Imaging Biomarkers in Autoimmune Encephalitis

 

Limbic Encephalitis (LE) is an autoimmune disease defined by subacute short-term memory loss, psychiatric abnormalities and often involves temporal lobe epilepsy. A variety of autoantibodies has been identified and associated with different subtypes of LE. We hypothesize that LE patients show stage-specific, side-specific and sero-specific structural and functional imaging correlates.

Our aim is to use a variety of multimodal imaging techniques, volumetric and surface-based analyses as well as network model approaches to identify those correlates and and utilize them in predictive analyses applying state-of-the-art machine learning approaches. Our hope is not only to differentially describe different entities covered by the umbrella term “limbic encephalitis”, but also contribute to a deeper understanding of the underlying pathologies.

Structural network topology in limbic encephalitis is associated with amygdala enlargement, memory performance and serostatus. Bauer et al. (2020). Epilepsia. [in press] doi: 10.1111/epi.16691.

Fixel-based analysis links white matter characteristics, serostatus and clinical features in limbic encephalitis. Bauer*,  Ernst* et al. (2020). Neuroimage Clin. 27:e102289. doi: 10.1016/j.nicl.2020.102289.

Volumetry of mesiotemporal structures reflects serostatus in patients with limbic encephalitis. Ernst et al. (2016). AJNR 40:2081-89. doi: 10.3174/ajnr.A6289.

Tracts with reduced fiber cross-section in voltage-gated potassium channel (VGKC) autoantibody associated LE (left and middle) and reduced fiber density and cross-section in glutamic acid decarboxylase (GAD) autoantibody associated LE revealed by fixel-based analysis

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Volumetry of hippocampal subfields in early and late stage in patients with VGKC-associated LE shows and stage- and serotype-specific patterns.

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Morphometric analysis of the hippocampus in Temporal Lobe Epilepsy

Temporal lobe epilepsy (TLE) makes up the largest proportion of epilepsy in adults. The hippocampal sclerosis (HS) is the most common etiology, making up two-thirds of all patients, while up to a third of patients with TLE remains without structural abnormalities in conventional neuroradiological MR diagnostics. Neurosurgical resection of the affected hippocampus plays a major role in the treatment of patients with temporal lobe epilepsy, as up to a third of TLE patients suffer from a drug-resistant form. The International League Against Epilepsy (ILAE) developed a semiquantitative assessment for the histological classification of HS, which shows different prognoses for postoperative seizure control and memory  performance in different subtypes. The classification would be of great use for a preoperative therapy decision. We aim to use the differential geometric analysis method subfieldDNA, a tool that allows a structural analysis of mesiotemporal structures, to firstly attempt a preoperative in-vivo classification of the various HS subtypes according to the ILAE and secondly to increase the diagnostic quality of a presurgical radiological investigation and thus reduce the group of TLE patients without MRI abnormalities (MR-negative TLE patients).