Paresthesia Free Spinal Cord Stimulation (PF-SCS)

The goal is to document efficacy of PF-SCS therapy in a blinded fashion and better understand how SCS therapy works in the clinical setting. Overall the investigators hope to improve patient care and selection of candidates who have the best potential for effective pain relief from an expensive and invasive therapy.

The PF-SCS has 3 programs (P1, P2, P3) that can be used. At Visit 1, the study physician will review the PF-SCS program that the participant has been using. This program is known as the optimal program (OPP) and will be known as P1. The study physician will then designate the other two programs (P2 and P3); one of them will be identical to the OPP (P1) and the other program will be the LAP. The participant will be unaware if the LAP is assigned to P2 or P3. At the end of Visit 1, the study physician will have the participant switch from P1 to the LAP (P2 or P3). The participant will be reassured that if their pain returns after they switch programs, they can immediately call the study physician and will be switched back to the previous OPP (P1) without delay. The participants whose pain returns will be categorized as Group 1. The physician will document the time that had elapsed before their pain returned. This time will be considered as "carry over time" (COT) from PF-SCS. Only the study physicians will be aware of the programming parameters for P2 and P3. The rest of the study staff and participants will be blinded and will not be aware of the programming parameters for P2 and P3.

The participants whose pain remains stable while on the LAP will be categorized as Group 2. All participants will keep a daily diary for pain intensity, sleep and any other concerns that may arise related to the change of program.

At the end of Visit 1, a member of the study team will schedule Visit 2, between 14 to 28 days from Visit 1.

Phone call: A study physician will call subjects between 7-14 days after Visit 1. Group 1 participants will be asked to switch to the LAP (P2 or P3) before Visit 2. To minimize the duration of the LAP, Visit 2 will be scheduled within six hours from the end of COT. The Group 2 participants will attend Visit 2 without changing their LAP.

At Visit 2, participants will fill out questionnaires on pain intensity, sleep, activities and global impression. A blinded study staff will perform QST on the subject. At the end of Visit 2, Group 1 participants will be instructed to go back to the OPP (P1). At the end of Visit 2, Group 2 will be allowed to switch back to the OPP (P1).

The investigators will use quantitative sensory testing (QST) as a tool to objectively quantify the impact of SCS on heat pain threshold, heat pain tolerance and wind-up over the painful area and compare this with a non-painful area in each subject. QST will be performed at Visit 1 and Visit 2.

Eligibility Criteria:
Inclusion Criteria:

* Subject will be 18-80 years old
* Subject who is currently treated with PF-SCS (HF-10 or Burst-mode capable SCS system) for chronic pain

Exclusion Criteria:

* Subject has neurological disease or a condition causing chronic persistent sensory deficit to the painful area
* Those receiving remuneration for their pain treatment (pending litigation or ongoing litigation).
* Those unable to read English and complete the assessment instruments.