The current diagnostic criteria for progressive supranuclear palsy (PSP) were established by the MDS-PSP Study Group and published in 2017, replacing the earlier NINDS-SPSP criteria from 1996. These updated MDS-PSP criteria represent a significant advancement in the clinical recognition of PSP and its phenotypic variants.1

The MDS-PSP criteria define four core functional domains: ocular motor dysfunction, postural instability, akinesia, and cognitive dysfunction. Within each domain, features are graded by diagnostic certainty into three levels of clinical predominance — probable PSP, possible PSP, and suggestive of PSP. The hallmark feature remains vertical supranuclear gaze palsy, particularly of downward gaze, which is considered the most specific clinical marker. However, the updated criteria recognize that this feature may not be present early in the disease course.12

A key contribution of the 2017 criteria is the formal recognition of clinical subtypes, including PSP–Richardson syndrome (PSP-RS), PSP with predominant parkinsonism (PSP-P), PSP with progressive gait freezing (PSP-PGF), PSP with predominant corticobasal syndrome (PSP-CBS), and PSP with predominant speech/language disorder (PSP-SL), among others. Each subtype has distinct diagnostic requirements based on the combination and severity of features across the four domains.1

The criteria also incorporate mandatory exclusion criteria, including the absence of features suggestive of alternative diagnoses such as corticobasal degeneration, multiple system atrophy, or dementia with Lewy bodies. Supportive features include poor response to levodopa, early dysphagia or dysarthria, and specific neuroimaging findings such as midbrain atrophy on MRI.23

The MDS-PSP Rating Scale (PSP-RS) is the recommended instrument for quantifying disease severity across six domains: daily activities, behavior, bulbar function, ocular motor function, limb motor function, and gait/midline. This validated scale is widely used in clinical trials and observational studies to track disease progression.24