{"paper_id":"ccb08457-0699-41aa-9483-d79e72c1eec6","body_text":"Chronic pelvic pain (CPP) is a condition of heterogenous pain syndromes that affects up to 16% of men and women globally and takes a financial and emotional toll on patients, their families, and the healthcare system [ [1] ,  [2] ,  [3] ,  [4] ]. The American College of Obstetricians and Gynecologists (ACOG) defines CPP as pain lasting at least six months caused by pelvic organs or systems including gynecologic, urologic, gastrointestinal, musculoskeletal, neurologic, or psychiatric, of which the clinical manifestations lack clear identifiable causes [ 5 ]. While the pathophysiology of CPP is multifactorial and under active investigation [ 6 , 7 ], current theories posit a key role for central sensitization [ 5 , 8 ]. In support of this, patients commonly report neuropathic symptoms including paresthesias, hyperalgesia, and allodynia that interfere with activities of daily living and quality of life [ 9 , 10 ]. Neuropathic pain in CPP is typically managed with physical therapy, nerve blocks, medications ranging from anti-inflammatories to antidepressants and anticonvulsants, and surgical interventions. Despite this, many patients remain refractory to treatment.\nMore recently, neuromodulation via dorsal root ganglion (DRG) stimulation (DRGS) has been reported as an effective intervention for refractory CPP of various etiologies [ 11 ]. Compared to traditional spinal cord stimulation (SCS), which non-selectively targets passing fibers within the dorsal columns of the spinal cord, DRGS directly stimulates the DRG, a potential pain generator. More broadly, DRGS has been studied as a potential therapy for neuropathic chronic pain conditions such as complex regional pain syndrome, post-surgical pain, and peripheral neuropathy [ 12 ]. Some studies suggest that DRGS is an effective alternative to dorsal column SCS; in 60 patients who had chronic pain of various etiologies refractory to traditional SCS, DRGS was found to have a 90% trial-to-implantation rate, indicating responsiveness to DRGS among patients without sustained benefit from SCS [ 13 ]. Rowland et al. (2016) reported the first successful case of treatment with DRGS for CPP, in which DRG leads were implanted at L1 and L2 for a patient with severe pelvic girdle pain related to prior pregnancies [ 14 ]. This patient experienced functional improvements with sustained effect, demonstrating the potential of DRGS to ameliorate pelvic pain despite failure with more conservative therapies.\nFew studies have evaluated the efficacy of DRGS implants in CPP patients. Hunter et al. (2019) first published the results of a novel lead configuration of DRGS (leads placed at the bilateral L1 and S2 DRG) for the treatment of CPP [ 15 ]. In this retrospective case series of seven patients with CPP who underwent DRGS, all patients reported an improvement in pain, a reduction in opioid consumption, and in some cases, an improvement in sexual function and urination, with no explants reported at the one-year follow-up point [ 15 ]. Hunter et al. also demonstrated that the best predictor for successful pain relief from DRGS is the extent of paresthesia coverage of the painful area during programming of the DRGS [ 15 ]. Another case series of 15 patients, published by Patel et al. (2019), found that all 15 patients with CPP who underwent DRGS implant had improvement in function, symptoms, numeric rating scale (NRS) pain score, and modified Oswestry Disability Index (ODI) at the three-month follow-up point [ 16 ]. In one prospective cohort study, 55 patients with neuropathic CPP were identified, of which 11 underwent various types of neuromodulation, while the remaining 44 were medically managed [ 17 ]. The neuromodulation patients did not have a significant improvement in overall NRS, but did have improvement in other domains including worst NRS and pain catastrophizing scores [ 17 ]. While this study is not limited specifically to DRGS for CPP, it does demonstrate the utility of neuromodulation in this notoriously refractory condition [ 11 , 17 ]. Currently, the best predictor for successful pain relief from DRGS is the extent of paresthesia coverage of the painful area during programming of the DRG device [ 15 ]. However, little is known about other predictors for success or failure with DRGS in patients with CPP, or whether paresthesia stimulation may lead to benefits in a subgroup of patients.\nBased on the available evidence, DRGS appears to be a promising treatment modality for patients with refractory CPP. However, sample sizes and follow-up time intervals are limited, and there is a lack of information on the incidence of complications during the trial and/or implant period. Drawing from the SCS literature, despite its efficacy for several chronic pain conditions, this technology is associated with a relatively high rate of surgical revisions and explants, especially in the CPP population [ 18 ]. It logically follows that DRGS may have similar limitations, which makes the need for larger studies even more vital. DRGS has been studied in the treatment of chronic neuropathic pain in Denmark, where despite reported reductions in pain, the use of this technology was paused due to complications with maintaining and revising leads [ 19 ]. The risk of neurologic injury due to lead complications in the Danish study, in addition to high rates of lead fractures in other DRGS studies [ [20] ,  [21] ,  [22] ], prompted investigators to evaluate for improvements in procedural techniques, including an ipsilateral paramedian approach to minimize the risk of lead migration and fracture [ 23 ], as opposed to the traditional contralateral approach [ 19 ].