BACKGROUND:In 2021, the term persistent spinal pain syndrome (PSPS) was introduced. PSPS type 2 (PSPS-T2) replaced the unsatisfactory term failed back surgery syndrome (FBSS). PSPS type 1 (PSPS-T1) is a clinical picture of signs and symptoms of FBSS but without prior surgery. PSPS applies to any spinal level. There are multiple underlying mechanisms and treatments within PSPS. Therapeutic choices are not based on a common nomenclature. One consequence is that the desired outcomes of interventions are not reliably achieved. There is a need to redefine diagnostic clusters of PSPS based on the pain mechanism rather than just anatomic factors or a history of previous surgery. This manuscript provides mechanism-based recommendations to improve treatment selection through the use of the PSPS concept. METHODS:An international task force of pain and neurosurgical specialists was established and met at the International Neuromodulation Society Congress 2024, at the North American Neuromodulation Society Congress 2024, and online. RESULTS:An overview of classification systems (i.e., PSPS; P), anatomical structure (A), neural mechanism (M), and degree of certainty (C), is discussed and combined to generate a novel categorization approach to assist with PSPS classification and diagnosis. The PAMC scale was developed to assist with the diagnosis clustering and consequently to improve treatment selection. CONCLUSION:The proposed recommendations should support future research by better defining study populations and by assisting the clinician to select the appropriate therapy.

Russo, Marc A.a,*; Visser, Ericb; North, Richard B.c; Stanton-Hicks, Michaeld; Georgius, Petere; Volschenk, Willema; Santarelli, Danielle M.f Author Information

Failed back surgery syndrome (FBSS) is a stigmatizing and misleading term, and in many cases surgery is not relevant to the development, persistence, worsening or recurrence of the symptoms. An international panel recently proposed the notion of Persistent spinal pain syndrome (PSPS) as the preferred option to replace FBSS. The new label avoids ambiguity and inappropriately-implied causation. PSPS type 1 applies when there was no spinal surgery; type 2 applies when surgery had occurred. PSPS is therefore broader than FBSS but more accurate.

Flawed nomenclature and classification inevitably hamper diagnosis, clinical communication and research, and may impede access to appropriate treatment. This is clearly illustrated by the term ‘failed back surgery syndrome’ (FBSS), which is particularly misleading and inadequate, and carries unintended negative connotations. We represent an independent international group of 25 experts in the clinical and scientific aspects of chronic pain of spinal origin who seek support for the aim of discontinuing use of the term FBSS, and for its replacement. FBSS (and FNSS: ‘failed neck surgery syndrome’) fails to indicate whether surgery caused or exacerbated the pain directly, or indirectly, or simply failed to relieve the pain, and it is unclear about recurrent pain. It identifies neither inappropriately-performed surgery, for example insufficient decompression and unjustified intervention, nor the effects of complications of surgery, such as neurological damage. There is no reference to pathophysiological mechanisms nor, even, to the particular operation(s) performed. Psychological and social factors are ignored, despite their frequent relevance, but the juxtaposition of ‘failed’ and ‘syndrome’ can imply that the patient is to blame. The therapeutic nihilism infers a poor prognosis. Finally, successful back surgery is not clearly defined, so there is no point of reference. Following a three-year process of literature review, extensive discussion and a structured Delphi selection procedure, we propose that the term ‘persistent spinal pain syndrome’ (PSPS) be adopted. This term is based on the principle of a persistent spinal syndrome and includes, but is not restricted to, post-surgical pain. Its logical basis should facilitate the diagnosis and therapy of individual patients in a manner that is physiologically orientated and not emotionally laden, ambiguous or stigmatising. The latest version of the International Classification of Diseases, ICD-11, was adopted by the WHO in 2019 and is due for international implementation in January, 2022. Within this, chronic pain is recognised as a disease entity for the first time. ICD-11 proposes the term ‘chronic pain after spinal surgery’ (CPSS) and, to avoid ambiguity, defines it narrowly as ‘pain caused by, or probably caused by, surgery’. Thus, cases where the pain persisted after surgery but was not caused by it, i.e. the majority, are excluded from CPSS. Furthermore, cases where surgery was not performed may be otherwise indistinguishable from cases where it was. PSPS takes a different approach, by starting from the broad concept that the upright posture predisposes humans both to the development of pain of spinal origin, and related symptoms, and to their persistence. This predisposition may militate against favourable surgical outcomes. It refers to persistent pain of spinal origin, with or without associated neurological symptoms, axial, radicular or mixed, and does not apply exclusively to the lumbar spine. In PSPS type 2, spinal surgery occurred which may be directly causative, indirectly causative, not causative, or unclear. It incorporates CPSS as a subgroup but is not restricted to it. Type 1 is where no spinal surgery was performed and symptoms persist despite optimal nonsurgical management. Chronic primary pain is excluded from PSPS as it is not specifically of spinal origin. Under ICD-11, cases currently labelled FBSS will be distributed between four first-level diagnostic categories. The integration of PSPS into ICD-11 would rationalise this, partly by making use of the novel ICD-11 tool ‘shared parents’. Ambiguity regarding causation would be avoided, and the commonality of cases where surgery was causally irrelevant, or did not even occur, would be recognised. The terms FBSS and FNSS need no longer be used if PSPS is adopted; we urge authors and editors to help drive this process.

