Abstracts

Rationale: To study the clinical metabolic characteristics and diagnostic value of 18F-fluoro-2-deoxy-d-glucose positron emission tomography (18F-FDG-PET) in autoimmune encephalitis associated with leucine-rich glioma-inactivated 1 antibody (LGI1 AE). Methods: A total of 34 patients who were diagnosed with LGI1 AE were retrospectively analyzed from October 2014 to June 2018 at the Department of Neurology, in Beijing Tiantan Hospital, the Capital Medical University. The clinical data were collected by searching for electronic medical records. Results: The initial 18F-FDG-PET scan indicated a significant abnormal metabolic pattern in 31 LGI1 AE patients (91%), whereas the MRI abnormal signal has been reported only 20 cases (59%) (P < 0.05). The 18F-FDG-PET metabolic pattern was reversible after treatment, most of the patients showed almost normal uptake of 18F-FDG-PET after discharge. The abnormal metabolic pattern in LGI1-AE subjects presented with hypermetabolism, and the spatial distribution was specially located in basal ganglia (BG) and medial temporal lobe (MTL), BG hypermetabolism was observed in 28 subjects (82%), and 68% patients showed MTL hypermetabolism. A total of 17 patients (50%) presented with faciobrachial dystonic seizures (FBDS) and the remain subjects showed non-FBDS symptom (50% V.S. 50%). BG-only hypermetabolism was detected in 7 subjects in the FBDS subgroup (7/16), but only 1 subject belonged to non-FBDS subgroup (1/15) (44% vs. 7%, P < 0.05). Conclusions: 18F-FDG-PET imaging was more sensitive than MRI in the diagnosis of LGI1 AE. Isolated basal ganglia hypermetabolism was more frequently observed in subjects with FBDS and potentially suggested involvement of basal ganglia. Funding: Project supported by National Key R&D Program of China 2017YFC1307500, Beijing-Tianjin-Hebei Cooperative Basic Research Program H2018206435, Capital Healthy Development Research Funding 2016-1-2011, the National Natural Science Foundation of China (Grant No. 81801280, 81601126).