A narrative review of serum biomarkers in progressive supranuclear palsy, corticobasal syndrome, and related disorders.

This narrative review evaluates the diagnostic potential of serum biomarkers for progressive supranuclear palsy (PSP), corticobasal syndrome (CBS), and related neurodegenerative diseases. Hyperphosphorylated tau species (p-tau), particularly p-tau217 and p-tau181, show promise in distinguishing PSP and CBS from other neurodegenerative diseases, though not from each other. While serum neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) exhibit limited individual utility, their combination with p-tau species enhances diagnostic accuracy. Other genome-associated, inflammatory, metabolic biomarkers, and neuropeptides yield interesting though inconsistent results. The majority of serum biomarkers yielded non-specific results in differentiating PSP and/or CBS from each other and from other related neurodegenerative diseases. Future large-scale, multi-center studies with autopsy confirmation in early-stage patients are essential for developing reliable biomarker panels. Direct comparative studies of PSP and CBS subtypes are also necessary for accurate phenotypic discrimination.