First-in-human implantation of a mid-field powered neurostimulator at the sacral nerve: Results from an acute study.

INTRODUCTION: Commercially approved implantable systems for sacral neuromodulation require the implantation of a multipolar lead subcutaneously connected to an implantable pulse generator (IPG). Eliminating the need for an IPG would eliminate the need for tunneling of the lead, reduce procedure time, infection risk, and the need for IPG replacement. The objective was to demonstrate the feasibility of implanting the AHLeveeS System in the S3 Foramen to stimulate the S3 sacral nerve. MATERIALS AND METHODS: A first-in-human, prospective, single center, nonrandomized, acute feasibility clinical investigation at the Maastricht University Medical Center+. Patients with refractory overactive bladder underwent acute implantation of the AHLeveeS neurostimulator before the InterStim procedure. Outcome measurements included motor responses, procedural time and a scoring of the difficulty of the implant and explant procedure. Retrospectively, qualitative responses to the stimulation protocol were assessed by video motion analyses. Only descriptive statistics were used. RESULTS: During the stimulation a motor response to stimulation was seen in four of the five subjects. In all implantations the AHLeveeS was correctly placed. The median time for complete procedure was 24 minutes. The implant and explant procedures were successfully performed and no device or procedure related adverse events occurred. CONCLUSIONS: The results from this acute first-in-human study demonstrate the feasibility of implantation and acute stimulation of the sacral nerve with this mid-field powered system. Future clinical studies will focus on safety and efficacy of a chronically implanted device.

Modeling dermatome selectivity of single-and multiple-current source spinal cord stimulation systems.

A recently published computational modeling study of spinal cord stimulation (SCS) predicted that a multiple current source (MCS) system could generate a greater number of central points of stimulation in the dorsal column (DC) than a single current source (1 CS) system. However, the clinical relevance of this finding has not been established. The objective of this work was to compare the dermatomal zone selectivity of MCS and 1 CS systems. A finite element method (FEM) model was built with a representation of the spinal cord anatomy and a 2 × 8 paddle electrode array. Using a contact configuration with two aligned tripoles, the FEM model was used to solve for DC field potentials across incremental changes in current between the two cathodes, modeling the MCS and 1 CS systems. The activation regions within the DC were determined by coupling the FEM output to a biophysical nerve fiber model, and coverage was mapped to dermatomal zones. Results showed marginal differences in activated dermatomal zones between 1 CS and MCS systems. This indicates that a MCS system may not provide incremental therapeutic benefit as suggested in prior analysis.

Computational modeling analysis of a spinal cord stimulation paddle lead reveals broad, gapless dermatomal coverage.

Spinal cord stimulation (SCS) is an effective therapy for treating chronic pain. The St. Jude Medical PENTA(TM) paddle lead features a 4 × 5 contact array for achieving broad, selective coverage of dorsal column (DC) fibers. The objective of this work was to evaluate DC activation regions that correspond to dermatomal coverage with use of the PENTA lead in conjunction with a lateral sweep programming algorithm. We used a two-stage computational model, including a finite element method model of field potentials in the spinal cord during stimulation, coupled to a biophysical cable model of mammalian, myelinated nerve fibers to determine fiber activation within the DC. We found that across contact configurations used clinically in the sweep algorithm, the activation region shifted smoothly between left and right DC, and could achieve gapless medio-lateral coverage in dermatomal fiber tract zones. Increasing stimulation amplitude between the DC threshold and discomfort threshold led to a greater area of activation and number of dermatomal zones covered on the left and/or right DC, including L1-2 zones corresponding to dermatomes of the lower back. This work demonstrates that the flexibility in contact selection offered by the PENTA lead may enable patient-specific tailoring of SCS.