Comparative Analysis of Impulse Control Symptoms Among Individuals Receiving GPi-DBS or STN-DBS for Parkinson's Disease.

OBJECTIVE

Impulse control disorders (ICDs) are a complication of Parkinson's disease (PD) treatment, but whether deep brain stimulation (DBS) affects ICDs remains unknown. Studies have focused on de novo ICDs among individuals receiving subthalamic nucleus DBS (STN-DBS), but the effects of DBS of the globus pallidus pars internus (GPi-DBS) are less understood. Rates and severities of ICDs among individuals receiving GPi-DBS or STN-DBS were compared.

METHODS

Twenty-seven individuals with PD receiving bilateral DBS (17 STN, 10 GPi-DBS) were prospectively enrolled. Before surgery, participants had a neurological and neuropsychological evaluation. At 12-18 months post-DBS, the participants completed an abbreviated battery and an ICD rating scale. Volume of tissue activated (VTA), the intersection of each participant's stimulation volume with atlas-defined subregions of the DBS target, was explored in a sample subset.

RESULTS

GPi-DBS participants had significantly higher post-DBS ICD severity scores compared with STN-DBS participants (p=0.040, Cohen's d=0.73), despite lower presurgical scores. A significant interaction between DBS target and time point (p=0.015, ηp²=0.26) indicated increased ICD symptoms in the GPi group postsurgery. Post-DBS, 80% and 35% of the GPi-DBS and STN-DBS participants met ICD criteria, respectively. Differences in ICDs persisted in analyses controlled for levodopa-equivalent daily dose. ICD improvements post-DBS were linked to greater VTA overlap in STN limbic regions, with no significant VTA associations with GPi-DBS.

CONCLUSIONS

GPi-DBS may increase the risk for de novo ICDs. This observation should be interpreted with caution because of the small sample size and low statistical significance. Additional research may clarify the relationships between DBS targets and ICD outcomes.