INTRODUCTION:Complex regional pain syndrome (CRPS), formerly known as reflex sympathetic dystrophy (RSD), is a difficult to treat condition characterized by debilitating pain and limitations in functional ability. Neuromodulation, in the form of spinal cord stimulation (SCS) and peripheral nerve stimulation (PNS), have been traditionally used as a treatment for CRPS with variable success.OBJECTIVE:This chart review describes the use of implantable PNS systems in the treatment of CRPS of the upper and lower extremities spanning nearly three decades.MATERIALS AND METHODS:A retrospective chart review was performed on 240 patients with PNS implanted between 1990 and 2017 at our institution. Of these, 165 patients were identified who had PNS systems implanted for a diagnosis of CRPS. Patient profile, including baseline characteristics, comorbidities, past/current interventions/medications and targeted nerves, was descriptively summarized through standard summary statistics. Patients' pain scores and opioid consumptions at baseline (preimplant), 1 month, 6 months, and 12 months were collected and compared. Device revisions and explants were summarized, and patient functional outcomes were described.RESULTS:Pain scores at baseline and at 12-month follow-up were decreased from a mean of 7.4 ± 1.6 to 5.5 ± 2.4 and estimated to be 1.87 (95% CI: [1.29, 2.46], paired t-test p-value <0.001) lower at 12 months. At baseline, 62% of patients were on chronic opioid therapy, compared with 41% at 12 months. Of 126 patients who reported changes in functional status, 64 (51%) reported improvement, 27 (21%) reported worsening, and 35 (28%) did not report any meaningful change. Excluding end-of-life battery replacements, surgical revision occurred in 56 (34%) of patients. Thirteen patients (8%) underwent implantation of a second PNS because of symptomatic expansion outside of the original painful region. Device explant was performed in 32 (19%) of patients. Median length of follow-up was 74 [14, 147] months. Of the 36 patients who continue to follow-up at our institution, 29 (81%) continue to use their PNS.CONCLUSIONS:We can conclude that PNS is a useful modality to improve function and reduce long-term pain in selected patients suffering from CRPS type I and type II.

This chapter turns to the history of the beginnings of the societies that are important to the founding of a medically relevant paradigm, in this instance, neuromodulation. The International Neuromodulation Society (INS) was founded as an offshoot of the World Society of Functional and Stereotactic Neurosurgery (WSSFN), a society of neurosurgeons most interested in stereotactic surgery for cancer and functional neurosurgery, and Dr. Konstantin Slavin, past president of the American Society of Functional and Stereotactic Neurosurgery and secretary-treasurer of the WSSFN, will discuss the founding and beginnings of this society, followed by perspectives on the founding and beginnings of the INS by two of its past presidents, Dr. Giancarlo Barolat of the United States and Mr. Brian Simpson of Wales in the United Kingdom. Finally, because of its importance to the INS (largest and first INS chapter), I have asked Dr. Michael Stanton-Hicks to reminisce on the beginnings North American Neuromodulation Society.

