A 32-year-old woman, with spare previous medical history, presented with neurological symptoms of numbness and diplopia. The patient underwent brain MRI, which revealed a lesion of abnormal signal in the midbrain that could be attributed to subacute stroke; however, consecutive MRIs revealed multiple lesions of abnormal signal pointing to demyelinating disease. During symptoms investigation and MRI findings assessment, the patient underwent a FLT PET/CT examination, which revealed lesions of increased FLT uptake, probably indicating active disease and blood-brain barrier disruption.