ID# 1906671 Peripheral Nerve Stimulation for Chronic Post-Amputation Pain: A Literature Review

8551 Background: Comparison of cancer PS across settings is challenging due to differences in prognostic features. Data from 1 CCC participating in a multi-site international study of a pain classification system is presented to characterize cancer PS & response to PCC. Methods: The Edmonton Classification System for Cancer Pain was completed by prospective chart review to characterize PS of 100 consecutive hospitalized patients (pts) seen in PCC. Pts were followed until major PR, hospital discharge or death. Major PR was defined as <2 p.r.n. opioid doses/d & pain intensity (PI) <3/10 for 3 consecutive days (d). Results: 85% of pts had pain (n=85), with age 62.9+13.3, 47.1% male & KPS 44.5+23.1. The most common tumor diagnoses were lung (24.7%) & GU (21.2%). Pts were followed for a median of 4 d (0–27). 39% achieved a major PR. Except for steroids (49.4%) & anticonvulsants (29.4%), other adjuvant analgesic use was all <10%. Pain-associated features: *Numeric Rating Scale 0–10, 10=worst suggestivie of alcoholism + Mean morphine equivalent dailydose On univariate analysis, older age (p=.006), lower initial PI (p=.003), lower final PI (p=.001) & lower final MEDD (p=.002) were significantly associated with achieving major PR. On multivariate analysis, lower initial PI (p=.03) & lower final MEDD (p=.02) retained significance for achieving major PR. Conclusions: Only 39%of pts with cancer pain seen in PCC achieve a major PR by discharge or death. Despite aggressive opioid titration, 61% do not achieve a major PR & require better pain management. Potential strategies for achieving improved PR include earlier PCC, identification of more sensitive prognostic variables &critical evaluation of targeted therapies. [Table: see text] No significant financial relationships to disclose.

The future of therapeutic peripheral nerve stimulation for chronic pain

Introduction: Neuroendocrine studies have suggested that irregularities of the hypothalamic–pituitary–adrenal axis (HPA) play a causal role in the development and course of depression and chronic pain: Hypercortisolism has been associated with depression, low cortisol levels have been observed in some patients with chronic pain. However, little is known about the effects of experimentally-induced acute pain on cortisol secretion in patients with depression and chronic pain. Methods: We examined twenty-one patients with a major depression, twenty patients with chronic back pain and thirty-two healthy subjects were examined in an experimental pain paradigm. Pain intensity was rated by the participants with a visual-analog-scale. Salivary cortisol was assessed when the painful heat stimulus was applied and 45 and 60 minutes after the stimulus. We repeated the examination after 8 and 90 days. Results: We found no increase of salivary cortisol levels in the three groups after painful heat stimuli. Patients with chronic pain had lower cortisol AUC values compared to healthy controls and depressed patients at all time points (all p-values < 0.01). However, cortisol secretion in depressed patients did not differ from controls. Conclusions: Experimental heat pain stimuli did not elicit a significant cortisol response. The results confirmed the hypothesis that chronic pain is associated with hypocortisolism.

Chronic pain and major depression have been associated with alterations of the hypothalamus-pituitary-adrenal axis (HPA) activity. Previous studies suggested that HPA activity is diminished in chronic pain but increased in depression. However, little is known about the effects of experimentally induced acute pain on cortisol secretion in patients with chronic pain and depression. On three different occasions (day 1, day 8, day 90), we repeatedly examined 20 patients with chronic low back pain without depression, 22 patients with major depression without pain, and 33 healthy subjects using heat stimuli. Pain intensity was rated by participants using a visual analog scale. Salivary cortisol was assessed prior to 10 blocks of repeated painful heat stimuli, and 45 and 60 minutes afterwards. In repeated measures analyses of covariance adjusting for age, sex, and time of examination, we found a significant effect of group (P < 0.01) and post-hoc tests confirmed that patients with chronic pain had lower cortisol area-under-the-curve values compared with healthy controls and depressed patients at all time points (all P values <0.01). However, cortisol secretion in depressed patients did not differ from controls. Across groups, experimental heat pain stimuli did not elicit a significant cortisol response. Chronic pain appears to be associated with low cortisol secretion. The mechanisms linking chronic pain with low cortisol deserve further study.

