We report the case of a 28-year-old woman presenting behavior disorders of subacute onset. She was referred in our institution for a suspicion of limbic encephalitis. F-FDG PET/CT did not show any mesiotemporal abnormality but depicted a decreased uptake of bilateral parietal and occipital lobes. This atypical pattern was compatible with an anti-N-methyl-D-aspartate receptor encephalitis that was later confirmed.