Impact of Confirmed Autoimmune Encephalitis on Brain Glucose Metabolism

Study Overview
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Brief Summary
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Prospective cohort study evaluating FDG PET in 56 patients with confirmed autoimmune encephalitis - based on 2016 Graus criteria, and 2021 paraneoplastic neurological syndromes criteria - at the acute phase, before immunomodulating treatment, or within 10 days of treatment initiation.

Detailed Description
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Autoimmune encephalitis is a diagnostic challenge, and requires early diagnosis for improved neurological outcomes. FDG PET has shown very high sensitivity, suggesting better performances than MRI, but almost exclusively in small sized retrospective studies. Brain FDG PET is therefore not included in current diagnostic criteria, conversely to brain MRI. This study will include 56 patients with confirmed - seropositive or seronegative - autoimmune encephalitis, based on 2016 Graus criteria for autoimmune encephalitis and 2021 criteria for paraneoplastic neurological syndromes. The main objective is to conduct a prospective evaluation of the diagnostic value of FDG PET performed in the acute phase before treatment initiation, or within 10 days of treatment initiation. A follow-up PET performed 3 months after treatment initiation will also be performed and analysed for all patients as part of secondary objective analyses.

Official Title
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Impact of Confirmed Autoimmune Encephalitis on Brain Glucose Metabolism : a Prospective FDG PET Study

Conditions
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Autoimmune Encephalitis

Intervention / Treatment
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* Other: FDG PET


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age ≥ 18 years old Newly diagnosed autoimmune encephalitis based on at least 1 of the 3 following criteria :  Definite limbic autoimmune encephalitis  according to 2016 Graus et al. criteria Possible autoimmune encephalitis  according to 2016 Graus et al. criteria AND typical autoantibody detected in serum or CSF Probable or certain paraneoplastic neurological syndrome  according to Graus et al. 2021 criteria (excluding peripheral neurological syndromes) Less than 6 months since first neurological symptoms imputable to autoimmune encephalitis Affiliated or entitled to a social security system (except AME) Obtaining free, written and informed consent (patient or legal representative or the close relative) Exclusion criteria History of brain tumor, head trauma, infarction or cerebral hematoma likely to result in altered cerebral carbohydrate metabolism on PET Patients who hae been on immunotherapy (corticosteroid bolus, IVIg, plasma exchange, endoxan, rituximab or other immunotherapy) fr more than 10 days Pregnant or breast-feeding woman Ventilated intubated patient Absolute contraindication to MRI (Pacemaker, cochlear implant, etc.) Presence of cognitive disorders incompatible with goog cooperation with the PET scan Algic or agitated patient unable to remain immobile in supine position for 30 minutes Deprived of liberty or under a protective measure (guardianship or curatorship) Patient taking part in other interventional research involving radiopharmaceutical injections

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: FDG PET<br> | Other: FDG PET<br>* Brain FDG PET performed 3 months after treatment initiation<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Main analysis of initial brain FDG PET | Automated region-based and voxel wise quantitative PET analysis, estimation of the proportion of patients with PET anomalies (overall and by region of interest). | PET performed at the acute phase, before immunomodulating treatment (or within 10 days of treatment initiation) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Analysis of follow-up brain FDG PET | Automated region-based and voxel wise quantitative PET analysis comparatively to initial brain PET | PET performed 3 months after treatment initiation, compared to initial brain PET | 
| Secondary analysis of initial brain FDG PET | Subgroup PET analysis according to autoantibody subtype or seronegative status | PET performed at the acute phase, before immunomodulating treatment (or within 10 days of treatment initiation) | 
| Secondary analysis of initial brain FDG PET | Correlation of main analysis results to important clinical variables (clinical symptomatology (typology and duration of symptoms), MRI, cerebrospinal fluid (CSF), electroencephalogram (EEG).) | PET performed at the acute phase, before immunomodulating treatment (or within 10 days of treatment initiation) | 
| Secondary analysis of initial brain FDG PET | PET voxel-wise connectivity analysis | PET performed at the acute phase, before immunomodulating treatment (or within 10 days of treatment initiation) | 
| Secondary analysis of initial and follow-up brain FDG PET | Correlation of PET treatment response to clinical symptom treatment response | PET performed at the acute phase, before immunomodulating treatment (or within 10 days of treatment initiation), and follow-up PET 3 months after treatment initiation | 
| Analysis of initial whole body FDG PET | Evaluation of whole body FDG PET diagnostic performance for identifying neoplasms in paraneoplastic syndromes | PET performed at the acute phase, before immunomodulating treatment (or within 10 days of treatment initiation) | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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LGI1, CASPR2, GAD, Autoimmune Encephalitis, PET, FDG, NMDAr