It has been suggested that SCS attenuates mechanical hypersensitivity after nerve injury in both an intensity-dependent and frequency-related fashion. In recent studies, investigators have begun to determine how paresthesia-free HF-SCS affects neuropathic pain-related behavior in animal models, and to explore the underlying mechanisms. Notably, clinical success of HF10-SCS was not dependent on eliciting paresthesia that overlapped a patient’s painful areas, which is fundamental to the clinical efficacy of traditional SCS.ĬOMPARISON OF MECHANISMS FOR PAIN INHIBITION BY PARESTHESIA-FREE HF-SCS AND TRADITIONAL SCS Compared to traditional SCS, HF10-SCS had superior long-term efficacy for the treatment of back and leg pain in two randomized and controlled clinical trials. Initial findings of this new paradigm in several clinical trials have been promising, showing that HF10-SCS is highly effective and can provide pain relief after long-term use. The most common frequency used for paresthesia-free ultra HF-SCS is 10 kHz and will be referred to as HF10-SCS. Several years ago, a new SCS paradigm was developed for pain treatment in which high frequency SCS (HF-SCS) was applied at low amplitudes so that the stimulation became sub-threshold for sensory activation and paresthesia-free. Although traditional SCS is still a dominant neurostimulation therapy, with an estimated 50,000 implantations performed annually in the US to treat conditions such as low back pain and peripheral neuropathic pain, there is an increasing need for new stimulation paradigms that improve short- and long-term clinical effectiveness of SCS and expand its common indications. Despite technological improvements, it has been suggested, “no substantial improvement in results has occurred for more than 30 years…”.
However, conventional SCS has several limitations, such as limited clinical indications, suboptimal or inadequate pain inhibition (e.g., non-responders), and progressive reduction of treatment effects over time. This paresthesia-based SCS has proven to be an effective treatment modality for 40–50% of patients with refractory pain conditions, including complex regional pain syndrome and failed back surgery syndrome (FBSS). Inspired by the seminal gate-control theory of pain proposed by Melzack and Wall, the conventional paradigm of SCS utilizes tonic 40–60 Hz stimulation that activates dorsal columns to elicit paresthesia over a patient’s painful region. Physicians in the United States have been using spinal cord stimulation (SCS) to treat chronic pain conditions since it was first developed nearly half a century ago.