Translocator Protein 18 kDa PET Imaging Highlights Asymptomatic Isolated Cerebellar Dysplasia.

Asymptomatic congenital isolated cerebellar malformations diagnosed in adults are very rare.(1) A 62-year-old woman without any cerebellar symptom or sign but with subjective memory complaints and a family history of Alzheimer disease (AD) participated in an AD imaging study. Amyloid and tau PET scans were negative. An incidental cerebellar dysplasia, subtle on MRI, was striking on translocator protein (TSPO) PET (Figure). Dysplastic tissue displaced normal tissue, which allowed for normal function. TSPO is highly expressed by activated microglia and astrocytes. The signal on TSPO PET likely corresponded to the abundant astrocytes present in these malformations, as microglia are not increased.(2)