\nThis study adds to the existing literature by reporting the outcomes of 31 patients with CPP-related diagnoses who underwent DRGS trial and/or implantation between 2017 and 2022 at two academic medical centers. Varying lead configurations were used based on patient pain distribution and inciting pathology. We report descriptive statistics, CPP histories and characteristics, and lead configurations chosen for trial and implant. We present the procedural logistics and functional response from the DRGS trial and permanent implant, if applicable. In addition, we provide information on the incidence of lead migration and fracture, revision surgery, reported side effects, and complications. We aim to compare our findings to those previously published, and describe patient- and/or systems-related issues and complications encountered throughout the process, in order to identify targets for future studies and quality and process improvement.\n\nThis study is a retrospective chart review of 31 patients who underwent a trial of DRGS for CPP of various etiologies between January 2017 and December 2022. The study protocol was approved by the Institutional Review Boards at Mass General Brigham (Protocol 2021P003703) and Tufts Medical Center/Lowell General Hospital (Protocol STUDY00003437) prior to patient enrollment. A Data Use Agreement (Number 2023A004230) was created to enable the sharing of data between the two institutions for the purposes of this study.\nPatients were selected based on the ACOG definition of CPP [ 5 ]. Diagnoses included pudendal neuralgia/neuropathy, coccygodynia, and/or other neuropathic-pain conditions in the pelvis. Inclusion criteria included patients presenting with at least six months of persistent, intractable pain affecting activities of daily living (ambulation, bowel and bladder function, dressing, hygiene, and transfers). The reported pain was refractory to conservative, pharmacologic, cognitive, behavioral, and interventional modalities. Failed multimodal regimens included pelvic floor therapy, physical therapy, alternative therapies (acupuncture, massage), oral medications (muscle relaxants, gabapentinoids, antidepressants, opioids, rectal or vaginal suppositories), interventional procedures (peripheral nerve blocks, onabotulinumtoxin A to the pelvic floor), or in less common cases surgical interventions (e.g. pudendal nerve decompression).\nPatients eligible for DRGS implantation underwent a 7–10 day DRGS trial with an FDA-approved system for DRGS (Proclaim DRG System, Abbott, USA) for CPP between January 2017 and December 2022 with a single provider within the Mass General Brigham System at Newton-Wellesley Hospital and two providers within the Tufts Medicine/Lowell General Hospital system. All procedures were performed by board-certified interventional pain management physicians with extensive experience in neuromodulation techniques. Trials were performed by Dr. Antje Barreveld (Newton-Wellesley Hospital, Newton, MA) and Drs. Alexandra Adler and Benjamin Henkle (Lowell General Hospital, Lowell, MA). Implantations were done between June 2018 and December 2022 by Dr. Robert Jason Yong (Brigham and Women's Hospital, Boston, MA) or Dr. Alexandra Adler (Lowell General Hospital). Pacific Interpreter Services was available to be utilized if needed.\nThe etiology of CPP was organized into three categories to encompass the diversity of medical diagnoses attributed to CPP: traumatic, surgical, or unknown (unspecified). Patients who were previously diagnosed with endometriosis were ultimately categorized under post-surgical CPP due to their history of prior surgical procedures with multiple co-existing diagnoses.\nThe DRGS trials were performed as outpatient procedures. Leads were placed percutaneously under fluoroscopic guidance at L1, S2 and/or S3 depending on each patient's pain distribution; this approach is based on previously published lead configurations and manufacturer recommendations [ 15 ]. The duration of the DRGS trial was 7–10 days. Following lead placement, an external pulse generator was connected to the leads and turned on to generate a paresthesia in the affected regions of pain. This process was repeated until the patient reported coverage of all painful regions. Patients who reported >50% improvement in pelvic pain intensity during the DRGS trial (which is the definition of a “successful trial” by the Centers for Medicare and Medicaid Services [ 24 ]) were offered DRGS implantation. Patients who did not report >50% improvement in pain intensity were not implanted.\nDRGS implantation was performed as an outpatient or day surgery procedure with percutaneous placement of leads under fluoroscopic guidance. Paresthesia mapping was performed depending on the preference of the implanting physician. The leads were tunneled and connected to an implantable pulse generator, which was then implanted subcutaneously. Programming of the system was performed by the manufacturer representative under the guidance of the implanting physician.\nRetrospective chart review utilizing the electronic medical record system (EPIC) enabled collection of demographic and clinical data for each patient. In addition to demographics, the following information was obtained from chart review: pain history (onset, location, duration, quality, severity, associated symptoms, alleviating/aggravating factors, radiation), comorbidities and pain-related diagnoses, previous interventions and responses, pre-and post-trial and/or implant pain scores if available, functional goals, trial details and reported percentage of pain relief, implant details for those who decided to pursue permanent DRGS implant, and any subsequent need for revision, re-operation or explantation.\nPatients without follow-up within the past year and/or missing information were contacted for a voluntary phone interview. Interviews were conducted after obtaining verbal consent and using an IRB-approved script, with the goal of assessing outcomes and better understanding patients’ experiences with the device. Follow-up survey data reflecting patient satisfaction with DRGS implantation was obtained using a five-point Likert Scale with the following options: “very dissatisfied”, “dissatisfied”, “neither satisfied or dissatisfied”, “satisfied”, and “very satisfied”. Patients had the option to express specific positive or negative feedback. Lastly, patients were asked to quantify how much overall percent pain relief they were receiving from the stimulator at the date of last follow-up.