The Spectrum of MRI Findings in Dengue Encephalitis

Abstract

Background In this study, we aimed to describe eight cases of dengue encephalitis along with their magnetic resonance imaging (MRI) findings. Dengue encephalitis is caused by an arbovirus that has four strains DENV1-DENV4. The dengue virus is usually non-neurotropic but DENV2 & DENV3 are neurotropic. Dengue encephalitis is characterized by headaches, seizures, and altered consciousness. Methodology At our facility, we performed 3T MRI on eight suspected cases of dengue encephalitis using the criteria established by Varatharaj et al. We were able to diagnose dengue encephalitis based on the proposed criteria which included symptoms, serology, cerebrospinal fluid (CSF) analysis results, MRI findings, and routine blood laboratory workup in dengue encephalitis. Because numerous brain regions are potentially impacted in severe cases of dengue encephalitis, an MRI of the brain can reveal the severity of the condition. In deteriorating situations, it may detect whether or not further regions are being impacted. Hence, MRI should be done in all suspected cases of dengue encephalitis. Results The changes observed on MRI of the eight cases were in the supra-tentorium (deep periventricular white matter, subcortical white matter, and deep gray matter of the brain, which includes basal ganglia and thalami), infra-tentorium (cerebellar white matter and brainstem, which includes pons), and occasionally in cortical gray matter. The MRI showed mild-to-moderate hyperintensities on T2-weighted images and fluid-attenuated inversion recovery sequence (FLAIR); diffusion restriction is seen on diffusion-weighted images. The neurological clinical features included non-localizing signs and symptoms such as altered mental status, headache with vomiting, and fever. Conclusions The commonly affected areas of the brain in dengue encephalitis are the basal ganglia, thalamus, brainstem, cerebellum, cortical white matter, periventricular white matter, and cortical gray matter, which are all hyperintense on T2-weighted images and FLAIR. The lesions are iso or hypointense on T1-weighted images and micro-hemorrhages appear as blooming on susceptibility-weighted MRI. MRI is a crucial initial investigation in suspected cases of dengue encephalitis and known cases of dengue fever experiencing worsening neurological conditions.

Keywords: 3-tesla mri; dengue fever/complications; expanded dengue syndrome; infectious encephalitis; mri findings.

Figure 1. Case 2: Asymmetrical hyperintensities are seen in the deep and subcortical white matter of the left parietal lobe on DWI axial (A) and T2W axial (B) images in a 28-year-old male with dengue encephalitis. An area of cerebellar hyperintensity is present in the T2W image (D). No diffusion restriction is seen in the FLAIR image (C).

T2W: T2-weighted image; DWI: diffusion-weighted image; FLAIR: fluid-attenuated inversion recovery sequence

Figure 2. Case 3: DWI and T2W images with diffusion restriction and axial hyperintensities, respectively, in both cerebral hemispheres and both caudate nuclei (black arrows in A & B, respectively), MRI of a 36-year-old male patient with dengue encephalitis.

DWI: diffusion-weighted image; T2W: T2-weighted image; MRI: magnetic resonance imaging

Figure 3. Case 4: Diffuse areas of diffusion restriction in DWI image are seen in both cerebral hemispheres including gray white matter, deep white matter, and basal ganglia region with sparing of the thalami and frontal white matter (A) in a 17-year-old male with dengue encephalitis. Corresponding hyperintensities are seen on T2W images (black arrows in B and C).

DWI: diffusion-weighted image; T2W: T2-weighted image

Figure 4. Case 5: Cortical areas of hyperintensities are observed in both parieto-occipital lobe on T2W (white arrows in B) and FLAIR images (white arrows in A and C) of a 40-year-old male patient on day one of presentation to the hospital.

T2W: T2-weighted image; FLAIR: fluid-attenuated inversion recovery sequence

Figure 5. Case 5: New interval increase in hyperintense areas in DWI and T2W images are identified in both parieto-occipital lobes and thalami of a 40-year-old male patient six days after presentation with dengue encephalitis (white arrows and black arrows, in A and B, respectively).

DWI: diffusion-weighted image; T2W: T2-weighted image

Figure 6. Case 5: Interval increase in the cortical hyperintensities are seen in both parieto-occipital lobe on DWI and FLAIR images (black arrows in A and B, respectively) of a 40-year-old male patient six days after presentation with dengue encephalitis.

DWI: diffusion-weighted image; FLAIR: fluid-attenuated inversion recovery sequence

Figure 7. Case 6: Diffuse gyral areas of diffusion restriction are seen in both cerebral hemispheres on DWI (white arrows in A and B), predominantly in the temporal lobe also involving both hippocampi on day one of presentation in a 15-year-old male patient with dengue encephalitis. Areas of diffusion restriction are also seen in both thalami on DWI with corresponding hyperintensities on T2W images (white short arrows in A, B, and C, respectively).

T2W: T2-weighted image; DWI: diffusion-weighted image

Figure 8. Case 6: MRI of a 15-year-old male patient on day six of admission. Increased gyral hyperintensities are observed in the posterior parietal lobe on T2W and DWI (white arrows in A, B, C).

T2W: T2-weighted image; DWI: diffusion-weighted image; MRI: magnetic resonance imaging

Figure 9. Case 8: Symmetrical hyperintensities are seen on FLAIR and T2W (white arrows in A and B, respectively) images in both thalami in a nine-year-old male patient on day one of presentation with dengue encephalitis. Central areas of blooming indicating hemorrhage are seen on SWI (C). Diffusion restriction is also seen on DWI (white arrow in D).

FLAIR: fluid-attenuated inversion recovery sequence; T2W: T2-weighted image; SWI: susceptibility-weighted image; DWI: diffusion-weighted image

Figure 10. Case 8: Diffusion restriction is also seen on DWI in the pons (white arrows in A). Areas of blooming are seen on SWI (white arrow in B). Hyperintense areas are seen in pons T2W sagittal images and FLAIR images (white arrow in C and D) in a nine-year-old male patient with dengue encephalitis.

DWI: diffusion-weighted image; SWI: susceptibility-weighted image; T2W: T2-weighted image; FLAIR: fluid-attenuated inversion recovery sequence