diagnosis List
Dengue Encephalitis
Acute disseminated encephalomyelitis
Japanese encephalitis
Herpes encephalitis
Final Diagnosis
Dengue Encephalitis
Case information
DOI: 10.35100/eurorad/case.17999
ISSN: 1563-4086