Excessive Daytime Sleepiness Following Deep Brain Stimulation (DBS) in Parkinson's Disease (PD): A Systematic Review

Introduction: Excessive daytime sleepiness (EDS) is a frequently-reported symptom of PD significantly affecting quality of life (QoL) in both patients and caregivers. While the benefits of DBS for motor symptoms in PD are well-established, its effect on sleep dysfunction, particularly EDS, is less clear.

This systematic review aims to consolidate evidence on the effects of DBS on EDS in PD. By evaluating methodological constraints in existing studies, this analysis aims to inform future research on the pathophysiology of sleep dysfunction to optimize clinical benefit from DBS on sleep related QoL.

Methods: A PRISMA-compliant systematic review across PubMed, Scopus, and Embase was conducted for studies evaluating preoperative and postoperative EDS in PD using at least one standardized measure after DBS surgery.

Results: Of 169 records, 21 articles met inclusion criteria, comprising 526 total patients with a mean disease duration of 12.3 years. Post surgical follow-up intervals ranged from 1 week to 9 years. Only 4 studies investigated correlations between reduced levodopa equivalent dosage (LED) and EDS scores, with 3 finding EDS improvement independent of medication reduction. 11 of the 18 studies evaluating subthalamic nucleus (STN) implantation found an improvement in EDS, while 7 reported no changes. GPi (n=1) found no improvement, while PPN (n=1) and microsubthalamotomy (n=1) found improvement. 19 studies (90.48%) utilized the Epworth Sleep Scale to measure EDS, while 10 (47.62%) used Parkinson’s Sleep Scale, and 2 (9.52%) Pittsburgh Sleep Quality Index.

Conclusion : Our findings suggest that STN DBS may improve EDS after surgery in PD patients independently of post-DBS LED reduction. This suggests that EDS may be related to a pathological feature of PD that is positively affected by neuromodulatory effects of DBS, rather than a function of antiparkinsonian medication. Further investigation is warranted to understand this effect for different anatomical targets, as well as the impact of EDS on caregiver burden.