Case report of anti-vimentin IgG-associated autoimmune encephalitis: diagnostic challenges and the role of 18F-DPA714 PET/MRI.

Abstract

Background: Anti-vimentin IgG-associated autoimmune encephalitis (AE) is a recently described autoimmune astrocytopathy characterised by relapsing-remitting cerebellar ataxia, brainstem involvement and pyramidal tract lesions. Nevertheless, several key aspects remain poorly elucidated, including the full clinical phenotypic spectrum (particularly peripheral nervous system (PNS) involvement), the interpretation of serological discrepancies and long-term management outcomes. Additionally, the imaging evidence for neuroinflammation and the evidence regarding evolution following treatment remain insufficient.

Case presentation: We reported a man in his late 40s who developed a core triad of cerebellar ataxia, pyramidal signs and peripheral neuropathy. Conventional MRI was unremarkable, but cerebrospinal fluid analysis revealed anti-vimentin IgG positivity (titre 1:10) with type III oligoclonal bands while serum was negative. ¹⁸F-DPA714 positron emission tomography/MRI showed elevated tracer uptake in the mesial temporal lobe, frontal lobe and brainstem, correlating with clinical signs. After intravenous immunoglobulin induction and ofatumumab maintenance therapy, the patient showed clinical improvement (modified Rankin Scale from 2 to 1) at 3-month follow-up, paralleled by reduced tracer uptake.

Conclusions: This first reported middle-aged male case expands the demographic and phenotypic spectrum of anti-vimentin IgG-associated AE to include PNS involvement. This case highlights the diagnostic value of antibody detection and advanced imaging modalities in atypical presentations of anti-vimentin IgG-associated AE.