Conversion to Hybrid Deep Brain Stimulation System to Enable Multi‐Contact Fractionation Can be Therapeutic

For more than 25 years since its inception, a single-source programmable implantable pulse generator (IPG) was the mainstay technology of modern deep brain stimulation (DBS) systems used for medication-refractory movement disorders. However, multiple independent current control (MICC) was a recent innovation in IPG design, which was approved by the United States Food and Drug Administration. MICC attempts to control current fluctuations and enhance precision delivery by using an independent current source directed to each contact on the electrode lead. Current-control should also allow for the delivered therapy to remain more stable, at least in relation to fluctuations in impedance. Stimulation-induced side effects are commonly reported and these may be related to inherent DBS device limitations. This often leads to the dilemma of administering suboptimal stimulation parameters to avoid side effects. Hence, we postulated that converting a precursor, optimized system with an MICC-ready DBS IPG would be feasible and yield additional therapeutic benefits. This retrospective chart review consisted of 50 adult Parkinson’s disease and essential tremor patients, from which three additional study subsamples were statistically analyzed. All patients presented with single-source, voltage-controlled Medtronic IPG devices and subsequently underwent single conversion to a hybrid DBS system with a Boston Scientific MICC-enabled IPG. Differences in side-effect thresholds (SETs) were retrospectively assessed using Wilcoxon signedrank tests and Shapiro–Wilk tests were used to test normality assumptions. Statistical significance was determined using an alpha of 0.05 (two-tailed). All conversions were successfully undertaken with no surgical complications (eg, infections, reoperations, hardware malfunctions) or complications related to reprogramming. Moreover, there was no adverse effect (eg, unexpected pain, cosmetic deformity, infection, hematoma, wound erosion) in any patient following conversion. Among the Study Subsample patients, there was a statistically significant median difference in SETs at the first postoperative clinic visit compared to before conversion (median 11 days after conversion; left electrode: median 4.0 mA vs. 3.7 mA, P = 0.017; right electrode: 4.2 mA vs. 3.7 mA, P = 0.030; Fig. 1). Nearly 91% of patients received fractionation at the first postoperative visit. Approximately 68% of patients improved in at least one symptom or adverse event at the first postoperative visit. The accompanying supplemental information provides additional details regarding the study methodology, results, and limitations. Among the limitations of our study are the retrospective design and lack of objective movement disorder scales (eg, Unified Parkinson’s Disease Rating Scale), which may have introduced bias. Additionally, the possible restrictions to magnetic resonance imaging of hybrid DBS systems, a possible increase in study-wide error rate, use of a convenience sample at one clinical site, and the unintentional lack of Black/African American patients in our study may have further biased our findings. Our study preliminarily demonstrated that conversion from a single-source system to a hybrid DBS system using an MICCenabled IPG is safe and feasible. The most common reason for conversion was battery depletion. Some patients desired a rechargeable DBS system, which was achievable with the MICC-enabled device. Improvements in SETs evidenced in our