Exploration of High- and Low-Frequency Options for Subperception Spinal Cord Stimulation Using Neural Dosing Parameter Relationships: The HALO Study.

OBJECTIVES: Subperception spinal cord stimulation (SCS) is described mostly utilizing waveforms that require high energy. However, the necessity of these waveforms for effective subperception has not been established. We aimed to explore whether effective subperception pain relief can be achieved using frequencies below 1 kHz. MATERIALS AND METHODS: Thirty chronic pain patients implanted with SCS were enrolled as part of a multicenter, real-world, consecutive, observational case series. An effective stimulation location was determined using a novel electric field shape designed to preferentially modulate dorsal horn elements. Subsequently, programs at lower frequencies (600, 400, 200, 100, 50, and 10 Hz) were provided with pulse-width and amplitude adjusted to optimize response. RESULTS: All tested frequencies (1 kHz down to 10 Hz) provided effective subperception relief, yielding a mean of 66-72% reduction in back, leg, and overall pain. It was found that to maintain analgesia, as frequency was decreased, the electrical or "neural" dose had to be adjusted according to parameter relationships described herein. With the reduction of frequency, we observed a net reduction of charge-per-second, which enabled energy savings of 74% (200 Hz) and 97% (10 Hz) relative to 1 kHz. Furthermore, pain reduction was sustained out to one year, with 85% of patients reporting a preference for frequencies of 400 Hz or below. CONCLUSIONS: We have derived an electric field configuration and, along with previous learnings in the kHz range, a set of neural dosing parameter relationships (10-10,000 Hz), which enable the expansion of effective subperception SCS to low frequency and achieve major energy savings.