¹⁸F-FDG PET/CT Metabolic Patterns in Clinically Probable Seronegative Autoimmune Encephalitis with Normal MRI Findings: A Retrospective Observational Study.

Authors

Priyanka Verma, Keerti Sitani, Shilpa Kulkarni, Swaleha Nadaf, Rahul Chakor, Sandip Basu

Published in

Journal of nuclear medicine technology. Oct 06, 2026. Epub Oct 06, 2026.

Abstract

Seronegative autoimmune encephalitis (AIE) poses a significant diagnostic challenge because of the absence of identifiable neuronal antibodies and frequently normal structural neuroimaging. ¹⁸F-FDG PET/CT has emerged as a sensitive functional imaging modality for detecting metabolic abnormalities in such patients. We conducted this study to evaluate the metabolic patterns observed on ¹⁸F-FDG PET/CT in patients with clinically suspected seronegative AIE and to assess the diagnostic utility of ¹⁸F-FDG PET/CT when MRI findings are normal. Methods: This retrospective observational study included 12 patients with clinically suspected AIE who tested negative for known neuronal antibodies and underwent ¹⁸F-FDG PET/CT. Clinical presentation, time to imaging, MRI findings, and PET metabolic patterns were analyzed. Results: Among the 12 patients evaluated (mean age, 23.08 y), seizures (83%), fever (42%), and behavioral changes (25%) were the most common presenting symptoms. Brain MRI findings were normal for all patients. ¹⁸F-FDG PET/CT revealed abnormal cerebral metabolism in all patients, with predominant basal ganglia hypermetabolism and characteristic anterior-to-posterior cortical metabolic gradient, found in 92% and 33% of patients, respectively. Medial temporal lobe hypermetabolism was observed in 25% of patients. The mean SUV_max in the basal ganglia was 12.28 (median, 18.72). Conclusion: ¹⁸F-FDG PET/CT demonstrated consistent and characteristic metabolic abnormalities among patients with seronegative AIE, even in the presence of normal MRI findings. However, these findings are not disease-specific and should be interpreted in conjunction with clinical and other diagnostic parameters. ¹⁸F-FDG PET/CT may serve as a valuable adjunctive diagnostic tool in clinically suspected seronegative AIE.

PMID:
42838617
Bibliographic data and abstract were imported from PubMed on 07 Oct 2026.

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