Sensory disturbances often spread beyond the site of injury in complex regional pain syndrome (CRPS) but whether this applies equally to CRPS I and II, or changes across the course of the disease, is unknown. Establishing this is important, because different symptom profiles in CRPS I and II, or in acute vs chronic CRPS, might infer different pathophysiology and treatment approaches. To explore these questions, sensory disturbances were assessed in the limbs and forehead of 71 patients with CRPS I and 33 patients with CRPS II. Pain had persisted up to 12 months in 32 patients, for 13 to 36 months in 29 patients, and for longer than this in 43 patients. Patients with CRPS I were more likely to be female, and pain was more likely to be present in an additional limb, than patients with CRPS II. Conversely, pain was more likely to be associated with sensory deficits and allodynia in patients with CRPS II than CRPS I. Nevertheless, heightened sensitivity, allodynia, and/or hyperalgesia to mechanical and thermal stimuli were detected in a hemisensory distribution ipsilateral to the affected limb in both forms of CRPS. Some of these hemisensory disturbances strengthened with chronicity of pain. These findings suggest that heightened excitability of nociceptive pathways in CRPS spreads to hemisensory convergence points in the brainstem or higher brain centres, possibly in association with compromised pain controls. The similarity of symptom profiles in chronic CRPS I and II implies shared mechanisms despite different triggers.

Clinical diagnosis of complex regional pain syndrome (CRPS) is a dichotomous (yes/no) categorization, a format necessary for clinical decision making. Such dichotomous diagnostic categories do not convey an individual's subtle gradations in the severity of the condition over time and have poor statistical power when used as an outcome measure in research. This prospective, international, multicenter study slightly modified and further evaluated the validity of the CRPS Severity Score (CSS), a continuous index of CRPS severity. Using a prospective design, medical evaluations were conducted in 156 patients with CRPS to compare changes over time in CSS scores between patients initiating a new treatment program and patients on stable treatment regimens. New vs stable categorizations were supported by greater changes in pain and function in the former. Results indicated that CSS values in the stable CRPS treatment group exhibited much less change over time relative to the new treatment group, with intraclass correlations nearly twice as large in the former. A calculated smallest real difference value revealed that a change in the CSS of ≥4.9 scale points would indicate real differences in CRPS symptomatology (with 95% confidence). Across groups, larger changes in CRPS features on the CSS over time were associated in the expected direction with greater changes in pain intensity, fatigue, social functioning, ability to engage in physical roles, and general well-being. The overall pattern of findings further supports the validity of the CSS as a measure of CRPS severity and suggests it may prove useful in clinical monitoring and outcomes research.

Limited research suggests that there may be Warm complex regional pain syndrome (CRPS) and Cold CRPS subtypes, with inflammatory mechanisms contributing most strongly to the former. This study for the first time used an unbiased statistical pattern recognition technique to evaluate whether distinct Warm vs Cold CRPS subtypes can be discerned in the clinical population. An international, multisite study was conducted using standardized procedures to evaluate signs and symptoms in 152 patients with clinical CRPS at baseline, with 3-month follow-up evaluations in 112 of these patients. Two-step cluster analysis using automated cluster selection identified a 2-cluster solution as optimal. Results revealed a Warm CRPS patient cluster characterized by a warm, red, edematous, and sweaty extremity and a Cold CRPS patient cluster characterized by a cold, blue, and less edematous extremity. Median pain duration was significantly (P < 0.001) shorter in the Warm CRPS (4.7 months) than in the Cold CRPS subtype (20 months), with pain intensity comparable. A derived total inflammatory score was significantly (P < 0.001) elevated in the Warm CRPS group (compared with Cold CRPS) at baseline but diminished significantly (P < 0.001) over the follow-up period, whereas this score did not diminish in the Cold CRPS group (time × subtype interaction: P < 0.001). Results support the existence of a Warm CRPS subtype common in patients with acute (<6 months) CRPS and a relatively distinct Cold CRPS subtype most common in chronic CRPS. The pattern of clinical features suggests that inflammatory mechanisms contribute most prominently to the Warm CRPS subtype but that these mechanisms diminish substantially during the first year postinjury.

INTRODUCTION:The Neuromodulation Appropriateness Consensus Committee (NACC) of the International Neuromodulation Society (INS) evaluated evidence regarding the safety and efficacy of neurostimulation to treat chronic pain, chronic critical limb ischemia, and refractory angina and recommended appropriate clinical applications.METHODS:The NACC used literature reviews, expert opinion, clinical experience, and individual research. Authors consulted the Practice Parameters for the Use of Spinal Cord Stimulation in the Treatment of Neuropathic Pain (2006), systematic reviews (1984 to 2013), and prospective and randomized controlled trials (2005 to 2013) identified through PubMed, EMBASE, and Google Scholar.RESULTS:Neurostimulation is relatively safe because of its minimally invasive and reversible characteristics. Comparison with medical management is difficult, as patients considered for neurostimulation have failed conservative management. Unlike alternative therapies, neurostimulation is not associated with medication-related side effects and has enduring effect. Device-related complications are not uncommon; however, the incidence is becoming less frequent as technology progresses and surgical skills improve. Randomized controlled studies support the efficacy of spinal cord stimulation in treating failed back surgery syndrome and complex regional pain syndrome. Similar studies of neurostimulation for peripheral neuropathic pain, postamputation pain, postherpetic neuralgia, and other causes of nerve injury are needed. International guidelines recommend spinal cord stimulation to treat refractory angina; other indications, such as congestive heart failure, are being investigated.CONCLUSIONS:Appropriate neurostimulation is safe and effective in some chronic pain conditions. Technological refinements and clinical evidence will continue to expand its use. The NACC seeks to facilitate the efficacy and safety of neurostimulation.