\nBoth quantitative and qualitative data analyses were performed. Quantitative data were analyzed using basic functions in Microsoft Excel and JMP (Version 16) and are presented in the form of means, standard deviation (SD) of the means, 95% confidence intervals (CI), frequencies, and distributions. 95% confidence intervals were calculated using the Modified Wald method. The distribution of lead configuration in both trials and implants were recorded. The percentage of patients with successful trials (defined as >50% relief of the target pain), patients with procedural issues related to the trial/implant, and those requiring revision surgery or explant are described. Furthermore, the consistency of lead configuration between trial and implant is reported. Qualitative reasons for explant, reported percent pain relief, and overall patient experience and feedback are summarized.\n\nA total of 31 patients with CPP underwent a 7–10 day DRGS trial between 2017 and 2022.  Table 1 ,  Table 2  present the demographic data, pain history, and DRGS trial details for all 31 patients. The mean age was 57.1 ± 14.3 years, and most patients were female (77%) and Caucasian (97%). Patients reported CPP of various etiologies with the most common etiology being post-surgical chronic pain (58%). Other causes included trauma (16%) or unknown causes (26%). The average pain duration prior to a DRGS trial was 11 ± 5 years ( Table 1 ). Twenty-one of 31 patients (67%) reported not being sexually active secondary to pain. Table 1 Patient demographics and pain history. Table 1 ID Age/Sex Race Pain Onset Duration (Years) Pain Description (Location, Quality, Associated Symptoms) 1 63/F Caucasian Traumatic vaginal delivery, worsened after subsequent hysterectomy with vaginal sling complicated by mesh erosion 35 Vaginal burning, foreign body sensation, urinary frequency, painful intercourse 2 53/F Caucasian Surgical, multiple vulvectomies for recurrent abscess formation 11 Vulvar left > right, perineal with radiation to left > right inner thigh, burning, allodynia, hyperesthesia, urinary frequency/incontinence, painful intercourse 3 37/F Caucasian Traumatic vaginal childbirth due to shoulder dystocia, vaginal laceration requiring re-repair 8 Left vaginal pain at introitus and internally throbbing, shooting, aching pain, painful intercourse 4 53/F Caucasian Cancer-related, started after radiation for anal cancer 8 Sacral pain near rectum, ischial bones, aching, burning, throbbing, dyschezia 5 70/F Caucasian Unknown (no inciting event) 12 Internal rectal, internal vaginal, burning, fullness, hot poker, painful intercourse 6 39/F Caucasian Surgical, worsened after hysterectomy 3 Rectal > vaginal, perineal pain, burning, urinary retention, painful intercourse 7 62/F Caucasian Injury/trauma, fractured sacrum after fall 7 Perianal, rectal, vulvar pain, dull, achy, burning, spasms, painful intercourse 8 57/F Caucasian Surgical, after hysterectomy with pelvic suspension and sling surgery 4 Right vagina, rectum, perineal, occasional vulva and inner groin pain, stabbing, burning, aching, urinary hesitancy, fecal incontinence, painful intercourse 9 47/F Caucasian Surgical, 2 months after vaginal hysterectomy 2 Right vagina radiating to groin/inner and anterior thigh, burning, sharp, shooting, allodynia, painful intercourse 10 83/M Caucasian Surgical, after bilateral inguinal hernia repair with mesh and transurethral prostate surgery 9 Right lower abdomen, groin, testicle, scrotum to penis, sharp, stabbing, allodynia, dysuria, painful intercourse 11 55/F Caucasian Surgical, after vulvectomy for cancer with multiple revision surgeries 7 Vulva, vagina, radiates to perineum, rectum, inner thigh, burning, stabbing 12 81/M Caucasian Cancer-related, after external beam radiation therapy for prostate cancer complicated by urethral stenosis 6 Entire penis > rectum, spasm, sharp, stabbing, shooting, fecal urgency and spasm, chronic urinary retention with suprapubic tube 13 56/F Caucasian Unknown (no inciting event) 21 Left rectum, ischial bone, gluteal region > vaginal pain, gnawing, throbbing, stabbing, allodynia, dyschezia, painful intercourse 14 34/F Caucasian Unknown (no inciting event), started with menses 16 Vaginal (internal and external), radiates to clitoris and suprapubic region, burning, allodynia, chronic urinary hesitancy, constipation, painful intercourse 15 58/F Caucasian Surgical, after ostomy reversal surgery complicated by infection 5 Rectal pain, burning, spasm, dyschezia, fecal urgency 16 54/F Caucasian Surgical, after myomectomy, then had hysterectomy which made pain worse 10 Left vaginal, labial, perineal, anal/rectal pain, can radiate to left posterior thigh, and suprapubic region, sharp, shooting, stabbing, dyschezia, constipation, painful intercourse, urinary hesitancy and retention 17 59/F Caucasian Unknown (no inciting event), possibly related to constant sitting 12 Vaginal, rectal, perineum, gluteal, stabbing, lightning bolt, squeezing, foreign body sensation, allodynia, urinary incontinence and frequency, painful intercourse 18 71/F Caucasian Surgical, after operation for bladder prolapse and hysterectomy 5 Rectum/anus left > right, internal vagina, left gluteal region, coccyx, sharp shooting, stabbing, saddle anesthesia, urinary frequency, dyschezia 19 75/F Caucasian Surgical, after hysterectomy 28 Vaginal, perineum, rectal, pressure, foreign body sensation, burning 20 41/F African American Unknown (no inciting event), worsened after abortion procedure 6 Deep pelvis bilaterally, suprapubic