Is speech function lateralised in the basal ganglia? Evidence from de novo Parkinson’s disease

Background Research on the possible influence of lateralised basal ganglia dysfunction on speech in Parkinson’s disease is scarce. This study aimed to compare speech in de-novo, drug-naive patients with Parkinson’s disease (PD) with asymmetric nigral dopaminergic dysfunction, predominantly in either the right or left hemisphere. Methods Acoustic analyses of reading passages were performed. Asymmetry of nigral dysfunction was defined using dopamine transporter-single-photon emission CT (DAT-SPECT). Results From a total of 135 de novo patients with PD assessed, 47 patients had a lower right and 36 lower left DAT availability in putamen based on DAT-SPECT. Patients with PD with lower left DAT availability had higher dysarthria severity via composite dysarthria index compared with patients with lower right DAT availability (p=0.01). Conclusion Our data support the crucial role of DAT availability in the left putamen in speech. This finding might provide important clues for managing speech following deep brain stimulation.