Clinical Research Directory

Metabolic Imaging for Diagnosis and Prognostication of Autoimmune encephalitiS

Autoimmune encephalitis (AE) is a rare neurological disorder mediated by autoimmune antibody response against neuronal cell surface and intraneuronal proteins associated with specific brain areas, resulting in severe inflammation and damage in the associated brain regions, all most frequently manifesting diverse cognition and memory impairment symptoms at follow-up. However, these symptoms may co-exist or mimic other CNS autoimmune and neurodegenerative disorders. The most common guideline for diagnosing autoimmune encephalitis relies on cerebrospinal fluid (CSF) antibody testing which might take several weeks to obtain, making it not optimal for the early diagnosis of AE. As for magnetic resonance imaging (MRI), which is the most common imaging tool utilized for aiding in the diagnosis of AE, can possess several limitations as some patients, like anti-NMDAr AE patients, can present memory and behavioral deficits even in the presence of normal brain MRI. Positron emission tomography (PET) with 2-deoxy-2-\[fluorine-18\] fluoro-D-glucose (18F-FDG) have been addressed by several studies as an important examination for the early diagnosis of AE . One study demonstrated that the fraction of having an abnormal MRI in AE patients is lower than having an abnormal PET, by which certain PET patterns were associated with autoantibody types of AE. Moreover, one report demonstrated that even with autoantibody negative test and normal brain MRI, FDG-PET examination showed abnormal hypometabolism and hypermetabolism patterns. More specifically, these distinct patterns include medial temporal and striatal hypermetabolism with cortical diffuse hypometabolism. Leiris et al. revealed that the methadology used for the analysis of these PET images is highly variable, especially intensity normalization methods, where most possess some limitations (e.g., proportional scaling) as they can impede the accurate differential diagnosis of autoimmune encephalitis (AE) by potentially indicating false hypermetabolism in otherwise preserved brain regions. Absolute quantification is not possible since the disease presents both diffuse hypometabolism and hypermetabolism on PET images. So, they suggested that it's best to parametrize the brain's activity by dividing it by that of the striatum. Their voxel-based analysis, comparing individuals with AE to both healthy subjects and those with mild cognitive impairment (MCI), demonstrated that a decrease in the cortex/striatal metabolic ratio is a robust biomarker for the early diagnosis of AE.

Characterization of Immune-response in Autoimmune Encephalitis and Paraneoplastic Neurological Syndromes

Autoimmune encephalitis (AE) and paraneoplastic neurological syndromes (PNS) are rare neuroimmune syndromes with a wide range of clinical presentation but without pathognomonic clinical sign facilitating the diagnosis. A lot of differential diagnoses are possible such as neurodegenerative diseases or viral infections. Although rare the diagnosis of AE or PNS is essential because despite severe neurological symptoms, patients can be cured by appropriate immunotherapy. Autoantibodies highly specific of AE and PNS has been described in the serum and cerebrospinal fluid of the patients and can be used as biomarkers of the disease. Their presence can predict an autoimmune origin and in many cases a good prognosis after immunotherapy. However, if some autoantibodies are now well-characterized and industrial kits have been developed to detect them, in numerous cases of highly suspect AE or PNS no specific autoantibodies are identified leading frequently to an inappropriate treatment. Furthermore, as the mechanisms of AE and PNS is still unknown, treatments are not optimal and in some cases inefficient. There is no prognosis biomarker able to predict the patient's sensitivity to immunotherapy and there are only few clues to know how the immune system can provoke the neuropsychiatric symptoms observed in the patients.

New Biomarkers in Auto-immune Encephalitis and Neurological Paraneoplastic Syndromes

Autoimmune encephalitis (AE) and paraneoplastic neurological syndromes (PNS) are rare neuroimmune syndromes with a wide range of clinical presentation but without pathognomonic clinical sign facilitating the diagnosis. A lot of differential diagnoses are possible such as neurodegenerative diseases or viral infections. Although rare the diagnosis of AE or PNS is essential because despite severe neurological symptoms, patients can be cured by appropriate immunotherapy. Autoantibodies highly specific of AE and PNS has been described in the serum and cerebrospinal fluid of the patients and can be used as biomarkers of the disease. Their presence can predict an autoimmune origin and in many cases a good prognosis after immunotherapy. However, if some autoantibodies are now well-characterized and industrial kits have been developed to detect them, in numerous cases of highly suspect AE or PNS no specific autoantibodies are identified leading frequently to an inappropriate treatment. Furthermore, as the mechanisms of AE and PNS is still unknown, treatments are not optimal and in some cases inefficient. There is no prognosis biomarker able to predict the patient's sensitivity to immunotherapy and there are only few clues to know how the immune system can provoke the neuropsychiatric symptoms observed in the patients. The investigators will use this project to better characterize AE and PNS patients to identify new diagnostic and prognostic biomarkers and develop new diagnostic tools.