Persistent Spinal Pain Syndrome: A Proposal for Failed Back Surgery Syndrome and ICD-11.

OBJECTIVE: For many medical professionals dealing with patients with persistent pain following spine surgery, the term Failed back surgery syndrome (FBSS) as a diagnostic label is inadequate, misleading, and potentially troublesome. It misrepresents causation. Alternative terms have been suggested, but none has replaced FBSS. The International Association for the Study of Pain (IASP) published a revised classification of chronic pain, as part of the new International Classification of Diseases (ICD-11), which has been accepted by the World Health Organization (WHO). This includes the term Chronic pain after spinal surgery (CPSS), which is suggested as a replacement for FBSS. METHODS: This article provides arguments and rationale for a replacement definition. In order to propose a broadly applicable yet more precise and clinically informative term, an international group of experts was established. RESULTS: 14 candidate replacement terms were considered and ranked. The application of agreed criteria reduced this to a shortlist of four. A preferred option-Persistent spinal pain syndrome-was selected by a structured workshop and Delphi process. We provide rationale for using Persistent spinal pain syndrome and a schema for its incorporation into ICD-11. We propose the adoption of this term would strengthen the new ICD-11 classification. CONCLUSIONS: This project is important to those in the fields of pain management, spine surgery, and neuromodulation, as well as patients labeled with FBSS. Through a shift in perspective, it could facilitate the application of the new ICD-11 classification and allow clearer discussion among medical professionals, industry, funding organizations, academia, and the legal profession.

The Pathways and Processes Underlying Spinal Transmission of Low Back Pain: Observations From Dorsal Root Ganglion Stimulation Treatment.

BACKGROUND: Dorsal root ganglion stimulation (DRG-S) is a novel approach to treat chronic pain. Lead placement at L2 has been reported to be an effective treatment for axial low back pain (LBP) primarily of discogenic etiology. We have recently shown, in a diverse cohort including cases of multilevel instrumentation following extensive prior back surgeries, that DRG-S lead placement at T12 is another promising target. Local effects at the T12 DRG, alone, are insufficient to explain these results. MATERIALS AND METHODS: We performed a literature review to explore the mechanisms of LBP relief with T12 DRG-S. FINDINGS: Branches of individual spinal nerve roots innervate facet joints and posterior spinal structures, while the discs and anterior vertebrae are carried via L2, and converge in the dorsal horn (DH) of the spinal cord at T8-T9. The T12 nerve root contains cutaneous afferents from the low back and enters the DH of the spinal cord at T10. Low back Aδ and C-fibers then ascend via Lissauer's tract (LT) to T8-T9, converging with other low back afferents. DRG-S at T12, then, results in inhibition of the converged low back fibers via endorphin-mediated and GABAergic frequency-dependent mechanisms. Therefore, T12 lead placement may be the optimal location for DRG-S to treat LBP.

Direct Peripheral Nerve Stimulation for the Treatment of Complex Regional Pain Syndrome: A 30-Year Review.

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.

Mechanisms for the Clinical Utility of Low-Frequency Stimulation in Neuromodulation of the Dorsal Root Ganglion.

BACKGROUND: Dorsal root ganglion stimulation (DRG-S) involves the electrical modulation of the somata of afferent neural fibers to treat chronic pain. DRG-S has demonstrated clinical efficacy at frequencies lower than typically used with spinal cord stimulation (SCS). In a clinical study, we found that the frequency of DRG-S can be tapered to a frequency as low as 4 Hz with no loss of efficacy. This review discusses possible mechanisms of action underlying effective pain relief with very low-frequency DRG-S. MATERIALS AND METHODS: We performed a literature review to explore the role of frequency in neural transmission and the corresponding relevance of frequency settings with neuromodulation. FINDINGS: Sensory neural transmission is a frequency-modulated system, with signal frequency determining which mechanisms are activated in the dorsal horn. In the dorsal horn, low-frequency signaling (<20 Hz) activates inhibitory processes while higher frequencies (>25 Hz) are excitatory. Physiologically, low-threshold mechanoreceptors (LTMRs) fibers transmit or modulate innocuous mechanical touch at frequencies as low as 0.5-5 Hz, while nociceptive fibers transmit pain at high frequencies. We postulate that very low-frequency DRG-S, at least partially, harnesses LTMRs and the native endogenous opioid system. Utilizing lower stimulation frequency decreases the total energy delivery used for DRG-S, extends battery life, and facilitates the development of devices with smaller generators.