ObjectivesElectrical peripheral nerve stimulation (PNS) is discussed as an effective neuromodulatory treatment in chronic pain. This human experimental study hypothesized a rightward shift of stimulus-response function as a marker of antinociceptive and analgesic PNS effects.Materials and MethodsInnocuous electrical PNS of the left superficial radial nerve trunk evoked paresthesia on the left hand dorsum in 29 healthy volunteers. In this innervation area, laser stimulation was performed before, during, and after PNS. Ten different laser intensities ranging between perception and tolerance thresholds were applied. Cortical laser-evoked potentials (LEP) were recorded, and perceptual ratings were documented. Data were analyzed in low, medium, and high laser intensity categories. Stimulus-response functions were calculated. Laser detection and pain thresholds were interpolated.ResultsInterpolated laser thresholds after logarithmic regression were not different from measured thresholds. Laser pain threshold increased during and after PNS. LEP amplitude decreased at medium and high intensities under PNS. Ratings transiently decreased during PNS at medium and high laser intensities.ConclusionsModulation of laser pain threshold, perceptual ratings, and LEP indicates a rightward shift of stimulus-response function under PNS. These data emphasize antinociceptive and analgesic effects of PNS in an experimental human model and support its clinical neuromodulative relevance.

ObjectiveAn international panel of pain specialists (anesthesiology, neurology, neurosurgery, and psychology) and research methodologists developed a screening tool to identify patients who may be suitable for spinal cord stimulation (SCS)the Refractory Chronic Pain Screening Tool (RCPST) prototype. We describe a feasibility study to explore practicality and validity of this prototype.DesignConsecutive outpatients were screened in two centers (United Kingdom and United States). Sixty chronic pain adults without satisfactory pain relief despite treatment were assessed using RCPST (by pain specialist without expertise in neurostimulation) and then evaluated by two pain specialists experienced in SCS implantation and management to determine whether the patient should be referred for SCS. To maintain blinding, the participating physicians did not inform each other or the patient of assessment outcome. Sensitivity and specificity of the RCPST prototype were calculated using implanters' judgment as gold standard.ResultsThe average age of patients was 47.7 years; 53% were female. Fifty-seven patients completed the study (one withdrew consent, two lost to follow-up). The pain specialists agreed the prototype was easy to use and took <10 minutes to complete. Implanter agreement was moderate (Kappa: 0.63, 95% confidence interval: 0.35-0.91). The prototype had low sensitivity (40%, 19-61%) and moderate specificity (78%, 65-92%). Using the same questionnaire with a modified decision algorithm, new prototypes were generated with range of high sensitivity (80-100%) and specificity (89-97%) values.ConclusionsThe RCPST aims to identify patients that should be referred for consideration for neurostimulation. The final implant decision requires appropriate neurological diagnostic workup, psychological assessment, and trial stimulation. RCPST was considered practical for routine clinical practice and contained appropriate questions. Sensitivity needs to be improved. A future study should select and validate the ideal RCPST prototype.

Background Spinal cord stimulation (SCS), by virtue of its historically described up-front costs and level of invasiveness, has been relegated by several complex regional pain syndrome (CRPS) treatment algorithms to a therapy of last resort. Newer information regarding safety, cost, and efficacy leads us to believe that SCS for the treatment of CRPS should be implemented earlier in a treatment algorithm using a more comprehensive approach. Methods We reviewed the literature on pain care algorithmic thinking and applied the safety, appropriateness, fiscal or cost neutrality, and efficacy (S.A.F.E.) principles to establish an appropriate position for SCS in an algorithm of pain care. Results and Conclusion Based on literature-contingent considerations of safety, efficacy, cost efficacy, and cost neutrality, we conclude that SCS should not be considered a therapy of last resort for CRPS but rather should be applied earlier (e.g., three months) as soon as more conservative therapies have failed.