Early impairment of narrative discourse complexity in Parkinson's disease without mild cognitive impairment

Patients with Parkinson's disease (PD) and mild cognitive impairment (MCI) have an increased risk of dementia. Identifying cognitive changes that could be present from the early stages of the disease, or which increase the risk of PD-MCI or dementia development is a highly relevant challenge. To date, investigations focusing on narrative discourse in PD-MCI are extremely scarce. The objective of this research was to investigate narrative discourse with the Cookie Theft (CT) picture in patients with PD, with and without MCI, in addition to other classical measures of language production. Moreover, the authors explore which components of language production are associated with the progression of neurological impairment and the diagnosis of MCI.

This observational study included 27 patients, classified as PD with and without MCI, and 24 controls who were evaluated with a set of linguistic instruments, including the CT picture, verbal fluency test (phonemic and semantic) and naming task.

Both PD groups showed a greater number of simple clauses and lower scores in multiclausal utterances and in the complexity index, suggesting decreased discourse complexity. PD-MCI performed poorly in naming and semantic fluency compared to controls. CT picture performance was independent of neurological impairment (Hoehn and Yahr Stage) and global cognition (Montreal Cognitive Assessment Test), in contrast to naming and verbal fluency.

Impairment in narrative discourse in PD can be present regardless of cognitive status and degree of neurological impairment, in contrast to other language production difficulties, which are associated with MCI diagnosis and disease progression.