Very Low Frequencies Maintain Pain Relief From Dorsal Root Ganglion Stimulation: An Evaluation of Dorsal Root Ganglion Neurostimulation Frequency Tapering.

BACKGROUND: Dorsal root ganglion neurostimulation (DRG-S) is effective in treating various refractory chronic pain syndromes. In preclinical studies, DRG-S at very low frequencies (<5 Hz) reduces excitatory output in the superficial dorsal horn. Clinically, we have also observed the effectiveness of DRG-S at low frequencies. We conducted a case series to describe the effect of very low-frequency DRG-S stimulation on clinical outcomes. MATERIALS AND METHODS: DRG-S for refractory low back pain was initiated at parameters consistent with published values. Thereafter, the stimulation frequency of DRG-S was reduced in a stepwise fashion to the lowest frequency that maintained pain relief. Pain intensity, disability, and general health status data were collected at baseline, prior to initiation of tapering, and at four weeks after each patient's lowest effective stimulation frequency was reached. RESULTS: After device activation (N = 20), DRG-S frequency was tapered from 16 to 4 Hz over a 4- to 17-week period, reducing charge-per-second by nearly two-thirds. Even so, pain relief was maintained at more than 75%, with consistent findings in the other measures. CONCLUSION: DRG-S may have utility in treating chronic pain at lower stimulation frequencies than previously recognized. We have previously theorized that the mechanism of action may involve preferential recruitment of low-threshold mechanoreceptor fibers via the endogenous opioid system. Of clinical relevance, lower frequency stimulation maintains DRG-S efficacy regarding improvements in pain, disability, and quality of life. It can extend battery life and may potentially lead to the development of smaller implantable pulse generators.

Refractory Chronic Pain Screening Tool (RCPST): a feasibility study to assess practicality and validity of identifying potential neurostimulation candidates.

OBJECTIVE: An 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. DESIGN: Consecutive 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." RESULTS: The 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. CONCLUSIONS: The 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.

The appropriate use of neurostimulation: new and evolving neurostimulation therapies and applicable treatment for chronic pain and selected disease states. Neuromodulation Appropriateness Consensus Committee.

INTRODUCTION: The International Neuromodulation Society (INS) has determined that there is a need to provide an expert consensus that defines the appropriate use of neuromodulation technologies for appropriate patients. The Neuromodulation Appropriateness Consensus Committee (NACC) was formed to give guidance to current practice and insight into future developments. METHODS: The INS executive board selected members of the international scientific community to analyze scientific evidence for current and future innovations and to use clinical experience to fill in any gaps in information. The NACC used PubMed and Google Scholar to obtain current evidence in the field and used clinical and research experience to give a more complete picture of the innovations in the field. RESULTS: The NACC has determined that currently approved neurostimulation techniques and technologies have expanded our ability to treat patients in a more effective and specific fashion. Despite these advances, the NACC has identified several additional promising technologies and potential applications for neurostimulation that could move this field forward and expand the applicability of neuromodulation. CONCLUSIONS: The NACC concludes that the field of neurostimulation is an evolving and rapidly changing one that will lead to improved patient access, safety, and outcomes.

The appropriate use of neurostimulation of the spinal cord and peripheral nervous system for the treatment of chronic pain and ischemic diseases: the Neuromodulation Appropriateness Consensus Committee.

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.

Administering ziconotide and monitoring patients treated with ziconotide: expert opinions.

