At the screening visit, each subject and the caregiver will be asked to provide written informed consent or assent. During the screening phase (maximum duration - 28 days) subject medical, neurological and surgical history, clinical assessments and a neuro-psychiatric evaluation will be performed on all eligible subjects. Subjects will be allowed to leave the center after all evaluations have been completed. During this period an MRI of the brain must be performed. During the MNI-558 PET imaging day, all subjects will receive a single IV injection of IMP and scanning will be performed from 0-60 min, 75-135 min, and 150-210 min (p.i). Each subject will be asked to return to the site for a follow-up visit (20 to 28 hours after IMP administration) and a telephone follow-up will occur 7 days thereafter. Safety will be assessed during both follow-up visits.