Retrospective data review of positive disc injections at low pressures among subjects without chronic low back pain (LBP) illness compared to patients with chronic LBP undergoing Discography. To test the hypothesis that false-positive injections during Discography can effectively be eliminated by defining the positive injection criteria to include only those discs in which pain is produced with low injection pressure injections. The use of lumbar Discography as a diagnostic tool remains controversial. Studies have shown that disc injections among subjects asymptomatic of clinical LBP will produce painful injections in a significant proportion of subjects, rendering the interpretation of positive diskograms in clinical practice problematic. It has been argued that lumbar disc injections at low pressure may be clinically different from those at higher pressure and that a guideline accepting only of low-pressure injections will effectively eliminate false positives. A total of 69 volunteers with no clinically significant LBP undergoing experimental lumbar Discography were analyzed. There were 4 subgroups of this study cohort: no LBP, no chronic pain (n = 10); no LBP, chronic pain (n = 14); no LBP, previous lumbar discectomy (n = 20); and minor benign "backache" (n = 25). Pressure measurements during injection were made, and the pressure at which a significant pain response was elicited was recorded. This result was compared to the pain response and pressure profiles of 52 patients undergoing Discography for chronic LBP illness in consideration of treatment. Raters who were blinded to the subject's study group scored the studies. Diskogram morphology, pain response, and concordance, as well as magnetic resonance imaging, plain radiographs, psychometric testing (Distress and Risk Assessment Method), and compensation history were documented for each group. A low-pressure positive was defined as significant pain elicited less than 22 psi more than opening pressure. The number and percent of individuals with at least 1 low-pressure positive disc in the experimental group were 17 of 69 (25%) and in the clinical LBP group 14 of 52 (27%). The percentage of subjects with positive pain in the different experimental subgroups was: no LBP, no chronic pain 0/10 (0%); no LBP, chronic pain 5/14 (36%); no LBP, previous lumbar discectomy 5/20 (25%); and minor benign "backache" 7/25 (28%). Positive injections correlated with anular disruption, abnormal psychometric findings, and chronic pain states. The analysis shows that the rate of low-pressure painful injections in subjects without chronic LBP illness is approximately 25%, and correlates with both anatomic and psychosocial factors. In certain subgroups, this may represent an unacceptable risk of false-positive results.

Somatotosensory evoked potentials during baroreceptor stimulation in chronic low back pain patients and normal controls

Painful and nonpainful stimuli evoke distinct patterns of functional brain activity, particularly in secondary mechanical hyperalgesia and neuropathic pain-related structures. This meta-analysis aggregated the literature on the pattern of functional brain MRI and PET responses during these types of painful stimulation. PubMed and Web of Science database searches were used to find brain imaging responses to 4 different types of stimuli: nonpainful mechanical stimuli, painful mechanical stimuli, brush allodynia, and painful mechanical stimuli in a hyperalgesic zone. Our literature search encompassed 82 pain imaging studies published from 1999 to September 2023. The activation likelihood estimation technique was used to summarize the individual study results into meta-analytic statistical parametric maps. In healthy subjects, nonpainful mechanical stimuli primarily activated the left postcentral gyrus, bilateral precentral gyrus, and right insula while painful stimuli also recruited the bilateral cingulate gyrus. Participants with chronic pain showed similar activation patterns. However, contrasts between chronic pain patients and healthy participants revealed greater activation of the left cingulate gyrus and right insula. Brush allodynia and hyperalgesic stimuli also activated these brain regions in both healthy subjects and chronic pain patients to a lesser extent. These results further our knowledge of the neuronal networks underlying the complex experience of pain across the entirety of the human brain. We discuss the limitations of the literature, particularly the paucity of research in neural correlates of brush allodynia and mechanical hyperalgesia, and how these deficits may be addressed.

Physical injury, including surgery, can result in chronic pain; yet chronic pain following childbirth, including cesarean delivery in women, is rare. The mechanisms involved in this protection by pregnancy or delivery have not been explored. We examined the effect of pregnancy and delivery on hypersensitivity to mechanical stimuli of the rat hindpaw induced by peripheral nerve injury (spinal nerve ligation) and after intrathecal oxytocin, atosiban, and naloxone. Additionally, oxytocin concentration in lumbar spinal cerebrospinal fluid was determined. Spinal nerve ligation performed at mid-pregnancy resulted in similar hypersensitivity to nonpregnant controls, but hypersensitivity partially resolved beginning after delivery. Removal of pups after delivery prevented this partial resolution. Cerebrospinal fluid concentrations of oxytocin were greater in normal postpartum rats prior to weaning. To examine the effect of injury at the time of delivery rather than during pregnancy, spinal nerve ligation was performed within 24 h of delivery. This resulted in acute hypersensitivity that partially resolved over the next 2-3 weeks. Weaning of pups resulted only in a temporary return of hypersensitivity. Intrathecal oxytocin effectively reversed the hypersensitivity following separation of the pups. Postpartum resolution of hypersensitivity was transiently abolished by intrathecal injection of the oxytocin receptor antagonist, atosiban. These results suggest that the postpartum period rather than pregnancy protects against chronic hypersensitivity from peripheral nerve injury and that this protection may reflect sustained oxytocin signaling in the central nervous system during this period.

What’s New in the Management of Pain in Children

Novel minimally invasive short-term and long-term peripheral nerve stimulation (PNS) systems have revolutionized targeted treatment of chronic neuropathic pain. We present an international survey of PNS-implanting pain physicians to assess what factors they consider when offering permanent PNS. This cross-sectional study consisted of a survey (Qualtrics) that was distributed to PNS-implanting physicians in a device supplier's entire email database on November 13, 2020, with 3weeks of response time. Physicians' contact information in the form of their email addresses had been previously collected by the supplier upon device distribution with permission to use survey responses for research. Of 2032 database physicians, 40 physicians representing 37 institutions responded to the survey. The most common application of PNS was mononeuropathic pain (57%). The most frequently targeted nerve was the suprascapular nerve (29%). 14% of physicians reported 81-100% of their implants were dual-lead. The representative physicians ranged broadly in their most frequently targeted nerves. Although mononeuropathic pain was the most common indication for PNS, there was still varied response regarding other indications such as CRPS and post-surgical chronic pain. In context of a low response rate, identifying such factors can help update the prevailing treatment algorithm for interventional therapies, assist pain physicians in better identifying which patients are the best candidates for PNS, and inform future clinical trial design on PNS efficacy.

