| Abstract: | A survey of 32 clinically and pathologically evaluated cases of corticobasal degeneration (CBD) revealed three subtypes of cortical lesions. Besides the main subgroup with frontoparietal atrophy, especially with degeneration around the central sulcus, there are at least two subtypes in which the degenerating focus shifts from the central region to the frontal or superior temporal region. Such diversity of degenerating areas of the cerebrum results in the clinical heterogeneity of CBD. In contrast to the diversity of cerebral lesions, affected nuclei in the subcortical regions are rather uniform and their distribution is of diagnostic value. Cytopathologically, CBD is characterized by several types of abnormal cytoskeletal structures in both neurons and glia. They have common epitopes with hyperphosphorylated tau except for ballooned neurons, which are regarded as a pathological hallmark of this disease. Massive Gallyas/tau-positive structures consist of neurofibrillary tangles and pre-tangles in neurons as well as astrocytic plaques, coiled bodies and argyrophilic threads in glia. A part of argyrophilic threads are proved to originate from neuronal element. There is discrepancy between poor formation of solid tangles and massive appearance of Gallyas/tau-positive structures in CBD. The former is detectable by Bodian method whereas the latter is scarcely seen by conventional silver impregnations. This indicates that almost all of Gallyas/tau-positive structures have poor inclination to form solid structures in CBD. Immunohistochemical study with an antibody to the exon 3-derived epitope of tau indicates that the majority of Gallyas/tau-positive structures in CBD originate from glial cells. Differences as well as overlaps between CBD and progressive supranuclear palsy are discussed. |
