Progressive Dopamine Transporter Binding Loss in Autopsy-Confirmed Corticobasal Degeneration

Abstract

Corticobasal degeneration (CBD) is characterized by neuronal and glial deposition of 4-repeat tau in the frontal and parietal cerebral cortex, white matter and striatum. There is neuronal loss in affected cortical regions and in the substantia nigra (SN). Recent single photon emission tomography (SPECT) studies have reported normal striatal dopamine transporter (DAT) binding in individual patients with CBD. To study the pattern and course of DAT binding loss in CBD. We retrospectively analyzed DAT SPECT studies in two patients presenting with a corticobasal syndrome in whom a diagnosis of CBD was later confirmed pathologically. Baseline scans at 1.5 years after symptom onset revealed only mild abnormalities (reduced uptake in one putamen). Follow up scans at 4.5 years (Case 1) and 5 years (Case 2) after symptom onset showed a marked decline of striatal DAT binding. In both cases, there was a 37% binding reduction from the age-expected striatal binding value. Asymmetry of striatal DAT binding had increased from mild in the first SPECT studies to moderate at the time of their final imaging. CBD patients can have delayed neuronal loss in the SN. Follow up DAT imaging may be of value in patients with possible CBD and a normal baseline scan.