Corticobasal Syndrome / Degeneration (CBS/CBD)

Clinical Overview

Corticobasal syndrome (CBS) is a clinical syndrome, which belongs to the group of atypical parkinsonian syndromes. CBS is characterised by progressive asymmetric akinetic-rigid parkinsonism, ideomotor apraxia, i.e., the inability to perform skilled gestures upon command, often combined with dystonia, myoclonus, cortical sensory loss, and alien limb phenomenon, where patients have the impression that their limb does not belong to them and is controlled by an external force. There are numerous causes of CBS. The most common cause is corticobasal degeneration (CBD), a 4-repeat (4R) tauopathy. The differential diagnosis includes progressive supranuclear palsy (PSP), Alzheimer's disease and frontotemporal lobar degeneration (FTD) with TDP-43 inclusions, which may clinically also present as CBS. Most CBS cases occur sporadically, but familial CBS has been observed. In the latter, progranulin gene (GRN) mutations are the most common cause of familial CBS. Globally, progranulin mutations are exceedingly rare. Treatment for CBS remains symptomatic with a growing number of clinical trials focusing on this condition.