Corticobasal degeneration and its relationship to progressive supranuclear palsy and frontotemporal dementia

In 1967, J. J. Rebeiz, E. H. Kolodny, and E. P. Richardson described three patients with a progressive asymmetrical akinetic-rigid syndrome and apraxia and labeled these cases corticodentatonigral degeneration with neuronal achromasia. They recognized the resemblance of the pathology to Pick’s disease, particularly the neuronal achromasia, also called Pick cells. Although there were few additional reports for the next 20 years, interest in this disorder has increased significantly since the early 1990s, when it was renamed corticobasal degeneration (CBD). The core clinical features that have been considered characteristic of the disorder include progressive asymmetrical rigidity and apraxia, with other findings suggesting additional cortical (eg, alien limb phenomena, cortical sensory loss, myoclonus) and basal ganglionic (eg, bradykinesia, dystonia, tremor) dysfunction. Recently the relationships of CBD to progressive supranuclear palsy (PSP) and frontotemporal dementia (FTD) have been recognized, which include clinical, pathological, biochemical, and genetic features. The terminology relating to CBD is confusing not only because several terms have been applied to the disorder, such as corticonigral degeneration, corticobasal ganglionic degeneration, as well as CBD, but also because the constellation of clinical features may be seen with pathology other than CBD. Others have suggested syndromic terms such as corticobasal syndrome, corticobasal degeneration syndrome, and progressive asymmetrical rigidity and apraxia syndrome. There are reasonable arguments for and against each of the syndromic terms, and although consensus on the terminology has not been established, some now use the term corticobasal syndrome. In this review, we use the term corticobasal syndrome (CBS) to characterize the constellation of clinical features initially considered the defining characteristics of corticobasal degeneration and reserve use of the term corticobasal degeneration (CBD) for the histopathological disorder.