The placebo control arm used in the study is sham spinal cord stimulation (sham SCS). The device used to deliver sham SCS is the St. Jude Medical Invisible Trial System.

Pain-related disability was assessed using the six-item General Pain Disability Index (PDI) Questionnaire, which measures the degree to which chronic pain disrupts various aspects of daily life. Each item is rated on a 0-10 scale where 0 indicates no disability and 10 indicates total disability in that activity due to pain. The total score ranges from 0 to 60, with higher scores indicating greater pain-related disability. Change from baseline scores are calculated as the follow-up score minus the baseline score, where negative values indicate improvement (reduced pain-disability) and positive values indicate worsening (increased pain-related disability). Results were aggregated from all interventions regardless of treatment order and reflect the total difference from baseline.

The Brief Pain Inventory-Short Form (BPI-SF) assesses pain severity and pain interference with daily functioning. It includes four items assessing pain severity (worst, least, average, current) and seven items assessing interference (general activity, mood, walking, work, relations, sleep, enjoyment of life). Each item is rated 0 (no pain/interference) to 10 (worst pain/interferes completely). A total composite BPI-SF score was calculated by summing severity (range 0-40) and interference (range 0-70) domains for a total score of 0-110. Higher scores indicate greater pain burden and impairment. Change from baseline was calculated as follow-up score minus baseline score, where negative values indicate improvement. Results were aggregated from all interventions regardless of treatment order and reflect the total difference from baseline.

MBM was used to assess body areas where chronic pain was experienced and quantify the degree of widespread body pain (i.e. pain centralization). Pain spread was collected by having participants check all areas of the body as outlined on the body map where they felt persistent or recurrent pain. A checked box meant pain was present in that region of the body. The MBM had 35 boxes total participants could check, which were summed together to assess participants' pain. Lower number of checked boxes indicated less widespread pain; higher number of checked boxes indicated more widespread pain. Change from baseline scores are calculated as the follow-up score minus the baseline score, where negative values indicate improvement (reduced pain areas) and positive values indicate worsening (increased pain areas). Results were aggregated from all interventions regardless of treatment order and reflect the total difference from baseline.

Pain distribution was assessed using the Widespread Pain Index (WPI) component of the Fibromyalgia Survey Questionnaire (FSQ). The WPI is a 19-item checklist that evaluates the presence of pain or tenderness in specific body regions experienced during the past 7 days. Participants indicate whether they experienced pain in each of 19 anatomical areas including: bilateral shoulder, upper arm, lower arm, hip, upper leg, lower leg, and jaw; plus neck, upper back, lower back, chest, and abdomen. Each painful area receives a score of 1, with the total WPI score ranging from 0 to 19, where higher scores indicate more widespread pain distribution. Change from baseline scores are calculated as the follow-up score minus the baseline score, where negative values indicate improvement (reduced pain areas) and positive values indicate worsening (increased pain areas). Results were aggregated from all interventions regardless of treatment order and reflect the total diff

Symptom severity was assessed using the Symptom Severity Index component of the Fibromyalgia Survey Questionnaire (FSQ). The Symptom Severity Index evaluates fibromyalgia-related symptoms through two sections: (1) a three-item scale assessing fatigue, trouble thinking or remembering, and waking up tired over the past week, each rated on a 0-3 scale (0 = no problem, 1 = slight/mild, 2 = moderate, 3 = severe); and (2) a three-item checklist evaluating the presence of lower abdominal pain/cramps, depression, and headache over the past 6 months (0 = absent, 1 = present). The total Symptom Severity Index score ranges from 0 to 12, with higher scores indicating greater symptom severity. Change from baseline scores are calculated as the follow-up score minus the baseline score, where negative values indicate improvement and positive values indicate worsening. Results were aggregated from all interventions regardless of treatment order and reflect the total difference from baseline.

First, participants will receive sham (no) SCS. Study evaluations will be completed prior to and after this sham. Then, participants will have their stimulation adjusted to receive Burst-SCS. Study evaluations will be completed prior to and after stimulation.

Burst-SCS: The treatment arm used in the study is burst spinal cord stimulation (Burst-SCS). The device used to deliver Burst-SCS is the St. Jude Medical Invisible Trial System.

