Cognitive change after subthalamic deep brain stimulation for Parkinsons disease: a systematic meta-regressive analysis

Parkinson's disease is a progressive neurodegenerative disorder characterised by motor dysfunction and cognitive disruption among other non-motor symptoms. No cure for Parkinson's disease exists. Deep Brain Stimulation of the Subthalamic Nucleus (DBS STN) has been utilised for control of motor symptoms. However, cognitive deficits are commonly reported after implantation, and few exhaustive analyses exist to quantify and explain them. Our systematic review, meta-analyses, and meta-regressions examine within-subjects change across thirteen cognitive domains, from 70 studies and 3000 participants at baseline measurements. Improvement was not observed in any domain, but substantial decline at 12 months was observed for phonemic and categorical fluency, which appeared to stabilise 24 to 36 months. Meta-regression suggests that few study characteristics are predictive of longitudinal outcomes, and we propose that further research into specific surgical or placement effects is necessary to mitigate short-term cognitive change after DBS STN in Parkinson's disease.