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Table of Contents    
Year : 2018  |  Volume : 66  |  Issue : 2  |  Page : 578-580

Chikungunya encephalitis presenting as a brainstem syndrome and “boomerang” sign

Department of Neurology, SMS Medical College, Jaipur, Rajasthan, India

Date of Web Publication15-Mar-2018

Correspondence Address:
Dr. Ibraheem Khan
VPO-Samraya, Weir, Bharatpur, Rajasthan
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0028-3886.227269

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How to cite this article:
Jain RS, Khan I, Khandelwal K, Saini PK, Chaudhary R. Chikungunya encephalitis presenting as a brainstem syndrome and “boomerang” sign. Neurol India 2018;66:578-80

How to cite this URL:
Jain RS, Khan I, Khandelwal K, Saini PK, Chaudhary R. Chikungunya encephalitis presenting as a brainstem syndrome and “boomerang” sign. Neurol India [serial online] 2018 [cited 2020 Jun 4];66:578-80. Available from:

In modern imaging era, only a few case reports have shown diffusion restriction in adult patients with encephalopathy or encephalitis.[1]

Hence, we are reporting two cases of chikungunya encephalitis, one of them presented with postinfectious brainstem encephalitis; and, the second showed diffusion restriction in the posterior part of splenium (the boomerang sign).

Case 1

A 30-year old male patient presented with a 25-day history of fever and joint pains which subsided within 7 days on symptomatic treatment. After 15 days following the onset of fever, he developed slurring of speech, inability to close his right eye, deviation of his face towards the left side, decreased hearing on the right side, as well as ataxia of right-sided limbs and gait. The neurological examination revealed normal higher mental functions with cerebellar dysarthria. The cranial nerve examination revealed right-sided lower motor neuron facial weakness, and right sensorineural deafness with normal fundi and other cranial nerves. The motor system examination was normal. There was decreased sensation on the ipsilateral side of face and contralateral limbs. There were right-sided cerebellar signs with gait ataxia in the form of swaying towards the right side.

Magnetic resonance imaging (MRI) of the brain showed a lesion that was hypointense on T1-weighted images and hyperintense on T2-weighted images involving the lower pons including the middle cerebellar peduncle without contrast enhancement [Figure 1]a and [Figure 1]b. The work up for fever profile including peripheral smear and card test for malarial parasite, dengue immunoglobulin M (IgM) serology, blood cultures, and urine cultures were negative but chikungunya IgM serology was positive when assessed by the enzyme-linked immunosorbent assay (ELISA). The cerebrospinal fluid (CSF) examination was unremarkable except for the presence of oligoclonal bands. The diagnosis of chikungunya virus (CHIKV) brainstem encephalitis was made.
Figure 1: MRI brain showed (a) a well-defined, T2 hyperintense lesion, involving the lower pons including the middle cerebellar peduncle (b), without contrast enhancement

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Case 2

A 35-year old female patient presented with a 5-day history of fever, headache, and vomiting followed by altered sensorium, irrelevant talking and irritable behavior. The general physical examination and examination of other systems were unremarkable. The neurological examination revealed altered sensorium in the form of flexion response to painful stimuli. The motor system examination was unremarkable except for an extensor plantar response.

The MRI brain revealed diffusion restriction in the posterior splenial region and a correspondingly reduced apparent diffusion coefficient [ADC] (the boomerang sign) [Figure 2]a and [Figure 2]b. The CSF showed a cell count of 150 cells/mm 3 with 80% lymphocytes, normal sugar, and raised proteins (137 mg/dL). The CSF for Gram's stain, acid fast bacilli (AFB), India ink preparation, herpes simplex virus, West Nile virus, and tuberculous polymerase chain reaction (TB PCR) was negative. The visual evoked potential (VEP) showed a prolonged P100 peak latency in both eyes. The serum for IgM antibody against chikungunya was found to be positive. Hence, the diagnosis of chikungunya encephalitis was confirmed.
Figure 2: MRI brain revealed (a) diffusion restriction in the posterior splenial region; and, (b) corresponding reduced apparent diffusion coefficient level (the boomerang sign)

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Both patients were treated with high-dose intravenous methylprednisolone (1,000 mg/day for 5 days) and discharged in an improving condition.

The neurological complications of CHIKV occur during the infectious process or after a prolonged latent period of 15–20 days. The proposed mechanisms may be attributed to neurotropism of the virus to white matter tissue leading to intramyelinic edema due to inflammation and migration of inflammatory cells; cytokine-mediated immunologic reaction leading to microvascular endothelial injury; direct viral invasion of neurons; and, toxicity leading to post- or parainfectious demyelination.[2] Therefore, we are able to propose a mechanism that may be responsible for post- or parainfectious demyelination due to CHIKV in the presence of CSF oligoclonal bands, prolonged visual evoked potential (VEP) in both eyes, white matter lesions visible on MRI scans [Table 1], and a good response to steroids. Our case is also unique in being diagnosed as chikungunya based on the presence of the boomerang sign on imaging. CHIKV may be an infectious cause of demyelination. The clinicians should perform the chikungunya serology whenever an appropriate clinical setting is encountered.[3],[4],[5],[6],[7],[8]
Table 1: Characteristic radiological signs in viral encephalitis

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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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Ganesan K, Diwan A, Shankar SK, Desai SB, Sainani GS, Katrak SM. Chikungunya encephalomyeloradiculitis: Report of 2 cases with neuroimaging and 1 case with autopsy findings. AJNR Am J Neuroradiol 2008;29:1636-7.  Back to cited text no. 1
Gauri LA, Ranwa BL, Nagar K, Vyas A, Fatima Q. Post chikungunya brain stem encephalitis. J Assoc Physicians India 2012;60:68-70.  Back to cited text no. 2
Mathew T, Badachi S, Sarma GR, Nadig R. Boomerang sign” in rickettsial encephalitis. Neurol India 2014;62:336-8.  Back to cited text no. 3
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Yadav R, Ramdas M, Karthik N, Kulkarni GB, Dawn R, Kumar MV,et al. “Hot cross bun” sign in HIV-related progressive multifocal leukoencephalopathy. Neurol India 2011;59:293-4.  Back to cited text no. 6
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Das SK, Ray K. Wilson's disease: An update. Nat Clin Pract Neurol 2006;2013:482-93.  Back to cited text no. 8


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