Sham SCS: The placebo control arm used in the study is sham spinal cord stimulation (sham SCS). The device used to deliver sham SCS is the St. Jude Medical Invisible Trial System.

Participants who were evaluated at baseline but did not undergo randomization. Un-randomized participants did not receive any SCS as part of the research study.

Total of all reporting groups

VAS was a horizontal line 100 millimeters (mm) in length with the word "no pain" and "worst possible pain" printed below. The participant marked on the line the point that they felt represented their perception of their current state. The score was determined by measuring in millimeters from the left hand with a total range of 0-100 millimeters, with a score between 0 (no pain) to a score of 100 (worst possible pain). Higher VAS values represented more severe pain and lower values represented lower pain.

SFMPQ was used to describe the quality of pain and had 15 descriptors (11 sensory and 4 affective). Each descriptor was scored by a 4-point intensity scale (0=none to 3=severe) (range 0-45). Pain scores were derived from the sum of the intensity rank values of the words chosen for sensory, affective, and total descriptors.

Pain-related disability was assessed using the six-item General Pain Disability Index Questionnaire, which measures the degree to which chronic pain disrupts various aspects of daily life. Each item is rated on a 0-10 scale where 0 indicates no disability and 10 indicates total disability in that activity due to pain. The total score ranges from 0 to 60, with higher scores indicating greater pain-related disability.

Pain severity and interference were assessed using the Brief Pain Inventory (BPI). The instrument includes four items measuring pain severity and seven items measuring pain interference with daily activities. Each item is rated on a 0-10 numerical rating scale. A total composite BPI-SF score was calculated by summing severity (range 0-40) and interference (range 0-70) domains for a total score of 0-110. Higher scores indicate greater pain burden and impairment.

MBM was used to assess body areas where chronic pain was experienced and quantify the degree of widespread body pain (i.e. pain centralization). Pain spread was collected by having participants check all areas of the body as outlined on the body map where they felt persistent or recurrent pain. A checked box meant pain was present in that region of the body. The MBM had 35 boxes total participants could check, which were summed together to assess participants' pain. Lower number of checked boxes indicated less widespread pain; higher number of checked boxes indicated more widespread pain.

Pain distribution was assessed using the Widespread Pain Index (WPI) component of the Fibromyalgia Survey Questionnaire (FSQ). The WPI is a 19-item checklist that evaluates the presence of pain or tenderness in 19 specific body regions. Each painful area receives a score of 1, with the total WPI score ranging from 0 to 19, where higher scores indicate more widespread pain distribution.

The Symptom Severity Index (SSI) component of the FSQ includes two sections: (1) a 3-item scale assessing fatigue, cognitive symptoms, and waking unrefreshed, each rated on a 0-3 scale (0=no problem, 1=mild, 2=moderate, 3=severe); and (2) a 3-item checklist evaluating the presence of lower abdominal pain, depression, and headache (0=absent, 1=present). Total scores range from 0 to 12, with higher scores indicating greater symptom severity.

The Short-Form McGill Pain Questionnaire (SFMPQ) assesses the quality and intensity of pain using 15 descriptors representing sensory (11 items) and affective (4 items) dimensions of pain. Each descriptor is rated on a 4-point intensity scale where 0=none, 1=mild, 2=moderate, and 3=severe. The total scores are calculated by summing the intensity ratings for each of the 15 descriptors (possible score range 0 to 45). Higher scores indicate more severe pain symptoms. Change from baseline scores are calculated as the follow-up score minus the baseline score, where negative values indicate improvement (reduced pain; better outcome) and positive values indicate worsening (increased pain; worse outcome). Results were aggregated from all interventions regardless of treatment order and reflect the total difference from baseline.

Of the 9 randomized participants, usable data was only obtained from 3 participants due to protocol deviations.

Pain-related disability was assessed using the six-item General Pain Disability Index (PDI) Questionnaire, which measures the degree to which chronic pain disrupts various aspects of daily life. Each item is rated on a 0-10 scale where 0 indicates no disability and 10 indicates total disability in that activity due to pain. The total score ranges from 0 to 60, with higher scores indicating greater pain-related disability. Change from baseline scores are calculated as the follow-up score minus the baseline score, where negative values indicate improvement (reduced pain-disability) and positive values indicate worsening (increased pain-related disability). Results were aggregated from all interventions regardless of treatment order and reflect the total difference from baseline.