Some patients with chronic pain who are intolerant of or refractory to treatment with systemic analgesics may benefit from intrathecal therapy. Ziconotide is the first nonopioid analgesic approved by the United States Food and Drug Administration for intrathecal administration. Several randomized, double-blind, placebo-controlled clinical trials have demonstrated the efficacy and safety of ziconotide. However, the maximum recommended dosing and titration schedule provided in the prescribing information may be too aggressive for some patients, and experience has demonstrated that ziconotide is better tolerated with slower titration to a lower maximum dose. Efficacy can be assessed by an evaluation of changes in pain, functionality, and quality of life. Cognitive adverse events may be subtle; therefore, it is important that health care professionals not only monitor patients for signs and symptoms of cognitive adverse events, but also teach family members how to do the same. Careful patient assessment and monitoring can help optimize the potential benefit from treatment with ziconotide.

Polyanalgesic Consensus Conference 2012: recommendations for the management of pain by intrathecal (intraspinal) drug delivery: report of an interdisciplinary expert panel.

INTRODUCTION: The use of intrathecal (IT) infusion of analgesic medications to treat patients with chronic refractory pain has increased since its inception in the 1980s, and the need for clinical research in IT therapy is ongoing. The Polyanalgesic Consensus Conference (PACC) panel of experts convened in 2000, 2003, and 2007 to make recommendations on the rational use of IT analgesics based on preclinical and clinical literature and clinical experiences. METHODS: The PACC panel convened again in 2011 to update the standard of care for IT therapies to reflect current knowledge gleaned from literature and clinical experience. A thorough literature search was performed, and information from this search was provided to panel members. Analysis of published literature was coupled with the clinical experience of panel members to form recommendations regarding the use of IT analgesics to treat chronic pain. RESULTS: After a review of literature published from 2007 to 2011 and discussions of clinical experience, the panel created updated algorithms for the rational use of IT medications for the treatment of neuropathic pain and nociceptive pain. CONCLUSIONS: The advent of new algorithmic tracks for neuropathic and nociceptive pain is an important step in improving patient care. The panel encourages continued research and development, including the development of new drugs, devices, and safety recommendations to improve the care of patients with chronic pain.

Polyanalgesic Consensus Conference--2012: consensus on diagnosis, detection, and treatment of catheter-tip granulomas (inflammatory masses).

INTRODUCTION: Continuous intrathecal infusion of drugs to treat chronic pain and spasticity has become a standard part of the algorithm of care. The use of opioids has been associated with noninfectious inflammatory masses at the tip of the intrathecal catheter, which can result in neurologic complications. METHODS: The Polyanalgesic Consensus Conference is a meeting of a group of well-published and experienced practitioners; the purpose of the meeting is to update the standard of care for intrathecal therapies to reflect current knowledge gleaned from literature and clinical experience. An exhaustive literature search was performed, and information from this search was provided to panel members. Analysis of the published literature was coupled with the clinical experience of panel participants to form recommendations regarding intrathecal inflammatory masses or granulomas. RESULTS: The panel has made recommendations for the prevention, diagnosis, and management of intrathecal granulomas. CONCLUSION: The use of chronic infusions of intrathecal opioids is associated with the formation of inflammatory masses at the intrathecal catheter tip in a small minority of treated patients. Nonetheless, the appearance of these space-occupying lesions can lead to devastating neurologic sequelae. The prevention, early detection, and successful treatment of intraspinal granulomas are important considerations when offering intrathecal drug therapy to patients with chronic intractable pain.

Polyanalgesic Consensus Conference--2012: recommendations on trialing for intrathecal (intraspinal) drug delivery: report of an interdisciplinary expert panel.

