Clinical Scorecard: Determinants of the Consistency of Intraoperative Assessments in Deep Brain Stimulation for Parkinson's Disease

At a Glance

Key Highlights

• Intraoperative clinical testing aims to identify optimal stimulation sites by assessing motor symptom improvement and side effects.
• Awake DBS procedures may be complicated by intraoperative drowsiness, somnolence, and disorientation occurring in 1–33% of cases, potentially reducing assessment reliability.
• No significant difference in motor symptom improvement was found between awake and asleep DBS procedures in randomized trials and meta-analyses.

Guideline-Based Recommendations

Diagnosis

• Diagnosis of Parkinson's disease and eligibility for DBS should be confirmed by a multidisciplinary team including neurologists, neurosurgeons, and psychiatrists.
• Exclude patients with severe brain atrophy, psychiatric disorders, or other serious conditions prior to surgery.

Management

• Perform bilateral STN-targeted DBS with intraoperative microelectrode recording and clinical testing in awake patients.
• Use MRI-based anatomical targeting for surgical planning, supplemented by CT fusion on the day of surgery.
• Consider L-DOPA withdrawal protocols with substitution by continuous subcutaneous apomorphine prior to surgery to optimize patient condition.
• Employ anesthesiologic protocols minimizing sedation during awake procedures to reduce somnolence and disorientation.

Monitoring & Follow-up

• Intraoperative clinical testing should assess bradykinesia, rigidity, and tremor using standardized UPDRS Part III measures.
• Monitor for side effects including dysarthria, facial or limb contractions, paresthesia, diplopia, ptosis, and eye deviations during stimulation.
• Document improvements in 25% increments compared to baseline at various stimulation amplitudes.

Risks

• Intraoperative somnolence and disorientation may impair the reliability of clinical testing during awake DBS.
• Potential for intracerebral hemorrhage, as evidenced by exclusion of patients with postoperative hemorrhages.
• Side effects from stimulation such as dysarthria and motor contractions necessitate careful threshold testing.

Patient & Prescribing Data

122 Parkinson's disease patients aged 42–75 years undergoing bilateral STN-DBS between 2002 and 2020

Transition from L-DOPA monotherapy withdrawal to apomorphine pump substitution prior to surgery may influence intraoperative patient state; awake-awake-awake anesthesiologic protocol preferred to reduce sedation-related complications.

Clinical Best Practices

• Use MRI acquired 1–2 days prior to surgery under general anesthesia to reduce movement artifacts for optimal surgical planning.
• Apply five parallel microelectrode trajectories per side, omitting those risking critical structures.
• Perform intraoperative clinical testing starting at sensorimotor STN trajectory with incremental stimulation up to 6 mA or until side effects occur.
• Define optimal stimulation site as earliest symptom reduction with high side effect threshold.
• Avoid sedative drugs during awake procedures to minimize intraoperative somnolence and disorientation.

References

• Bejjani et al. MRI-based targeting in DBS
• Randomized trial comparing awake vs asleep DBS procedures
• Meta-analyses on DBS outcomes
• Declaration of Helsinki