MAPT and corticobasal degeneration disorder: Astrocytes in TBI cases were moderately immunoreactive for RD4 (4R tau) in two of the three cases (Cases 12 and 13), while 3R tau was absent from astrocytes in all three TBI cases, like what has been observed in ARTAG, progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) control cases [4].