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CC BY 4.0 · Arq Neuropsiquiatr 2022; 80(09): 975-976
DOI: 10.1055/s-0042-1755216
Images in Neurology

“Parenthesis sign” in Eastern equine encephalitis

“Sinal de parênteses” na encefalite equina do leste
María Belén Solís 
1   Pontificia Universidad Católica del Ecuador, Quito, Ecuador.
,
Ana Cristina Albuja 
2   Brown University, The Warren Alpert Medical School, Department of Pediatrics, Providence, United States.
3   Brown University, The Warren Alpert Medical School, Department of Neurology, Providence, United States.
,
Mauricio Fernando Villamar 
3   Brown University, The Warren Alpert Medical School, Department of Neurology, Providence, United States.
4   Kent Hospital, Department of Medicine, Warwick, United States.
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A 65-year-old man from the Northeastern United States presented in the summer with headaches, fever, and severe encephalopathy. Cerebrospinal fluid (CSF) demonstrated lymphocytic pleocytosis and hyperproteinorachia. Neuroimaging is shown in [Figures 1] and [2]. Serum and CSF showed positive immunoglobulin M (IgM) antibodies to Eastern equine encephalitis virus (EEEV).

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Figure 1 T2/fluid-attenuated inversion recovery (FLAIR) axial MRI shows bilateral, relatively symmetric hyperintensities within the basal ganglia, insulae, subcortical white matter, and thalami, as well as in the inferior right frontal lobe. Marked linear hyperintensities are present in the external capsules (arrows), and parts of the internal capsules (arrowheads) bilaterally. This finding, known as the “parenthesis sign”, may help differentiate between Eastern equine encephalitis and other encephalitides.
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Figure 2 T2/FLAIR hyperintensities extend into the mesial temporal lobes, midbrain, periaqueductal gray, and dorsal pons. Additionally, a dilated perivascular space is noted (asterisk).

EEEV is a mosquito-borne alphavirus. Although rare, it can cause severe arboviral encephalitis, with mortality >33%.[1] Magnetic resonance imaging features such as the “parenthesis sign” ([Figure 1]) can help distinguish between Eastern equine encephalitis and other encephalitides.[2] Although most publications on EEEV originate from North America, EEEV and other related alphaviruses also circulate in the Caribbean, Central America, and South America.[3] [4] [5]

Authors' Contributions

MBS: case concept and design, literature review, manuscript writing; ACA: interpretation of data, manuscript revision for intellectual content; MV: case concept and design, acquisition of data, figure editing, manuscript revision for intellectual content.




Publication History

Received: 06 February 2022

Accepted: 20 March 2022

Article published online:
04 October 2022

© 2022. Academia Brasileira de Neurologia. This is an open access article published by Thieme under the terms of the Creative Commons Attribution 4.0 International License, permitting copying and reproduction so long as the original work is given appropriate credit (https://creativecommons.org/licenses/by/4.0/)

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