FDG PET-CT scans are invaluable in the early diagnosis of autoimmune encephalitis when autoantibody assays are inconclusive. Coexisting neoplasms can be detected and response to treatment can be evaluated. Thus FDG PET-CT scans are biomarkers of the disease.

The clinical features, hospital course and outcome were severe in those whose diagnosis was delayed due to lack of FDG PET-CT scans. 53.33% recovered, 40% had sequel and 6.67% died in the PET-CT group while 13.33% recovered, 73.33% had sequel and 13.33% died in the no PET-CT group [p value < 0.001]. FDG PET-CT scans were abnormal in 3.33% in the first, 20% in the second, 33.33% in the third week, 26.67% in the first month and 16.67% after one month of illness. Sequelae like personality and behavior disorders, impaired memory, cognitive decline, refractory epilepsy, focal motor seizures and impaired quality of life were common in the non FDG-PET-CT scan group [p value <0.001].