Sub-Sensory Intraspinal Neurostimulation Therapy

Chronic pain remains a serious public health problem, resulting in approximately 100 million
chronic pain patients in the U.S. alone [1]. While numerous treatments exist, none
completely addresses this issue. In particular, spinal cord stimulation (SCS) has become an
established technique for treating patients with chronic neuropathic pain [2]. The
conventional paradigm for SCS treatment is to attempt to mask the pain by substituting the
pain sensation with paresthesias [3]; however, newer studies have shown that it is possible
to gain excellent pain relief without concomitant paresthesias ("sub-threshold stimulation")
using different stimulation parameters [4] [5]. Because these paresthesia-free programming
paradigms are still new, the best to place the stimulation and the best programming
parameters to use is still unclear, making it difficult to place the leads during surgical
implantation and to program the patient afterwards. Additionally, sub-threshold stimulation
does not provide immediate pain relief, but may take several hours or even days to feel
relief, making a simple programming session of a few hours insufficient to determine the
optimal stimulation placement. While these differences from conventional SCS make
programming more difficult initially, studying this new stimulation paradigm, especially
differences in optimal stimulation location and the time course of pain relief, may also
provide insight into the mechanism of action of sub-threshold stimulation. This protocol
aims to study the optimal stimulation parameters and locations with SCS using sub-threshold
stimulation.

Inclusion Criteria:

- Primary pain complaint of persistent or recurrent low back and/or leg pain, with or
without leg pain, for at least 180 days prior to Baseline.

- Received a Boston Scientific SCS System with active contacts located between superior
endplate of T7 and the inferior endplate of T10 with a minimum of three active
contacts within this anatomical area.

- No back surgery within 180 days prior to Baseline.

- Has had stimulator "on" (activated or operational) for at least 36 hours prior to
Baseline evaluation.

- Average low back and/or leg pain intensity, during the position/activity which
routinely causes worst pain, of 5 or greater on a 0-10 numerical rating scale without
neurostimulation.

- If taking prescription opioids for primary chronic pain complaint (low back and/or
leg pain), must have been on a stable prescription (same drug(s) and dose(s)) for 30
days prior to Baseline

- Consumed an average total daily morphine equivalent of ≤300 mg during the 30 days
prior to Baseline

- Willing and able to comply with all protocol-required procedures and
assessments/evaluations (e.g. willing to comply with opioid prescription lock
throughout the study, changes to the stimulation parameters, complete twice-daily
diary)

- 22 years of age or older when written informed consent is obtained

- Able to independently read and complete all questionnaires and assessments provided
in English

- Subject signed a valid, IRB-approved informed consent form (ICF) provided in English

Exclusion Criteria:

- Any pain-related diagnosis or medical/psychological condition that, in the
clinician's best judgment, might confound reporting of study outcomes (e.g. pelvic
pain, chronic migraine, schizophrenia)

- Current uncontrolled diabetes mellitus

- Significant cognitive impairment at Baseline that, in the opinion of the
Investigator, would reasonably be expected to impair the study candidate's ability to
assess pain intensity and/or complete a pain diary

- Participated in any investigational study within 30 days prior to the Screening Visit
or is currently participating in another clinical trial that may influence the data
that will be collected for this study

- A female who is breastfeeding or of child-bearing potential with a positive urine
pregnancy test or not using adequate contraception

- Plan to receive any massage or manipulation directly over the leads or by the
location of the IPG or treatments that involve sudden jerking motions of the torso at
any time during the course of the study

- Unresolved active litigation related to the pain condition being treated in the study

- Currently involved in a worker's compensation claim

- Unable to operate the SCS System