[The diagnostic challenge of corticobasal degeneration: distinction between clinical syndrome and pathology]

Corticobasal degeneration (CBD) is a neurodegenerative disease characterised by linear progression, asymmetrical and extrapyramidal symptoms such as rigor and dystonia, as well as by variable cortical symptoms including apraxia, cortical sensory deficits, the alien limb phenomenon and myoclonism of the reflexes. Pathological changes of CBD consist of characteristic taupathology in the gray and white matter. However, there are also patients with neurodegenerative diseases with a different underlying pathology that nevertheless appear clinically as CBD. For that reason, the term corticobasal syndrome (CBS) is commonly used to describe the clinical features, whereas the term CBD is reserved for the pathological entity. Moreover, patients with the typical pathology of CBD can present clinical signs consistent with a clinical diagnosis of Alzheimer's disease (AD) or progressive supranuclear palsy (PSP). We demonstrate this clinico-pathological heterogeneity by presenting two illustrative case reports. The first patient developed the typical clinical symptoms of progressive supranuclear palsy, while exhibiting pathologically CBD. The second patient showed clinical signs of CBS, although pathologically she was diagnosed with Alzheimer's disease. These exemplary cases underscore the need to distinguish carefully between the clinical syndrome of CBS and the pathologically defined entity of CBD.