a 4R tauopathy
Corticobasal degeneration (CBD) is a slowly
progressive neurodegenerative disorder characterized
by an asymmetrical akinetic-rigid syndrome associated
with cognitive (apraxia and aphasia) and extrapyramidal
motor dysfunction (rigidity and dystonia). Moderate dementia
emerges sometimes late in the course of the disease (Rinne
et al., 1994).
shows gliosis, neuronal loss, presence of achromatic
ballooned neurons, neuritic changes and neurofibrillary
tangles (Paulus et al., 1990 ; Ksiezak-Reding et al.,
1994; Feany et al., 1994; Buée-Scherrer et al.,
1996b) and astrocytic plaques.
There is an overlap between progressive
supranuclear palsy (PSP) and CBD (Feany et al., 1996),
and it would be most helpful to distinguish these two
pathologies on a neuropathological or immunochemical
By comparison, CBD is less prevalent, and
usually dysplays a more severe cortical atrophy with
fronto-parietal predominance partly sparing the central
pathology is complex, in that it combines conspicuous
chromatolytic neurons in large numbers without argentophilic
inclusions. Cortico glio-fibrillar plaques have also
been described, as well as aberrant neurites in the white
matter. The degenerative pathology of the basal ganglia
and rhombencephalon is not as sharply targeted on specific
nuclei as in PSP, and also involves a striking number
of chromatolytic neurons. Astrocytic laques are large
with a hollow center, while those from PSP are stained
with anti-tau in their center, (tuffed plaques).
At the biochemical level,
the profile of neurofibrillary tangles is similar to
PSP, as well as the Tau electrophoretic profile (Ksiezak-Reding
et al., 1994 ; Feany et al., 1995a ; Buée-Scherrer
et al., 1996b).
Tau lesions in PSP and CBD are exclusively
composed of tau isoforms with exon 10 (Sergeant
et al, 1999). This is a 4R tauopathy.
The upper tau doublet, so characteristic,
is found in subcortical and cortical areas at the last
stage of the disease, when dementia is observed.
At the biochemical level, we were not able to distinguish
between PSP and CBD: are they at th opposite ends of the