region, vagina, behind clitoris burning, soreness, cramping, pressure, painful intercourse, dysuria, urinary hesitancy 21 60/F Caucasian Surgical, after rectocele repair 8 Rectal right > left, coccyx, vagina, radiates to perineum, inner thigh, aching, burning, dyschezia 22 74/F Caucasian Injury/trauma, fall 17 Initially left vaginal, evolved to be more focused in rectum and coccyx, burning/hot, painful intercourse and intermittent bowel/bladder incontinence 23 53/F Caucasian Surgical, after L inguinal hernia repair with mesh, subsequent triple neurectomy and multiple mesh revisions 13 Left groin and vagina, sharp and burning 24 61/M Caucasian Surgical, after transurethral resection of the prostate 15 Rectal, perineal, buttock and inner thigh, burning, aching and sharp, urinary dysfunction 25 82/M Caucasian Prostatectomy 27 Left aspect of penis, burning and stabbing, urinary frequency (up to 10x per night) 26 36/F Caucasian Surgical, after total abdominal hysterectomy bilateral salpingectomy 7 Lower abdomen, pubic area and vagina, stabbing and sharp like “a bowling ball wrapped in barbed wire”, urinary urgency/frequency 27 65/M Caucasian Injury/trauma (fall) 9 Perineum, burning, urinary difficulties (leakage, incomplete voiding with overflow incontinence, has to self-catheterize) 28 56/M Caucasian Surgical, after R inguinal hernia repair 5 Right scrotum, intermittent burning 29 43/F Caucasian Injury/trauma, fall 6 Vaginal, clitoral and rectal, sharp and burning, urinary hesitancy/incontinence, dysfunctional defecation 30 64/F Caucasian Surgical, after hysterectomy 23 Vaginal and rectal, burning, aching 31 30/M Caucasian Unknown, no inciting event 12 Genital area and hips, aching, sharp, erectile dysfunction, slow voiding, post-void dribbling and pain worsened by bowel movements Table 1  summarizes the electronic medical record data reviewed for 31 patients who underwent a trial and/or DRGS implant at Newton-Wellesley Hospital, Brigham and Women's Hospital, or Lowell General Hospital between 2017 and 2022, including demographic information, pain onset, duration, and descriptors related to pain experience. Table 2 Summary of patient trial data. Table 2 ID Goals of DRGS Lead Configuration (number) Complications % Relief From Trial Patient goals met? Implanted (Yes/No) 1 Walk for 1 mile, resume sexual activity Bilateral L1/S2 (4) None 70 Yes, improvement in vaginal burning and able to walk at least 3 miles No: pain improved after trial; did not pursue implant 2 50% pain relief, sit for longer, work more hours, less pain with intercourse Left S2 (1) (insurance prohibited bilateral placement) Decreased relief due to S2 lead migration, skin reaction to adhesive 55 Yes, was able to sit for longer periods of time, >50% reduction in average pain score Yes 3 Less pain with sitting and intercourse Left L1/S2 (2) None 65 Yes, 100% relief of shock-like pain in introitus/perineum, 30–40% relief of pain with sitting/intercourse Yes 4 Decrease daily pain, sit for 20+ minutes Bilateral L1/S2 (4) None 80 Yes, 100% relief of burning pain when standing, 60% relief of sitting pain, able to sit longer Yes 5 Sit longer, decrease pain medications, less painful intercourse, bike ride, hike Bilateral L1/S2 (4) None 60 Yes, 100% relief of rectal pain, 65% relief of vaginal pain, decreased pain medications Yes 6 Be able to come off disability to work, be able to sit Bilateral S2/S3 (4) None 65 Yes, able to sit, be active for longer, less overall pain Yes 7 Return to work, less painful intercourse, sit longer Bilateral S2, left L1 (3) (unable to place Right L1 lead 2/2 discomfort) None 55 Yes, able to sit for longer, less painful intercourse Yes 8 Be able to bend over to do household chores, sit and drive further distances, go to the grocery store Right L1/S2 (2) Skin reaction to Chlorhexidine 60 Yes, able to sit, less pain with climbing stairs, walked without a cane, long walks, went to the grocery store Yes 9 More physical activity, walk longer, longer periods of household activities, walk up stairs alone Right L1/S2 (2) None 95 Yes, walked up stairs without assist, able to walk long distances without pain, sat and drove for 4 h Yes 10 50% pain relief, fewer or less intense pain flares, decrease pain medications, more physical activity Right T12/L1 (2) None 50 Yes, overall less pain flares and relief of abdominal and groin pain but no relief in testicle pain Yes 11 Less pain with activities around the house, be able to leave the house and drive, sit for 30 min Bilateral L1/S2 (4) Increased lower extremity and vulvar pain, even with reprogramming 0 No, felt increased pain, especially in lower extremities No 12 Reduce the intensity and frequency of spasms, less pain with bowel movements, decrease pain medications Left L1/S2 (2) None 0 No, no relief of rectal or penile pain No 13 Drive and sit for 35 min, be able to tolerate sitting during travel, wear underwear Left S2/S3 (2) None 0 No, no relief No 14 Resume physical workouts for conditioning, resume socialization and possibly dating Bilateral L1/S2 (4) None 60 Yes, less overall pain, fewer episodes of clitoral stimulation, able to participate in a workout Yes 15 Decrease pain with bowel movements, less rectal spasms and urgency, decrease pain medications, walk for longer Right S2/S3 (2) None 60 Yes, fewer bowel movements with less pain and spasm, able to double walking distance Yes 16 Decrease pain medications, less pain with intercourse Left L1/S2 (2) Migration of left S2 lead, but able to obtain adequate coverage with reprogramming 70 Yes, overall less pain, decreased pain medication, only remaining pain was deep vaginal pain Yes 17 Be able to go back to work, wear underwear, sit for longer Bilateral L1/S2 (4) Migration of right S2 lead, turned off during trial 0 No, felt no relief of rectal pain, had leg cramping and tingling in the groin with stimulation No 18 Be able to sit, resume gardening, increase walking distance, 