Objective: To report a case of Japanese encephalitis (JE) presenting with thalamic–midbrain lesions followed by delayed parkinsonism confirmed by dopamine transporter imaging.

Background: JE is a mosquito-borne flavivirus infection that can cause severe encephalitis mainly endemic in Asia. Parkinsonism has been reported to occur either in the acute phase or as a delayed complication after infection; however, detailed clinical descriptions are limited. Herein, we report a case with a detailed clinical courses, including functional dopaminergic imaging response to treatment.

Method: We retrospectively analyzed the clinical course, laboratory data, imaging findings including brain magnetic resonance imaging (MRI), dopamine transporter (DAT) scan and cardiac 123I-meta-iodobenzyguanidine (MIBG) scintigraphylaboratory, and treatment response.

Results: A 72-year-old woman developed somnolence, fever followed by severe dizziness. The next day, she showed aphasia and left hemiparesis and was admitted to a local hospital. Brain MRI demonstrated hyperintensity extending from the right thalamus to the midbrain on fluid-attenuated inversion recovery (FLAIR) imaging. She was transferred to our hospital for further evaluation and management. The FilmArray panel was negative. Considering immune-mediated encephalitis, steroid pulse therapy with intravenous methylprednisolone (1,000 mg/day for 3 days, two courses) and blood purification therapy were initiated, resulting in improvement. Follow-up MRI demonstrated persistent thalamic–midbrain lesions and newly appearing bilateral cerebral white matter hyperintensities, particularly involving the substantia nigra. Imaging findings suggested flavivirus infection. Paired serum analysis showed elevated JE virus antibodies (HI 1:240, CF 1:32), which subsequently increased, confirming JE. Additional testing ruled out tick-borne encephalitis. Following rehabilitation, she regained independent ambulation but later developed parkinsonism. DAT scan demonstrated reduced dopamine transporter uptake in the bilateral striatum, right dominant, while cardiac 123I- MIBG scintigraphy was normal. L-dopa/ dopa decarboxylase inhibitor (DCI) therapy produced mild objective improvement.

Conclusion: We treated JE patients presenting with Parkinsonism. DAT scan findings may indirectly visualize parkinsonism caused by JEV. Additionally, L-dopa/DCI preparations may improve symptoms.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/delayed-parkinsonism-following-japanese-encephalitis-a-case-report-with-dopamine-transporter-imaging-and-l-dopa-dci-treatment/