Objective: To assess the role of striatal dopaminergic terminals in early de novo (untreated) Parkinson’s disease (PD) patients with impairment of speech.

Background: Dopamine has modulatory influences on the functional organization of the brain circuits which control normal human speech. Abnormal dopamine release in striatum results in speech difficulties. Nearly 90% of PD patients develop speech difficulties during the course of their disease.

Methods: Data of 412 early de novo PD patients using the Parkinson’s Progression Marker’s Initiative database were analyzed. Speech difficulties were defined as UPRDS Part-II, Item 5 (Speech) ≥ 1. The integrity of dopaminergic terminals was quantified with [123I]FP-CIT SPECT molecular imaging, which is a marker of dopamine transporters (DAT) in vivo.

Results: 42.5% (179/421) PD patients showed speech difficulties. PD patients with speech difficulties had lower [123I]FP-CIT uptake (0.74±0.25 in Putamen and 1.85±0.54 in Caudate) compared to PD patients without speech difficulties (0.89±0.31 in Putamen and 2.1±0.54 in Caudate). Lower [123I]FP-CIT uptakes were correlated with speech difficulties (Putamen r2=0.066; p<0.0001, Caudate r2=0.047; p <0.0001). These correlations were significant even when adjusted for age, gender, UPDRS Part-III scores, H&Y stage and Scopa-Aut.

Conclusions: Early PD patients with speech difficulties had more impaired striatal dopaminergic terminals compared to those with normal speech, and the severity of speech difficulties was associated with severity of striatal dopaminergic terminal loss. Our findings suggest a dopaminergic substrate underlying the development of speech impairment in PD, and speech impairment as a potential marker of disease severity.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-role-of-striatal-dopaminergic-terminals-in-early-de-novo-pd-patients-with-speech-impairment/