50% reduction in pain Left S2/S3 (2) None 0 No, felt sitting was easier and less dyschezia on some days, but overall inconsistent during trial period and challenging to decide if it was helpful No 19 Be able to sit, increase socialization and volunteer work Bilateral L1/S2 (4) None 40 No, helped with burning pain but no relief of pressure or foreign body sensation No 20 50% reduction in pain, resume social activities, sit for 60 min, less painful intercourse Left L1/S2 (2) Procedural pain despite 10-day trial precluding evaluation 30 No, procedural pain throughout, did not want to extend trial period No 21 Sit for longer, 50% pain reduction, try to hike/kayak, leave the house Right L1/S2 (2) Increased pain, L1 lead turned off 60 Yes, was able to sit for longer and leave the house, most relief in vaginal and coccyx pain Yes 22 50% reduction in pain Left L1/S2 (2) Post-procedural pain, baseline pain worsened 0 No, vaginal/rectal burning was worse during the trial No 23 50% reduction in pain, sit for greater than 30 min Left L1/S2 (2) None 80 Yes, vaginal and groin pain were clinically improved Yes 24 50% reduction in pain, improve comfort with sitting, driving and volunteering Bilateral L1/S2 (4) None 70 Yes, able to sit longer Yes 25 50% reduction in pain, be able to sit and stand longer, less urinary frequency Left L1/S2 (2) Post-procedural pain >50 Yes, able to stand 45 min and cook, increased ability to socialize, able to reduce pain medication use by 50% Yes 26 50% reduction in pain, improve function and relationship with husband Bilateral L1 (2) None >50 Yes, relief of abdominal pain, no relief of “deeper bladder pain” Yes 27 50% reduction in pain, be able to ambulate Left S2, Right S3 (2) None 0 No pain relief or improvement in urinary symptoms, ambulation No 28 50% reduction in pain, Right L1/S2 (2) None 20 No pain relief No 29 50% reduction in pain, be able to sit longer and wear underwear Bilateral L1/S2 (4) None 80 Yes, able to sit >2 h, able to wear underwear Yes 30 50% reduction in pain, reduce pain with sitting Bilateral L1/S2 (4) S2 leads migrated after 3 days, patient lost some coverage and reprogrammed to optimize L1 leads 75 Yes, 60% relief of vaginal pain, 90% relief of rectal pain, able to sit more comfortably Yes 31 50% reduction in pain Bilateral L1/S2 (4) None 60 Yes, pain on the left was 75–80% improved, on the right it was 60% improved, daily function improved Yes Table 2  summarizes the data collected from 31 patients trialed with a DRGS, including subjective data related to goals of therapy and relief, as well as objective data regarding the trial such as lead configuration and the number of leads, complications, and whether the patient proceeded to an implant.\nPatient demographics and pain history.\nTable 1  summarizes the electronic medical record data reviewed for 31 patients who underwent a trial and/or DRGS implant at Newton-Wellesley Hospital, Brigham and Women's Hospital, or Lowell General Hospital between 2017 and 2022, including demographic information, pain onset, duration, and descriptors related to pain experience.\nSummary of patient trial data.\nTable 2  summarizes the data collected from 31 patients trialed with a DRGS, including subjective data related to goals of therapy and relief, as well as objective data regarding the trial such as lead configuration and the number of leads, complications, and whether the patient proceeded to an implant.\nAmongst patients with CPP caused by a surgical etiology, 14 out of 18 patients (78%, CI 54–92%) had a successful trial, as opposed to those with CPP caused by trauma (60%, CI 23–88%) or other causes (50%, CI 22–78%). Out of 31 patients, 29 had a pre-trial nerve block, most of which were pudendal nerve blocks, suggesting a diagnosis of pudendal neuralgia. Of the 29 who had a nerve block, 22 (76%, CI 58–88%) reported >50% reduction in pain for the duration of the local anesthetic.\nTrial:  The most common lead configurations utilized during DRGS trial were bilateral or unilateral L1 and S2 leads (21 out of 31 patients). Some notable exceptions are related to patient tolerance (ID Number 7) or insurance limitations (ID Number 2). The remaining lead configurations utilized for each patient's trial are presented in  Table 2 . Of the 31 patients who underwent DRGS trial, 21 patients (68%, CI 50–81%) reported >50% pain relief. Many patients had relief of some symptoms and not others, as reported in  Table 2 . There were patient, procedural, or systemic issues reported in 10 of the 31 patients during the trial period. Two patients experienced unanticipated skin reactions, one thought to be secondary to the adhesive and the other secondary to chlorhexidine. Four patients experienced lead migrations, all of which involved sacral leads. There was one insurance-related issue precluding bilateral lead placement during the trial period. Two patients experienced a worsening flare of chronic pain during and after the trial period, one patient had new groin pain resulting in one lead being turned off during the trial, and three patients reported severe procedural-related pain and could not assess pain relief during their DRGS trial ( Table 2 ).