We report the case of a 73-year-old woman presenting sudden blindness caused by bilateral simultaneous central retinal artery occlusion revealed by ophthalmoscopy. Temporal artery biopsy confirmed the giant cell arteritis. The patient was treated with a systemic steroid without visual recovery. FDG PET/CT was performed 6 months later in the context of persistent inflammatory syndrome. This case shows the close relationship between functional activity and glucose energy metabolism. We observed both bilateral occipital hypometabolism corresponding to loss of functional activity and bilateral temporal (auditory areas) and orbitofrontal hypermetabolism related to compensatory neuronal plasticity.