Patients with early-stage Parkinson’s disease and left-sided brain dopamine deficits may show greater speech difficulties, according to a recent study. 

In the study, published in Neurology, Neurosurgery, and Psychiatry, researchers examined lateralized speech function in the basal ganglia among patients with de novo Parkinson’s disease (PD). They sought to better understand whether left-hemisphere dopaminergic dysfunction may be associated with changes in speech function. The study included 135 drug-naive patients with PD and employed dopamine transporter (DAT) single-photon emission computed tomography imaging to assess asymmetry in nigral dopaminergic availability. The researchers divided the patients into groups with either right-side (n = 47) or left-side (n = 36) dopaminergic asymmetry.

The researchers observed that the patients with left-sided DAT asymmetry had significantly higher dysarthria severity compared with those with right-sided asymmetry (P = .01), as measured by a composite dysarthria index (CDI). The CDI incorporated variables such as imprecise consonants, monopitch, and prolonged pauses, with left-dominant patients showing a trend toward increased severity in consonant imprecision (P = .08) and reduced pitch variability (P = .06). Furthermore, the study found a moderate negative correlation between dysarthria severity and left DAT availability (r = –0.22, P = .01), indicating an association between left basal ganglia dopaminergic dysfunction and speech function in PD.

The findings may be relevant for therapeutic considerations, particularly with deep brain stimulation, a common intervention for motor symptoms in PD.

Full disclosures can be found in the published study.