[Neuroimaging in corticobasal syndrome].

Recently, several attempts have been made to characterize the clinical symptoms and brain atrophy patterns in pathology-proven corticobasal degeneration (CBD) and corticobasal syndrome (CBS) with known histopathology. CBS is a term which was proposed to characterize the constellation of clinical features initially considered the defining characteristics of CBD. Voxel-based morphometry (VBM) analyses of MRI revealed that frontal lobe involvement is characteristic of CBD. The pathologic substrates for clinical CBS were found to be CBD, Alzheimer's disease (AD), progressive supranuclear palsy (PSP), and frontotemporal lobar degeneration (FTLD) with TAR DNA-binding protein (TDP) inclusions. CBS was associated with perirolandic atrophy, irrespective of underlying pathology. In CBS due to FTLD, atrophy extended into the prefrontal cortex, striatum, and brainstem, whereas in CBS due to AD, atrophy extended into the temporoparietal cortex and precuneus. No functional imaging studies in pathology-proven CBD or CBS with known histopathology have yet been published. PET and SPECT studies have demonstrated decreased glucose metabolism and cerebral blood flow in the fronto-parietal cortex, particularly contralateral to the dominant symptoms in CBS patients. A PET study showed decreased acetylcholinesterase (AChE) activity in the fronto-parietal cortex, as well as a correlation between cortical AChE activity and mini-mental state examination score in CBS patients, suggesting that cholinergic stimulant therapy may be effective for dementia in CBS. Additionally, [18F] 6-fluorodopa PET and dopamine transporter SPECT studies have demonstrated nigrostriatal dopaminergic dysfunction in CBS. Antemortem prediction of CBD will remain challenging until sensitive, specific biomarkers are identified.