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Year : 2018  |  Volume : 64  |  Issue : 2  |  Page : 127

Dengue doughnut: A diagnostic magnetic resonance imaging finding in dengue encephalitis

1 Department of Imaging and Interventional Radiology, Kerala Institute of Medical Sciences, Trivandrum, Kerala, India
2 Department of Radiology, DDNMRC, Kerala Institute of Medical Sciences, Trivandrum, Kerala, India

Date of Web Publication23-Apr-2018

Correspondence Address:
N Shah
Department of Imaging and Interventional Radiology, Kerala Institute of Medical Sciences, Trivandrum, Kerala
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jpgm.JPGM_374_17

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How to cite this article:
Shah N, Nair A V, Ahamed S, Manoj K S. Dengue doughnut: A diagnostic magnetic resonance imaging finding in dengue encephalitis. J Postgrad Med 2018;64:127

How to cite this URL:
Shah N, Nair A V, Ahamed S, Manoj K S. Dengue doughnut: A diagnostic magnetic resonance imaging finding in dengue encephalitis. J Postgrad Med [serial online] 2018 [cited 2023 Sep 27];64:127. Available from:

We came across a case of 23-year-old woman with clinical and biochemical parameters [Dengue NS1, dengue immunoglobulin G (IgG) and IgM were positive, cerebrospinal fluid (CSF) analysis was positive for IgM dengue antibodies] suggestive of dengue fever. Magnetic resonance imaging (MRI) brain was done in view of headache, diplopia, and ataxia.

MRI with contrast [Figure 1] revealed T2/FLAIR hyperintense signals in bilateral thalami, bilateral cerebellar hemispheres, and vermis. Centre of bilateral thalami showed diffusion restriction and blooming in susceptibility weighted imaging (SWI) characteristic of “double doughnut sign” due to petechial hemorrhages.[1],[2] Postcontrast T1 fat sat images revealed rim enhancement in thalamus surrounding the area of diffusion restriction/susceptibility artifact. The appearance in postcontrast images is an inverse of diffusion weighted imaging. So we coined the term “Inverted double doughnut sign” to describe the finding. Patient was managed conservatively with supportive treatment. Her symptoms improved during the course of hospital stay and was discharged. On follow-up after 6 weeks she was clinically unremarkable, with MRI brain showing persistence of double doughnut sign.
Figure 1: Contrast-enhanced MRI showing (a and b) FLAIR hyperintense signals involving bilateral thalami, bilateral cerebellar hemispheres, and vermis; (c) SWI sequence showing blooming in central aspect of thalamus bilaterally with (d) diffusion restriction at the site of blooming; (e) postcontrast T1 fat sat images showing rim enhancement surrounding the area of diffusion restriction; (f) MR venogram showing normal superficial and deep dural sinus

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Although diagnosis of dengue encephalitis is mainly based on clinical and laboratory investigations, MRI has a supportive role in confirming a diagnosis of dengue neurotropism. Japanese encephalitis is considered the close differential in MRI when there is thalamic and basal ganglia involvement, with similar imaging manifestations. In such cases, a CSF study would be contributory. There is no specific targeted treatment for dengue encephalitis. Supportive management is the mainstay. Studies have shown inhibition of viral replication in cell culture by agents such as geneticin and ribavirin.[3]

“Dengue double doughnut sign” on diffuse weighted imaging and the “inverted dengue double doughnut sign” on postcontrast T1 fat sat sequences is unique for dengue encephalitis involving thalamus and can be considered as a diagnostic feature if the case falls clinically into accepted criteria for dengue encephalitis.

Declaration of patient consent

The authors certify that appropriate patient consent was obtained.

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Conflicts of interest

There are no conflicts of interest.

 :: References Top

Kumar AS, Mehta S, Singh P, Lal V. Dengue encephalitis: “Double doughnut” sign. Neurol India 2017;65:670-1.  Back to cited text no. 1
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Soni BK, Das DSR, George RA, Aggarwal R, Sivasankar R. MRI features in dengue encephalitis: A case series in South Indian tertiary care hospital. Indian J Radiol Imaging 2017;27:125-7.  Back to cited text no. 2
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De Clercq E. Yet another ten stories on antiviral drug discovery (Part D): Paradigms, paradoxes and paraductions. Med Res Rev 2010;30:667-707.  Back to cited text no. 3


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