\nImplant : Twenty of the 21 patients with a successful DRGS trial underwent implantation, the details of which are presented in  Table 3 . One patient (ID Number 1) with a successful trial had improved pain relief persisting after the trial leads were removed, and therefore never pursued permanent implantation. A total of 68 individual leads were implanted. The average length of follow-up was 28.2 ± 17.3 months. Lead configurations used for permanent implant were the same as the trial configurations in the majority of patients (14 of 20 patients, 70%). Lead configurations were altered from the trial in six of the patients based on feedback and response to the trial. The most common lead configurations used for permanent implant were bilateral or unilateral leads placed at L1 and S2 (14 patients), with the remaining lead configurations utilized presented in  Table 3 . Table 3 Summary of patient implant data. Table 3 ID Lead Configuration (number) Revision required (number of revisions) Adverse Events Implant % Relief Able to Decrease Pain Medications? Still Implanted? Overall Satisfaction, General Impressions/Feedback Follow-Up (Months) 2 Bilateral L1/S2 (4) (trial was left S2) Yes (3) Lead migration, radiculitis 50 Yes Yes Functional goals met, satisfied, better quality of life, “Wasn't even living before and now I am,” continued bowel/bladder incontinence, urinary frequency, not MRI compatible 48 3 Left L1/S2 (2) (same as trial) Yes (1) Lead migration 40 Yes Yes Overall satisfied, able to sit longer, less painful intercourse 32 4 Bilateral L1/S2 (4) (same as trial) Yes (1) Nonfunctional lead due to high impedance 60 Yes Yes All functional goals met; very satisfied 48 5 Bilateral L1/S2 (4) (same as trial) Yes (1) Infection 75–80% initially Initially, not sustained No Initially 75–80% relief with goals met and decreased pain medications until revision surgery, never able to get good relief after with continued vaginal and rectal pain 48 6 Bilateral S2/S3 (4) (same as trial) No No 0 No No Developed worsening pain with stimulation, never got relief, persistent generator site pain 8 7 Bilateral S2/S3 (4) (trial was bilateral S2 + left L1; L1 not helpful) No No 60 Yes Yes Overall functional goals met, very satisfied 34 8 Right L1/S2, Left S2 (3) (trial was right L1/S2) No No 55 Yes Yes Reports implant process was more painful than anticipated, reports persistent sensitivity at generator site, feels it is helpful but not a cure, overall satisfied with continued functional improvement 20 9 Right L1/S2 (2) (same as trial) Yes (1) Implantable pulse generator pocket pain 95 Yes Yes Feels excellent relief and functional goals met, very satisfied, still with persistent discomfort at generator site 12 10 Bilateral T12/S2 (4) (trial was R T12/L1) Yes (1) Lead migration 50 No No 50% relief of abdomen/groin pain for about 6 months until left T12 lead migration, never got relief of testicular pain, S2 caused leg stiffness that did not resolve, ongoing soreness at generator site 5 14 Bilateral L1/S2 (4) (same as trial) No No 40 Yes No Initially got 50% improvement in low back pain and some relief of inner thigh pain but no vaginal/clitoral pain relief, symptoms of persistent genital arousal disorder worsened without relief, developed new leg stiffness and discomfort with stimulation, not MRI compatible 48 15 Bilateral S2/S3 (4) (trial was unilateral S2/S3) No No 80 Initially, not sustained Yes Very satisfied for ∼2 years, burning rectal pain returned after treatment for newly diagnosed genitourinary cancer, nonresponsive to reprogramming, now very dissatisfied 25 16 Left L1/S2 (2) (same as trial) No Lead migration and implantable pulse generator pocket pain, not revised 40 No No Not enough relief, overall disappointed, some relief for 2 months, then waning efficacy and lack of coverage of deep vaginal pain, lead migrations at L1 and S2, new lower extremity pain with stimulation, and persistent pain at generator site with migration of generator superficially, not MRI compatible 29 21 Bilateral L1 and right S2 (3) (trial was right L1 and S2) Yes (1) Lower extremity spasms and pain with stimulation and lack of rectal coverage, right S2 revised and S3 added 0 Yes No Never got relief, lack of rectal coverage, new lower extremity pain and spasm with stimulation, symptoms got worse after revision, explant complicated by lead breakage and inability to retrieve small lead fragment, later removed by neurosurgery as not MRI compatible 48 23 Left L1/S2 (2) (same as trial) No No 100 Yes Yes Very satisfied. “I would totally recommend it to anybody. It's worth everything. It changed my life.\" 7 24 Bilateral L1/S2 (4) (same as trial) No No lead migration or fracture, but worse pain in bilateral medial thighs, occasional stabbing pain in inner groin 50 No Yes Satisfied, can drive/sit for up to 2 h, can volunteer for a few hours, still sensitive to tighter underpants/clothes. 29 25 Left L1/S2 (2) (same as trial) No Occasional episodes of right penile pain 50 Initially, not sustained Yes Satisfied, he generally is “relatively pain free\" for 10–14 days. Then pain can flare for 5–6 days. Urinary frequency has decreased by >50% at nighttime. Standing and walking are still limited by pain. 4 26 Bilateral L1/S2 (4) (trial was bilateral L1) Yes (1) Lead fracture and migration 50 Yes Yes Very satisfied, functional goals met, “I would do the surgery every year if I had to.” 13 29 Bilateral L1/S2 (4) (same as trial) Yes (5) Lead fracture (multiple episodes) and migration, implantable pulse generator pocket pain 80–90% initially, now 30–50% No Yes Satisfied, was able to wear underwear and engage in sexual activity, however recent S2 lead fractures have disrupted pain relief 61 30 Bilateral L1/S2 (4) (same as trial) No Lead fracture of L1 (not revised) 65 Yes Yes Satisfied, good relief for 1 year, found to have fractured L1 lead, using remaining 3 leads with overall 65% relief 38 31 Bilateral L1/S2 (4) (same as trial) No Low back pain and loss of pelvic pain relief 50 No No Dissatisfied 7 Table 3  summarizes the data collected from 20 patients implanted with DRGS after trial, including subjective data related to overall satisfaction and feedback, as well as objective data such as lead configuration, revisions required, adverse events, and follow-up interval.\nSummary of patient implant data.\nTable 3  summarizes the data collected from 20 patients implanted with DRGS after trial, including subjective data related to overall satisfaction and feedback, as well as objective data such as lead configuration, revisions required, adverse events, and follow-up interval.