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Imaging CD19+ B Cells in an Experimental Autoimmune Encephalomyelitis Mouse Model using Positron Emission Tomography
Published on: January 20, 2023
Distinguishing autoimmune encephalitis from its mimics using brain [¹⁸F]-FDG PET: real-world study
Hélène Rostand1, Fiene Marie Kuijper1, Cristina Birzu2
1Department of Nuclear Medicine, Pitié-Salpêtrière Hospital, AP-HP, Sorbonne Université, Paris, France.
Background:
Diagnosing autoimmune encephalitis (AE) remains challenging due to heterogeneous clinical presentations, frequent seronegativity, and limited MRI sensitivity. We evaluated the diagnostic performance of brain [¹⁸F]-FDG PET/CT in a real-world cohort of patients with suspected AE.
Methods:
Consecutive patients referred for [¹⁸F]-FDG PET/CT for suspected AE between January 2020 and July 2023 were retrospectively included. Final diagnoses were established using international criteria, expert consensus, and follow-up. PET findings were assessed visually, with voxel-wise and regional analyses, compared with 54 healthy controls, and stratified by age and treatment.
Results:
Among 141 patients (48 ± 21 years), 33% had AE, 43% differential diagnoses (DD), and 24% remained undetermined. Of AE cases, 70% were definite, 63% seropositive, and 35% had supportive MRI findings. AE showed cortical hypometabolism with mesiotemporal lobe (MTL), basal ganglia, cerebellum, midbrain, and insula hypermetabolism (p < 0.05). Compared with DD, AE exhibited lower occipital/prefrontal and higher MTL, insular, and midbrain metabolism (p < 0.001), with good discrimination versus DD (AUC 0.82-0.83). MTL hypermetabolism, alone or with cortical hypometabolism, emerged as the most specific feature, whereas other regional metrics and ratios were less reliable (AUC ≤ 0.73). Accuracy of visual PET analysis was high in patients under 40 years (positive/negative predictive values 82%/81%) and declined with age to 81%/69% at 40-65 years and 79%/64% over 65 years.
Conclusions:
[¹⁸F]-FDG PET/CT identifies a characteristic metabolic signature of AE and differentiates it from relevant mimics, supporting its role as a complementary diagnostic biomarker, particularly in younger patients.
Insights
Brain [¹⁸F]-FDG PET/CT shows a distinct metabolic pattern in autoimmune encephalitis (AE), aiding diagnosis. This imaging technique helps differentiate AE from other conditions, especially in younger individuals.
Area of Science:
- Neuroimaging
- Nuclear Medicine
- Neurology
Background:
- Diagnosing autoimmune encephalitis (AE) is challenging due to varied symptoms, seronegativity, and low MRI sensitivity.
- Brain [¹⁸F]-FDG PET/CT is evaluated as a diagnostic tool for suspected AE in a real-world clinical setting.
Purpose of the Study:
- To assess the diagnostic performance of brain [¹⁸F]-FDG PET/CT in patients with suspected autoimmune encephalitis.
- To identify characteristic metabolic patterns of AE using [¹⁸F]-FDG PET/CT and differentiate it from mimics.
Main Methods:
- Retrospective analysis of 141 patients undergoing [¹⁸F]-FDG PET/CT for suspected AE.
- Final diagnoses established using international criteria and expert consensus.
- PET findings analyzed visually and quantitatively, compared with healthy controls, and stratified by age.
Main Results:
- Autoimmune encephalitis (AE) cases (33%) exhibited cortical hypometabolism and mesiotemporal lobe (MTL), basal ganglia, cerebellum, midbrain, and insula hypermetabolism.
- [¹⁸F]-FDG PET/CT effectively discriminated AE from differential diagnoses (AUC 0.82-0.83), with MTL hypermetabolism being a key feature.
- Diagnostic accuracy was highest in patients under 40, with positive/negative predictive values of 82%/81% for visual PET analysis.
Conclusions:
- Brain [¹⁸F]-FDG PET/CT reveals a characteristic metabolic signature for AE, aiding in its differentiation from other neurological conditions.
- The study supports [¹⁸F]-FDG PET/CT as a valuable complementary diagnostic biomarker for AE, particularly in younger patient populations.
