Abstracts

Rationale: Current diagnostic criteria for patients with AE is more dependent on antibody detection. Recently, many studies had found that ¹⁸F-FDG-PET might play a critical role in the early diagnosis of AE and in subsequent prognostic assessment. Thus, this study summarizes the latest progress of ¹⁸F-FDG-PET findings in patients with AE, to provide a functional imaging basis for AE diagnosis and prognostic assessment.

Methods: A comprehensive ¹⁸F-FDG-PET analysis of AE was carried out in Beijing Tiantan Hospital, Capital Medical University between July 2015 and May 2021, and some cases and studies were from literature by querying the PubMed databases. Included patients or studies had to satisfy the following criteria: (1) definite AE according to the current recommendations or antibody test (2) and all cases scanned with ¹⁸F-PET/CT/MRI examination and imaging findings.

Results: A total of 158 AE patients were included in this study combined with previous literature reports. There were 48 cases of NMDAR, 65 cases of LGI1, 5 cases of CASPR2, 22 cases of GABAB, 15 cases of GAD65 and 3 cases of AMPAR. (1) For NMDAR antibody encephalitis, the main manifestations of hypermetabolism were basal ganglia (16 cases, 33%), medial temporal lobe (14 cases, 29%), frontal lobe (11 cases, 23%), and cerebellum (7 cases, 15%). The hypometabolic patterns were: occipital lobe (30 cases, 63%), parietal lobe (20 cases, 42%), frontal lobe (12 cases, 25%), temporal lobe (10 cases, 29%), basal ganglia (3 cases, 6%), and thalamus (2 cases, 4%). (2) In patients with LGI1 antibody encephalitis, the hypermetabolic pattern was presented: basal ganglia (50 cases, 77%), medial temporal lobe (40 cases, 62%), frontal lobe (4 cases, 8%), cerebellum (4 cases, 8%). In addition, 17 patients with LGI1 antibody encephalitis exhibited faciobrachial dystonic seizures (FBDS), basal ganglia hypermetabolism was more detected in the FBDS subgroup than those in the non-FBDS subgroup (P < 0.05). (3) For CASPR2 antibody encephalitis, hypermetabolic pattern was observed: basal ganglia (2 cases), thalamus (1 case); Hypometabolic pattern: medial temporal lobe (1 case), occipital lobe (1 case). (4) For GABAB antibody encephalitis, it showed hypermetabolic pattern: medial temporal lobe (18 cases, 82%); Hypometabolic pattern: whole cerebral cortex (4 cases, 18%). (5) For GAD65 antibody encephalitis, it showed hypermetabolic pattern: basal ganglia (5 cases, 33%), medial temporal lobe (4 cases, 27%); Hypometabolic pattern: medial temporal lobe (12 cases, 80%), cerebellum (3 cases, 20%), whole cerebral cortex (2 cases, 13%); (6) For AMPAR antibody encephalitis: hypermetabolic pattern: temporal lobe (1 case), cerebellum (1 case); Hypometabolic pattern: whole cerebral cortex (1 case).