\nThe most common adverse event was lead migration or fracture, which affected 7 out of 20 patients (35%) and 19 out of 68 leads (28%). Nine of the 20 implanted patients underwent revision surgery. Seven of these patients underwent one revision surgery, while two patients underwent three and five revision surgeries, for a total of 15 individual revision surgeries performed. The reasons for the revision surgeries included: lead fracture or migration (n = 9), persistent pain at the implantable pulse generator site (n = 2), lead exposure and infection (n = 1), a non-functional high-impedance lead of unknown etiology (n = 1), and unwanted side effects (either pain or spasm) secondary to stimulation at the planned location (n = 2) ( Table 3 ). Of note, some patients experienced adverse effects but did not undergo revision surgery including pain at the implantable pulse generator site (n = 1), lead migration (n = 1), and/or worse or new occasional pain (n = 3). From our 7 patients with lead migration and/or fracture, we calculated an average of 10.9 ± 14 months (range 0.5–36.1 months) to the first revision, generally widely distributed during the 28.2 ± 17.3 months follow-up.\nSeven of the 20 implanted patients ultimately had the device explanted, with an average time to explant of 12.5 ± 3 months. Two of these patients reported never getting relief after implantation (ID Numbers 6 and 21), whereas the other 5 patients reported some degree of partial relief initially (ID Numbers 5, 10, 14, 16, and 31). Reasons reported for explanation included the following: 1) lack of coverage of painful regions (ID Numbers 10, 14, and 16); 2) worsening pain or unwanted pain with the use of stimulation (ID Numbers 6, 10, 14, 16, and 21); and 3) persistent pain at the generator site (ID Numbers 6, 10, and 16). One patient's explant was complicated by a fracture in the S2 lead which precluded its retrieval, ultimately resulting in another operation (ID Number 21).\nThirteen of the 20 implanted patients remain implanted at the date of last follow-up, with an average overall reported percent relief of 55 ± 15%. Of our patients with DRGS still implanted, 92% report continued satisfaction: they are either “satisfied” (54%) or “very satisfied” (39%) with the DRGS results. Furthermore, our average length of follow-up was over two years (28.2 ± 17.3 months). Two of the 13 patients still implanted reported persistent pain at the generator site. Lastly, four of the 20 patients who underwent permanent implantation reported frustration about the device not being MRI-compatible.\n\nThe challenges of effectively treating CPP via emerging neuromodulation techniques are becoming increasingly clear. Such obstacles stem from the complexity of pelvic neuroanatomy, diagnostic uncertainty amongst patients with pelvic pain, and high rates of periprocedural complications. This retrospective chart review analyzes a sample of patients with CPP who were trialed with DRGS and subsequently implanted, and highlights the variable experiences of patients within domains such as relief, functionality, adverse events, and explantation in both the short- and longer-term. While ≥60% of our patients endorsed satisfaction with DRGS, some reported ineffective coverage of specific painful regions (clitoral, vaginal, testicular, and rectal pain), whereas others experienced unwanted stimulation to untargeted body parts (lower extremities and pelvis). This is not surprising given the innervation of the pelvis by both lumbar and sacral nerve roots.\nOverall, our study demonstrates that ≥60% of patients reported successful reduction in pain after both trial (68%, CI 50–81%) and implant (60%, CI 47–85%), which is consistent with most studies reporting favorable outcomes of >50% pain reduction [ 15 , 22 ]. The majority of implanted patients reported ongoing relief at the date of last follow-up, stating they are either “satisfied” or “very satisfied” with DRGS. Additionally, our study had more than a two-year follow-up on average, whereas many of the previous studies focus on outcomes less than one year after implantation [ 22 ]. While our study lacks statistical power to detect factors predicting successful trial or implant, we may compare our patient characteristics to those in studies powered sufficiently. Hunter et al. (2019) distributed an online questionnaire to chronic pain specialists across 14 institutions, including 217 patients trialed with DRGS for a broad range of diagnoses (including six patients with CPP), and identified several factors associated with DRGS trial success [ 15 ]. The most important predictor of trial success was percentage of coverage during the trial, with other predictors including the use of at least two leads during the trial, a pain description involving less than three dermatomes, a pre-existing nerve injury, and post-surgical pain [ 15 ]. Like Hunter et al. (2019), we did notice a relationship between patients with a presumed post-surgical etiology for pain and having a successful trial: 78% (CI 54–92%) of patients with a surgical etiology of their pain reported a successful trial, compared to those with trauma (60%, CI 23–88%) or other causes (50%, CI 22–78%) of pain. This suggests that the relationship between post-surgical pelvic pain and successful pain relief with DRGS should be studied further so as to improve patient selection for this technology.