[Clinical aspects of corticobasal syndrome].

Corticobasal degeneration (CBD) is a distinct neurodegenerative disorder characterized by widespread neuronal and glial accumulation of abnormal tau protein. The core characteristic clinical features of the disorder include progressive asymmetric akinetic-rigid syndrome with apraxia and features indicative of cortical dysfunction (e.g., cortical sensory loss, alien limb sign, and myoclonus) and basal ganglionic dysfunction (e.g., akinesia and dystonia). Pathological examinations of CBD patients have indicated that several proteinopathies, such as tauopathies, amyloidopathies, TDP-opathies, α-synucleinopathies, and prionopathies, may underlie the same clinical phenotype. Because of this considerable clinicopathologic heterogeneity, experts use the term corticobasal syndrome (CBS) for patients with a clinical diagnosis of CBD, and reserve CBD for those whose conditions have been diagnosed on the basis of neuropathological analyses. In this review, we have focused on the clinical aspects of CBS, including its clinical presentation, diagnostic criteria, and pathological backgrounds that are difficult to predict on the basis of clinical presentation alone. Future studies need to further characterize the natural history of CBS patients by performing serial assessments of clinical, neuropsychological, laboratory, and neuroimaging features, since this information will be necessary for designing future disease-modifying therapies that specifically target dysfunction of the 4-repeat tau protein.