Objective: To report the outcome of a DBS paradigm aimed at reducing axial symptoms after prolonged STN DBS.

Background: High frequency stimulation (HFS) is more effective for appendicular than axial symptoms. Low frequency stimulation (LFS) may reduce gait, balance, and speech impairment, but often results in worsening of appendicular symptoms. The interleaving function allows delivery of two programs on each lead. We used this to create a paradigm (interleave-interlink, IL-IL) with a combination of low and high frequencies.

Method: IL-IL consists of two overlapping LFS programs on each lead, with the overlapping area focused around the optimal electrode contact. This area receives HFS providing appendicular symptom control, whereas the non-overlapping areas receives LFS to reduce gait, balance, and speech impairment. A randomized, double-blind, cross-over trial comparing optimized conventional-HFS and IL-IL was completed. Each arm was 2 weeks long in duration. The primary outcome measure was the CGI-S-patient. Secondary outcome measures included CGI-S-clinician, MDS-UPDRS-I-IV, PDQ-39, FOG-Q, stand-walk-sit-test (SWS), and patient preferred setting.

Results: Twenty-five patients (mean 5.57 ± 3.1 years since DBS) were recruited, 20 completed, and 5 dropped out. Fourteen patients preferred IL-IL and 6 conventional-HFS. Carry-over was not detected between sequences so data from each period was combined and the paired t-test was used to compare each setting. The CGI-S patient for gait (p=0.01) and appendicular symptoms (p=0.001), CGI-S clinician for gait (p=0.01) and speech (p=0.02), MDS-UPDRS-III (p=0.002), MDS-UPDRS-IV (p=0.003), PDQ-39 (p=0.002), FOG-Q (0.004), and SWS (p=0.01) were better in the IL-IL group compared to conventional HFS. There was no difference between groups in the CGI-S patient for speech (p=0.24), CGI-S clinician for appendicular symptoms (p=0.18), MDS-UPDRS-I (p=0.26) and the MDS-UPDRS-II (p=0.09). Results are detailed in [table1].

Conclusion: This is the first study demonstrating the effect of combining low and high frequency stimulation on axial symptoms. Patients on the IL-IL paradigm demonstrated an improvement in gait, balance, speech, and quality of life. IL-IL did not provide inferior appendicular symptom control. The IL-IL paradigm may be useful in patients with continued axial symptom impairment that cannot otherwise be controlled with conventional programming techniques.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/dual-frequency-deep-brain-stimulation-paradigm-for-axial-symptoms-in-parkinsons-disease/