Cognitive, Motor and Oculomotor Contributions to the Trail Making Test in Progressive Supranuclear Palsy

BACKGROUND: Progressive supranuclear palsy (PSP) is a neurodegenerative disorder characterized by motor, oculomotor and cognitive impairments. Yet disentangling cognitive deficits from motor and oculomotor dysfunction remains a diagnostic and methodological challenge. OBJECTIVES: This study aims to evaluate how cognitive, motor, and oculomotor impairments contribute to performance in the Trail Making Test (TMT) in PSP patients. METHODS: Eighty-one patients with PSP-Richardson's syndrome underwent the Toronto Cognitive Assessment, the Movement Disorder Society Unified Parkinson's Disease Rating Scale-part III and the PSP rating scale. Structural equation modeling was used to examine associations between TMT performance, cognitive function, and motor/oculomotor measures derived from these assessments. RESULTS: TMT performance was mainly driven by cognitive factors, particularly executive function, with no significant influence from motor or oculomotor deficits. CONCLUSIONS: These findings suggest that the TMT is a valuable tool for assessing cognitive impairment in PSP, reflecting fronto-striatal (associative loop) dysfunction rather than motor or oculomotor impairments.