Of the 9 randomized participants, usable data was only obtained from 3 participants due to protocol deviations.

The Brief Pain Inventory-Short Form (BPI-SF) assesses pain severity and pain interference with daily functioning. It includes four items assessing pain severity (worst, least, average, current) and seven items assessing interference (general activity, mood, walking, work, relations, sleep, enjoyment of life). Each item is rated 0 (no pain/interference) to 10 (worst pain/interferes completely). A total composite BPI-SF score was calculated by summing severity (range 0-40) and interference (range 0-70) domains for a total score of 0-110. Higher scores indicate greater pain burden and impairment. Change from baseline was calculated as follow-up score minus baseline score, where negative values indicate improvement. Results were aggregated from all interventions regardless of treatment order and reflect the total difference from baseline.

Of the 9 randomized participants, usable data was only obtained from 3 participants due to protocol deviations.

MBM was used to assess body areas where chronic pain was experienced and quantify the degree of widespread body pain (i.e. pain centralization). Pain spread was collected by having participants check all areas of the body as outlined on the body map where they felt persistent or recurrent pain. A checked box meant pain was present in that region of the body. The MBM had 35 boxes total participants could check, which were summed together to assess participants' pain. Lower number of checked boxes indicated less widespread pain; higher number of checked boxes indicated more widespread pain. Change from baseline scores are calculated as the follow-up score minus the baseline score, where negative values indicate improvement (reduced pain areas) and positive values indicate worsening (increased pain areas). Results were aggregated from all interventions regardless of treatment order and reflect the total difference from baseline.

Of the 9 randomized participants, usable data was only obtained from 3 participants due to protocol deviations.

Pain distribution was assessed using the Widespread Pain Index (WPI) component of the Fibromyalgia Survey Questionnaire (FSQ). The WPI is a 19-item checklist that evaluates the presence of pain or tenderness in specific body regions experienced during the past 7 days. Participants indicate whether they experienced pain in each of 19 anatomical areas including: bilateral shoulder, upper arm, lower arm, hip, upper leg, lower leg, and jaw; plus neck, upper back, lower back, chest, and abdomen. Each painful area receives a score of 1, with the total WPI score ranging from 0 to 19, where higher scores indicate more widespread pain distribution. Change from baseline scores are calculated as the follow-up score minus the baseline score, where negative values indicate improvement (reduced pain areas) and positive values indicate worsening (increased pain areas). Results were aggregated from all interventions regardless of treatment order and reflect the total diff

Of the 9 randomized participants, usable data was only obtained from 3 participants due to protocol deviations.

Symptom severity was assessed using the Symptom Severity Index component of the Fibromyalgia Survey Questionnaire (FSQ). The Symptom Severity Index evaluates fibromyalgia-related symptoms through two sections: (1) a three-item scale assessing fatigue, trouble thinking or remembering, and waking up tired over the past week, each rated on a 0-3 scale (0 = no problem, 1 = slight/mild, 2 = moderate, 3 = severe); and (2) a three-item checklist evaluating the presence of lower abdominal pain/cramps, depression, and headache over the past 6 months (0 = absent, 1 = present). The total Symptom Severity Index score ranges from 0 to 12, with higher scores indicating greater symptom severity. Change from baseline scores are calculated as the follow-up score minus the baseline score, where negative values indicate improvement and positive values indicate worsening. Results were aggregated from all interventions regardless of treatment order and reflect the total difference from baseline.

Of the 9 randomized participants, usable data was only obtained from 3 participants due to protocol deviations.

Participants in this group received sham spinal cord stimulation (Sham-SCS), a control condition in which the stimulation device was programmed but the output amplitude was set to 0 mA, so no electrical stimulation was delivered. This approach mimics device use without activating the therapeutic effect, serving as a placebo control for the study. The St. Jude Medical Invisible Trial System was used for all procedures. Study evaluations were conducted both before and after the intervention.