Exploring risk factors for stuttering development in Parkinson disease after deep brain stimulation

Background Stuttering is a speech disorder with disruption of verbal fluency, occasionally present in Parkinson's disease (PD). PD co-incident stuttering may either worsen or improve after Deep Brain Stimulation (DBS). Methods Sixteen out of 453 PD patients (3.5%) exhibited stuttering after DBS (PD-S) and were compared with a group of patients without stuttering (PD-NS) using non-parametric statistics. Results After DBS, stuttering worsened in 3 out of 4 patients with co-incidental stuttering. Most PD-S underwent subthalamic (STN) DBS, but 4 were implanted in the globus pallidus (GPi). Nine out of 16 PD-S (56.3%) reported a positive familial history for stuttering compared to none of the PD-NS. PD-S were mainly male (81.3%) with slight worse motor features compared to PD-NS. Conclusion Herein, we describe a group of PD patients developing stuttering after DBS and report the presence of a positive familial history for stuttering as the most relevant risk factor, suggesting a possible underlying genetic cause. The fact that stuttering occurred after either STN or GPi DBS is an argument against the impact of medication reduction on stuttering.