INTRODUCTION: Trialing for intrathecal pump placement is an essential part of the decision-making process in placing a permanent device. In both the United States and the international community, the proper method for trialing is ill defined. METHODS: The Polyanalgesic Consensus Conference (PACC) is a group of well-published experienced practitioners who meet to update the state of care for intrathecal therapies on the basis of current knowledge in the literature and clinical experience. Anexhaustive search is performed to create a base of information that the panel considers when making recommendations for best clinical practices. This literature, coupled with clinical experience, is the basis for recommendations and for identification of gaps in the base of knowledge regarding trialing for intrathecal pump placement. RESULTS: The panel has made recommendations for the proper methods of trialing for long-term intrathecal drug delivery. CONCLUSION: The use of intrathecal drug delivery is an important part of the treatment algorithm for moderate to severe chronic pain. It has become common practice to perform a temporary neuroaxial infusion before permanent device implantation. On the basis of current knowledge, the PACC has developed recommendations to improve care. The need to update these recommendations will be very important as new literature is published.

Polyanalgesic Consensus Conference--2012: recommendations to reduce morbidity and mortality in intrathecal drug delivery in the treatment of chronic pain.

INTRODUCTION: Targeted intrathecal drug infusion to treat moderate to severe chronic pain has become a standard part of treatment algorithms when more conservative options fail. This therapy is well established in the literature, has shown efficacy, and is an important tool for the treatment of both cancer and noncancer pain; however, it has become clear in recent years that intrathecal drug delivery is associated with risks for serious morbidity and mortality. METHODS: The Polyanalgesic Consensus Conference is a meeting of experienced implanting physicians who strive to improve care in those receiving implantable devices. Employing data generated through an extensive literature search combined with clinical experience, this work group formulated recommendations regarding awareness, education, and mitigation of the morbidity and mortality associated with intrathecal therapy to establish best practices for targeted intrathecal drug delivery systems. RESULTS: Best practices for improved patient care and outcomes with targeted intrathecal infusion are recommended to minimize the risk of morbidity and mortality. Areas of focus include respiratory depression, infection, granuloma, device-related complications, endocrinopathies, and human error. Specific guidance is given with each of these issues and the general use of the therapy. CONCLUSIONS: Targeted intrathecal drug delivery systems are associated with risks for morbidity and mortality that can be devastating. The panel has given guidance to treating physicians and healthcare providers to reduce the incidence of these problems and to improve outcomes when problems occur.

Accidental subdural spinal cord stimulator lead placement and stimulation.

OBJECTIVES: Neuromodulation with spinal cord stimulation has become an increasingly employed intervention for treatment of a variety of neuropathic pain states. As prevalence increases, so does the incidence of complications. Currently, there is sparse literature describing spinal cord stimulation lead placement and stimulation characteristics in the subdural space. In this case report we describe subdural lead placement and the associated stimulation parameters, and provide evidence-based support to initiate a dialog to further reduce procedural morbidity and mortality. MATERIALS AND METHODS: This study is a case report following lead placement during permanent percutaneous spinal cord stimulator placement and stimulation testing. The lead placement and stimulation characteristics were suggestive of extra-epidural lead placement. RESULTS: Using the same cathode/anode configuration (1:anode, 3:cathode, 5:anode), frequency of 40 Hz and pulse width of 650 microseconds, sequential stimulation was performed. Summarizing, the testing demonstrated similar impedance for the left and right leads (within 30 ohms) of approximately 300 ohms, and a large discrepancy in current of 3.2 mA for the left and 0.9 mA for the right. The patient reported "painful intense" stimulation with right lead stimulation. CONCLUSIONS: Evidence suggesting subdural lead placement include the lack of cerebrospinal-fluid despite lavage, the absence of post-dural puncture headache, the recent evidence of intentional and reproducible subdural anesthesia, and the conductive properties of the dural spinal elements. It can be argued that subdural lead placement may occur unrecognized more frequently than originally anticipated.

Long-term outcomes of spinal cord stimulation with paddle leads in the treatment of complex regional pain syndrome and failed back surgery syndrome.

