Corticobasal degeneration with neither argyrophilic inclusions nor tau abnormalities: A new subgroup?

In corticobasal degeneration (CBD), cerebral cortical neuronal loss with achromasia and degeneration of the subcortical nuclei, particularly the substantia nigra, are common. Recent studies have suggested that the occurrence of argyrophilic nigral inclusions, resembling the neurofibrillary tangles found in progressive supranuclear palsy, and widespread tau abnormalities may be features of CBD. We studied brain tissues from two patients in whom CBD was suspected clinically. From the distribution of their cortical and subcortical lesions, the patients were diagnosed as having CBD. However, Gallyas/tau-positive neuronal and glial structures were not found, which suggests there may be a subgroup of CBD with neither argyrophilic inclusions nor tau abnormalities.