Corticobasal degeneration: advances in clinicopathology and biomarkers.

PURPOSE OF REVIEW: Corticobasal degeneration (CBD) is a rapidly progressive neurodegenerative tauopathy diagnosed postmortem by pathological examination. The clinical presentation of corticobasal syndrome (CBS) is an apraxic, dystonic, and rigid limb with asymmetrical cortical signs and myoclonus. However, less than half of the patients with CBS receive a CBD diagnosis. As tau-lowering therapies have entered clinical trials, improved antemortem diagnosis of CBD is needed. Here, clinicopathological, neuroimaging, and biofluid data in CBS and/or CBD patients are briefly summarized and some knowledge gaps identified.

RECENT FINDINGS: Developments of MRI-based and nuclear medicine imaging modalities have increased pathophysiological insights of CBS and may improve diagnostic accuracy. In particular, several tau-PET ligands have been evaluated in CBS patients. Cerebrospinal fluid and plasma levels of neurofilament light chain can distinguish CBS from Parkinson's disease but not from other atypical forms of Parkinsonism.

SUMMARY: Structural and functional imaging approaches provide some aid in the diagnosis of CBD but have low-content validity. None of the currently available tau-PET ligands is suitable for detecting straight filament 4repeat tau disease in clinical routine. Biofluid markers reflecting the distinct tau and/or astrocyte disease of CBD are needed. Examining biosamples along with clinical parameters from longitudinally followed patients with autopsy-confirmed CBD diagnosis shall hopefully delineate improved biomarkers.