\nWhile our data demonstrate that patients are overall satisfied with their decision to pursue DRGS, approximately 32% of trialed patients and 70% of implanted patients experienced an adverse event. Such events ranged from a new pain complaint related to the device to lead fracture and/or migration, which affected 35% of implanted patients and 28% of implanted leads, respectively. These complications frequently resulted in at least one surgical revision. This rate of fracture and/or migration has been reported in other published studies [ 22 , 25 ]. Chapman et al. (2021) demonstrated that anchoring the DRGS leads significantly reduced lead migration but not fracture [ 22 ]. In our study, the use of anchors was not standardized, however, its utility in reducing complications warrants further investigation. Another recently reported approach is implantation via the paramedian, ipsilateral method for lead placement [ 26 ]. This approach involves parallel entry to the spinous process to facilitate lead placement and lateralization of the leads in the epidural space. Two small case studies concluded that the ipsilateral approach helps to avoid lead fracture from repetitive tension forces exerted from paraspinal muscle activation or entrapment within the fascial planes [ 21 , 27 ]. In the present study, a contralateral approach was used for both DRGS trial and implantation. Regardless, our ability to report on the rates of fracture and migration in 20 patients with more than two years of follow-up is an important contribution to the literature – it is likely applicable to all patients with DRGS and suggests the need not only for technical improvements but also for discussion of these unique risks during the consent process. Since lead migration and fracture are common complications of DRGS implantation frequently leading to reoperation [ 12 ], further large-scale studies are warranted in effort to reduce the financial and emotional implications of revision surgery.\nWhile this current study aims to provide procedural and outcome transparency and a characterization of factors related to the success or failure of DRGS, we acknowledge several notable limitations. First, this is a retrospective chart review, and as such there was no standardization of patient selection, pain diagnoses, lead configuration, or follow-up intervals. Furthermore, the outcome measures used in this study rely solely on subjective, patient-reported experiences in pain reduction and satisfaction with patients' individual functional goals, thus subjecting our data to recall bias. Given the retrospective nature of the study, we were unable to obtain all of the implanted patients' pre- and post- NRS scores, and therefore we lack detailed categorical data on pain outcomes in the implanted patients, and can only comment on each patient's reported percentage relief. While our retrospective data enables us to provide descriptive information regarding the patient experience with DRGS implant, we are unable to make nuanced conclusions on the efficacy of this technology for pain relief. Future prospective studies using validated outcome measures such as the Visual Analog Scale/NRS, ODI, Patient-Reported Outcomes Measurement Information System-29 (PROMIS-29), or Short Form Health Survey (SF-12) will greatly enhance the rigor and reliability of such data. Lastly, the small sample size and demographics of our patient population limit the generalizability of our results. While our patient population was recruited from both academic and private practice settings, larger, prospective randomized controlled trials or meta-analyses are needed to further determine optimal patient selection criteria and patient factors that predict success or failure of DRGS for CPP.\n\nThis study presents one of the largest samples of patients with CPP trialed with DRGS with an average of two years of follow-up. The results highlight the variable experiences of these patients after DRGS trial/implant and the need for individualized care. The patient experiences highlight the challenges of targeting CPP using neuromodulation given the complex neuroanatomy and innervation of the pelvis (summary data presented in  Table 4 ). While implanted patients experienced a 60% (CI 47–85%) success rate on average, we observed a high incidence of lead migration and fracture (35% of patients) and need for revision surgery (45% of patients). Perhaps more striking, given the frequency of migration and fracture, a total of 15 revision surgeries were performed on the 20 implanted patients and the explant rate was 35%, which is sparingly described in the literature. Table 4 Summary of outcomes for DRGS trials and implants. Table 4 Outcome Most common lead configuration for Trial and Implant Bilateral or unilateral L1/S2 Average % Pain Relief during Trial 48  ±  18% (n = 31) Average % Pain Relief for Implanted Patients 55  ±  15% (n = 20) Successful Trial (>50% relief) 68% (n = 31; CI 50–81%) Successful Implant (>50% relief) 60% (n = 20, CI 47–85%) Average Length of Follow-up for Implant 28.2  ±  17.3 months Patient/procedural/systematic issues during Trial 32% (n = 31) Patient/procedural/systematic issues during Implant 70% (n = 20) Adverse events requiring revision surgery for Implanted Patients 45% (n = 20) % Explanted 35% (n = 20) Average time to Explant 12.5 ± 3 months Table 4  presents summary outcome data from the 31 patients trialed and 20 patients implanted with DRGS.\nSummary of outcomes for DRGS trials and implants.\nTable 4  presents summary outcome data from the 31 patients trialed and 20 patients implanted with DRGS.\nDRGS may be an effective and life-changing therapy for patients suffering from CPP. However, the experience of our group and others demonstrate that patients implanted after a successful DRGS trial may experience waning pain relief over time, and potentially high rates of revision and/or explant. Patients should be counseled on the risk of DRGS complications involving lead migration or fracture and the potential need for revision surgery. Future studies should be performed to better understand which patients would most benefit from DRGS. Finally, studies to evaluate alternative techniques, such as the ipsilateral approach, are critical to help balance the benefit of this technology with current risks.\n\nThis research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.\n\nNo financial support to disclose.\n\nThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.","source_license":"CC0","license_restricted":false}