CASE 17239 Published on 02.04.2021

Flavivirus encephalitis presenting with cortical, thalami and posterior fossa lesions



Case Type

Clinical Cases


Cínthia Guedes Chaves1, Luciana Emery de Siqueira Pinto1, Pedro Neves Paiva de Castro1, Roberto Queiroz dos Santos1, Felipe da Rocha Schmidt2

1. Radiology department, Hospital das Américas.

2. Neurology department, Hospital das Américas.


35 years, male

Area of Interest Neuroradiology brain ; Imaging Technique MR
Clinical History

A 35-year-old male patient, presenting with ataxia, upper right limb spasms, and disorientation. Cerebrospinal fluid analysis indicated pleocytosis and increased protein levels.

Imaging Findings

Initially MRI showed hyperintensity on T2/FLAIR and restricted diffusion bilaterally in the perirolandic area, notably on the right, indicating cytotoxic oedema, which corresponds microscopically to intracellular oedema and cellular apoptosis.

Later the condition evolved the thalami, pons, middle cerebellar peduncle and cerebellum, also with T2/FLAIR hyperintensity and restricted diffusion.  

Post-Gadolinium FLAIR sequence demonstrated leptomeningeal enhancement on the right pre-central gyrus.

There was reduction of restricted diffusion after immunosuppressive treatment, with persistent T2/FLAIR hypersignal, indicating vasogenic oedema or gliosis.


Background and Clinical Perspective

The Flavivirus genus is responsible for worldwide distributed arboviruses, including West Nile, Yellow Fever and Dengue Fever.  These viruses are neurotropic and may manifest with meningitis, encephalitis, myelitis or radiculitis, after a febrile prodrome. Reduced level of consciousness, seizures, flaccid paralysis and parkinsonian movement disorders are some possible presentations [1].

Imaging Perspective

The MRI plays a critical role in the diagnosis, demonstrating T2/FLAIR change, although DWI may also present abnormalities [2]. Different imaging patterns have been described in the various Flavivirus infections, with basal ganglia involvement been a common presentation. Temporal lobe, hippocampus, white matter, pons, spinal cord and cranial nerves involvement may also occur [2,3]. Substantia nigra commitment have been suggested as a more specific pattern [4].

The final diagnosis is made by detection of IgM on cerebral spinal fluid or serum sample or detection of the virus RNA in PCR on the cerebral spinal fluid [1].

Therapy is based on managing complications. Symptoms and imaging abnormalities are often reversible [1, 4]. 


MRI abnormalities improved after immunosuppressive therapy with corticosteroids and cyclophosphamide. Patient presents preserved cognition and continuous spasticity, speech and motor abilities improvement.

Teaching Points

Flavivirus are neurotropic.

Basal ganglia and substantia nigra abnormalities may be a common presentation to different types of Flavivirus.

The cortex and cerebellum are not usually affected.


Written informed patient consent for publication has been obtained.

Differential Diagnosis List
Flavivirus encephalitis.
Toxic metabolic disorder.
Varicella encephalitis.
Epstein Barr infection.
Final Diagnosis
Flavivirus encephalitis.
Case information
DOI: 10.35100/eurorad/case.17239
ISSN: 1563-4086