BackgroundChronic low back pain (CLBP) is a common and debilitating condition often difficult to diagnose, with entrapment of the superior cluneal nerves (SCN) being a overlooked cause. Cluneal neuralgia (CN) arises from injury to the SCN and can significantly impact patients' quality of life.ObjectivesThis case series aims to evaluate the effectiveness of the Micro Lead - SPRINT Peripheral Nerve Stimulation (PNS) System, (Cleveland, Ohio, USA) for treating cluneal neuralgia, utilizing both fluoroscopic and ultrasound guidance for accurate nerve localization.MethodsA retrospective review was conducted on six nonconsecutive patients who underwent Micro Lead - SPRINT Peripheral Nerve Stimulation (PNS) System, (Cleveland, Ohio, USA) implantation for cluneal nerve entrapment at MetroHealth System between August 2021 and January 2024. Patient selection focused on individuals with cluneal neuralgia refractory to conservative treatments. Data collection included demographics, pain characteristics, opioid usage, and follow-up evaluations at 30, 60, 90 days, and 2 years post-procedure. Outcomes were assessed using the Numerical Rating Scale (NRS) for pain. Dividing the NRS score by the maximum score (10) and multiplying by 100 expresses pain intensity as a percentage.ResultsAmong the six nonconsecutive patients (83 % female, mean age 60 years), the mean pain score prior to implantation was 7.1. At follow-up, five patients reported over 50 % improvement in pain and functional status. Three patients with prior opioid use had varying outcomes regarding opioid consumption post-procedure.ConclusionThe Micro Lead - SPRINT Peripheral Nerve Stimulation (PNS) System, (Cleveland, Ohio, USA) demonstrates promise as an effective treatment for cluneal neuralgia, leading to reductions in pain and improvements in daily living activities. Further studies are warranted to validate these findings.

ESRA19-0696 Non-pharmacological methods for comfort and pain management (virtual reality, musicotherapy, hypnosis,……)

A life switch in pain

Background: Peripheral nerve stimulators (PNS) are an option when medications, injections, physical therapy, and transcutaneous electrical stimulation are not effective. Rotator cuff muscle disorders and acromioclavicular or glenohumeral joint pathologies commonly lead to chronic shoulder pain. However, this case report documents a PNS treating chronic shoulder pain following traumatic humeral fracture. Case Report: Our patient presented years after her orthopedic team recommended nonoperative management for her traumatic humeral fracture. She described pain at rest (3-5/10), which was exacerbated by forward flexion and abduction (9/10). After her PNS, she noted greater than 80% pain relief (rating it a 3/10), as well as improved range of motion and improved pain with movement, 4/10 with movement. Conclusion: This case is the first report of PNS use for traumatic humeral fracture, when the patient’s clinical status precluded operative intervention. Our patient reported satisfaction with her pain relief and improved range of motion. Key words: Peripheral nerve stimulation (PNS), neuromodulation, interventional pain, chronic shoulder pain, shoulder pain, chronic pain, humeral fracture, trauma

Chronic pain is one of the most prevalent health problems in the world today, yet neurological markers, critical to diagnosis of chronic pain, are still largely unknown. The ability to objectively identify individuals with chronic pain using functional magnetic resonance imaging (fMRI) data is important for the advancement of diagnosis, treatment, and theoretical knowledge of brain processes associated with chronic pain. The purpose of our research is to investigate specific neurological markers that could be used to diagnose individuals experiencing chronic pain by using multivariate pattern analysis with fMRI data. We hypothesize that individuals with chronic pain have different patterns of brain activity in response to induced pain. This pattern can be used to classify the presence or absence of chronic pain. The fMRI experiment consisted of alternating 14 seconds of painful electric stimulation (applied to the lower back) with 14 seconds of rest. We analyzed contrast fMRI images in stimulation versus rest in pain-related brain regions to distinguish between the groups of participants: 1) chronic pain and 2) normal controls. We employed supervised machine learning techniques, specifically sparse logistic regression, to train a classifier based on these contrast images using a leave-one-out cross-validation procedure. We correctly classified 92.3% of the chronic pain group (N = 13) and 92.3% of the normal control group (N = 13) by recognizing multivariate patterns of activity in the somatosensory and inferior parietal cortex. This technique demonstrates that differences in the pattern of brain activity to induced pain can be used as a neurological marker to distinguish between individuals with and without chronic pain. Medical, legal and business professionals have recognized the importance of this research topic and of developing objective measures of chronic pain. This method of data analysis was very successful in correctly classifying each of the two groups.