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|Year : 2019 | Volume
| Issue : 5 | Page : 1360-1362
“Double Doughnut” Sign – Could it be a Diagnostic Marker for Dengue Encephalitis?
Chinky Chatur1, Ankit Balani2, Anjani Kumar3, Surendar Alwala3, Suresh Giragani2
1 Department of Radiology, Yashoda Hospital, Somajiguda, Hyderabad, India
2 Department of Neuroradiology and Interventional Radiology, Yashoda Hospital, Secunderabad, Telangana, India
3 Department of Radiology, Yashoda Hospital, Secunderabad, Telangana, India
|Date of Web Publication||19-Nov-2019|
Dr. Ankit Balani
61, Shyam Nagar, Pal Link Road, Jodhpur, Rajasthan
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Chatur C, Balani A, Kumar A, Alwala S, Giragani S. “Double Doughnut” Sign – Could it be a Diagnostic Marker for Dengue Encephalitis?. Neurol India 2019;67:1360-2
We read with a great deal of interest the article titled Dengue encephalitis: “Double doughnut” sign by Kumar et al. in the May–June 2017 issue of Neurology India, Volume 65, Issue 3. The article is well-written with self-explanatory images which provide insight into the findings of dengue encephalitis. We would like to make a pertinent contribution.
In their 22-year-old female patient, the authors made a diagnosis of dengue encephalitis based on the clinical, laboratory, and imaging findings. The authors coined the name “double doughnut” sign in reference to the imaging appearance of bilateral thalami on the magnetic resonance imaging (MRI) scan of the brain in the patient with dengue encephalitis. The center of the lesions showed intense diffusion restriction and the presence of hemorrhage on susceptibility weighted images.
Sir, we wish to share our experience with similar patients whom we encountered in the present monsoon season. A 13-year-old female child presented to a hospital with a history of generalized tonic-clonic seizure one hour prior to presentation. There was a history of headache with altered sensorium since three days and a high-grade fever since 8 days. Vital signs showed mild tachycardia, 101°F (38.33°C) fever, and normal blood pressure. She had post-ictal confusion; however, there were no focal neurological deficits. Hematology showed a blood glucose of 101 mg/dL and low platelet counts of 48,000/mm3. Serology was positive for NS1 antigen for dengue and the rapid malarial antigen test was negative. Cerebrospinal fluid (CSF) showed lymphocytic pleocytosis (>5/μL), elevated proteins (122 mg/dL), normal sugar (76 mg/dL), and IgG/IgM positive for dengue. IgM antibodies for leptospira and Japanese encephalitis were negative in the CSF. The MRI scan of the brain revealed. brain revealed T2, FLAIR hyperintensities in bilateral thalami which showed intense restriction of diffusion and blooming on the gradient sequence in the center of the lesions – the double doughnut sign [Figure 1]. T2, FLAIR hyperintense lesions were also noted in the bilateral cerebellar hemispheres which showed free diffusivity and no blooming on gradient sequences. Based on these findings, the diagnosis of dengue encephalitis was made and the patient was treated with supportive management including volume expanders, antipyretics, antivirals, and antiepileptics. The patient recovered well and was discharged in 7 days with no focal neurological deficits.
|Figure 1: Axial sections of contrast-enhanced MRI brain showing FLAIR (a) hyperintensity in bilateral thalami which show intense restriction of diffusion (b) with corresponding low ADC values (c) and blooming on gradient sequence (d) in center part of lesions giving “double doughnut sign” appearance. There is symmetrical T2 hyperintensity (e) in bilateral deep cerebellar white matter. There was no enhancement in postcontrast T1-weighted images (f)|
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Our second case was a 15-year-old-female child who presented with complaints of two episodes of vomiting followed by a loss of consciousness six hours prior to presentation. There was history of headache since 7 days and intermittent fever since 10 days. The patient was drowsy on initial examination and responsive to painful stimulus. Laboratory investigations revealed leukocytosis with blood count of 11,500/mm3 with serology positive for dengue (IgG/IgM). CSF showed lymphocytic pleocytosis with elevated proteins and normal sugar. IgM antibodies for dengue, leptospira, and Japanese encephalitis were negative. The MRI scan of the brain revealed symmetrical T2, FLAIR hyperintensities in the bilateral thalami and cerebellar hemispheres which showed an intense restriction of diffusion and blooming in the gradient sequence in the center ection of the lesions [Figure 2]. There was mild peripheral postcontrast enhancement and associated obstructive hydrocephalous with periventricular ooze. The patient responded to with a computer tomography (CT) scan performed 5 days later which showed interval reduction in hydrocephalus. The thalamic and cerebellar lesions appeared hypodense on the CT scan with no other parenchymal lesions.
|Figure 2: Axial sections of multi-echo contrast-enhanced MRI brain (a-h) showing FLAIR, T2 hyperintensity in bilateral thalami (a-d), and cerebellar hemispheres (e-h) which show intense restriction of diffusion with corresponding low ADC values and blooming on gradient sequence in center part of lesions giving “double doughnut sign” appearance. The lesions showed thin peripheral rim of enhancement (not shown)|
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Both our cases showed the “double doughnut sign” and symmetric involvement of bilateral cerebellar hemispheres. In the index case reported by Kumar et al., in addition to double doughnut sign, there were FLAIR hyperintensities in the brainstem and deep cerebellar white matter. Previously, Hegde et al. in their study reported imaging findings of eight patients with dengue encephalitis and concluded that all patients showed symmetric cerebellar involvement and presence of microbleeds/hemorrhage. In addition, MRI signal changes were noted in thalamus, gangliocapsular region, and medial temporal lobes in some patients. A similar case of dengue encephalitis was reported by Borawake et al. which showed bilateral thalamic and cerebellar involvement with a restriction of diffusion and blooming on gradient sequence.
MRI findings are less commonly described for dengue encephalitis.,,, Most of them report involvement of the bilateral thalamus, cerebellum, brainstem, gangliocapsular regions, and medial temporal lobes. Thus, in patients with doubtful serology and clinical manifestations, the imaging findings could help clinicians arrive at a definite diagnosis including bilateral thalamic involvement with the “double doughnut” sign and bilateral cerebellar involvement.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]