Connected speech in progressive supranuclear palsy: a possible role in differential diagnosis

Background Progressive supranuclear palsy (PSP) is an atypical Parkinsonism characterized by motor and neuropsycological disorders. Language could be impaired in PSP patients, also in Richardson variant (PSP-RS). The analysis of connected speech is used in neurodegenerative disorder to investigate different levels of language organization, including phonetic, phonological, lexico-semantic, morpho-syntactic, and pragmatic processing. Objective In our study, we aimed to investigate the language profile, especially connected speech, in early-stage PSP-RS and Parkinson’s disease (PD) patients without predominant speech or language disorders. Methods Language was assessed using the Screening for Aphasia in NeuroDegeneration (SAND); connected speech analysis was conducted from the picture description subtest. Results We enrolled 48 patients, 22 PD and 26 PSP (18 PSP-RS and 8 non-RS). PSP-RS patients presented an impairment in language domain, particularly regarding connected speech. PSP-RS patients presented worse performances than PD in different scores. The output of PSP-RS patients was characterized by a reduction in number of sentences and subordinates with respect to PD; PSP presented also more repaired sequences and phonological and lexico-semantic errors than PD. Number of sentences and number of subordinates of the picture description task were identified as predictors of PSP diagnosis. Conclusion In summary, the SAND scale is able to identify language impairment in PSP patients. The analysis of connected speech could highlight some important aspects of language impairment in PSP-RS patients, and it could be helpful in the differential diagnosis with PD.