The purpose of this study is to assess the changes in axial and non-motor symptoms (NMS) following deep brain stimulation of the subthalamic nucleus (STN-DBS) for patients with Parkinson’s disease (PWPD).

Multiple studies have established that STN-DBS is effective for improving Parkinson’s Disease (PD) motor symptomatology. However, mixed reports in the literature regarding the impact of STN-DBS on axial symptomatology and NMS underline the need to establish a clear consensus concerning the interaction of STN-DBS with NMS for PWPD.

58 consecutive PWPD, enrolled in our inter-university (McGill University and Université de Montréal) functional neurosurgery program,  and underwent our pre and post surgical evaluation protocol, were included in this study. Patients were assessed 1 to 3 months prior to surgery and 7 to 18 months post-surgery in the ON-medication state. Standardized scales measuring axial parameters, NMS, mood  and cognition were administered.

The Mini-Best scale showed a significant deterioration (p=0.035) in the post-DBS analysis. There were no significant changes post-DBS in other axial scales. Subgroup analysis did not demonstrate significant differences between sex, age and disease duration.  

A significant decrease in semantic and phonemic fluency (p<0.05) post-DBS, was observed ; while MoCA scores remained stable. Subgroup analysis demonstrated that the older patients had a greater loss of phonemic fluency post-DBS than the younger patients (p=0.016).

There was no significant improvement in QoL (p=0.120). Subgroup analysis showed a tendency in younger candidates for a better QoL post-DBS (mean difference=13.39, p=0.055). Other NMS scales and further subgroup analysis failed to show a statistically significant difference post DBS intervention.

This study demonstrated a negative trend of STN-DBS on axial stability and fluency in PWPD. It also exposed a possible fragility of the older candidates to deterioration of phonemic fluency and possibly QoL post-DBS. These observations should be considered when selecting PWPD for STN-DBS.