Determinants of Consistency in Intraoperative Assessments for DBS in Parkinson's Disease

Overview

This retrospective study analyzed 122 Parkinson's disease patients undergoing bilateral STN-DBS to identify factors influencing intraoperative somnolence and disorientation during awake procedures. Findings highlight the impact of anesthesiologic protocols, medication management, and imaging timing on the reliability of intraoperative clinical testing.

Background

Deep brain stimulation (DBS) for Parkinson's disease (PD) traditionally involves awake surgery with intraoperative clinical testing to optimize electrode placement by assessing motor symptom improvement and side effects. However, the necessity of awake procedures has been questioned due to comparable motor outcomes with asleep DBS and challenges such as intraoperative drowsiness and disorientation, which can affect test reliability. This study aims to clarify factors influencing these intraoperative cognitive states to improve awake DBS procedures.

Data Highlights

A total of 122 PD patients (age 42-75, mean 61.8 years) underwent bilateral STN-DBS between 2002 and 2020. Patients were categorized by PD subtype: 57 equivalent type, 48 hypokinetic-rigid, and 17 tremor-dominant. Medication protocols changed over time: from 2002-2008, all PD meds were withdrawn preoperatively; from 2008-2020, L-DOPA was replaced by continuous subcutaneous apomorphine until 1 hour before surgery. MRI timing also varied, with initial patients scanned on surgery day and later patients scanned 1-2 days prior. Anesthetic protocols evolved from asleep-awake-asleep-awake with sedation to awake-awake-awake without sedatives. Intraoperative clinical testing assessed motor improvements and side effects at multiple stimulation intensities and trajectories.

Key Findings

• Intraoperative somnolence and disorientation occurred in 1–33% of awake DBS procedures, potentially reducing test reliability.
• Transition from sedated asleep-awake-asleep-awake protocols to awake-awake-awake protocols without sedatives improved patient alertness during testing.
• Preoperative medication management shifted from complete withdrawal to apomorphine substitution, potentially influencing intraoperative cognitive state.
• Timing of preoperative MRI (day of surgery vs. 1-2 days prior) was standardized to reduce movement artifacts and optimize surgical planning.
• Intraoperative clinical testing utilized multiple microelectrode trajectories and stimulation intensities to identify optimal stimulation sites balancing symptom improvement and side effect thresholds.

Clinical Implications

Optimizing anesthetic management by minimizing sedative use and carefully managing preoperative PD medications can reduce intraoperative somnolence and disorientation, enhancing the reliability of awake clinical testing during DBS. Standardizing imaging protocols and surgical planning further supports accurate electrode placement. These measures may improve clinical outcomes by ensuring precise identification of optimal stimulation sites.

Conclusion

This study identifies key factors influencing intraoperative patient alertness during awake DBS for PD, emphasizing the importance of anesthetic protocols and medication management. Addressing these determinants can enhance the consistency and usefulness of intraoperative clinical assessments.

References

1. Bejjani et al. -- MRI-based Target Planning in DBS
2. Randomized Clinical Trial -- Awake vs Asleep DBS Outcomes
3. Meta-analyses -- Motor Symptom Improvement in DBS
4. Anesthesiologic Approaches in Awake DBS Procedures