INTRODUCTION: Spinal cord stimulation (SCS) is frequently used to treat chronic, intractable back, and leg pain. Implantation can be accomplished with percutaneous leads or paddle leads. Although there is an extensive literature on SCS, the long-term efficacy, particularly with paddle leads, remains poorly defined. Outcome measure choice is important when defining therapeutic efficacy for chronic pain. Numerical rating scales such as the NRS-11 remain the most common outcome measure in the literature, although they may not accurately correlate with quality of life improvements and overall satisfaction. METHODS: We reviewed the medical records of patients with failed back surgery syndrome (FBSS) or complex regional pain syndrome (CRPS) implanted with SCS systems using paddle leads between 1997 and 2008 at the Cleveland Clinic with a minimum six-month follow-up. Patients were contacted to fill out a questionnaire evaluating outcomes with the NRS-11 as well as overall satisfaction. RESULTS: A total of 35 eligible patients chose to participate. More than 50% of the patients with CRPS reported greater than 50% pain relief at a mean follow-up of 4.4 years. Approximately 30% of the FBSS patients reported a 50% or greater improvement at a mean follow-up of 3.8 years. However, 77.8% of patients with CRPS and 70.6% of patients with FBSS indicated that they would undergo SCS surgery again for the same outcome. CONCLUSION: Patients with CRPS and FBSS have a high degree of satisfaction, indexed as willingness to undergo the same procedure again for the same outcome at a mean follow-up of approximately four years. The percentage of satisfaction with the SCS system is disproportionally greater than the percentage of patients reporting 50% pain relief, particularly among patients with FBSS. This suggests that the visual analog scale may not be the optimal measure to evaluate long-term outcomes in this patient population.

Evidence-based interventional pain medicine according to clinical diagnoses. 16. Complex regional pain syndrome.

Complex regional pain syndrome (CRPS), formerly known as reflex sympathetic dystrophy is a pain syndrome with an unclear pathophysiology and unpredictable clinical course. The disease is often therapy resistant, the natural course not always favorable. The diagnosis of CRPS is based on signs and symptoms derived from medical history and physical examination. Pharmacological pain management and physical rehabilitation of limb function are the main pillars of therapy and should be started as early as possible. If, however, there is no improvement of limb function and persistent severe pain, interventional pain management techniques may be considered. Intravenous regional blocks with guanethidine did not prove superior to placebo but frequent side effects occurred.Therefore this technique receives a negative recommendation (2 A-). Sympathetic block is the interventional treatment of first choice and has a 2 B+ rating. Ganglion stellatum (stellate ganglion) block with repeated local anesthetic injections or by radiofrequency denervation after positive diagnostic block is documented in prospective and retrospective trials in patients suffering from upper limb CRPS. Lumbar sympathetic blocks can be performed with repeated local anesthetic injections. For a more prolonged lumbar sympathetic block radiofrequency treatment is preferred over phenol neurolysis because effects are comparable whereas the risk for side effects is lower (2 B+). For patients suffering from CRPS refractory to conventional treatment and sympathetic blocks, plexus brachialis block or continuous epidural infusion analgesia coupled with exercise therapy may be tried (2 C+). Spinal cord stimulation is recommended if other treatments fail to improve pain and dysfunction (2 B+). Alternatively peripheral nerve stimulation can be considered, preferentially in study conditions (2 C+).

Electrical stimulation of sphenopalatine ganglion for acute treatment of cluster headaches.

INTRODUCTION: Cluster headaches (CH) are primary headaches marked by repeated short-lasting attacks of severe, unilateral head pain and associated autonomic symptoms. Despite aggressive management with medications, oxygen therapy, nerve blocks, as well as various lesioning and neurostimulation therapies, a number of patients are incapacitated and suffering. The sphenopalatine ganglion (SPG) has been implicated in the pathophysiology of CH and has been a target for blocks, lesioning, and other surgical approaches. For this reason, it was selected as a target for an acute neurostimulation study. METHODS: Six patients with refractory chronic CH were treated with short-term (up to 1 hour) electrical stimulation of the SPG during an acute CH. Headaches were spontaneously present at the time of stimulation or were triggered with agents known to trigger clusters headache in each patient. A standard percutaneous infrazygomatic approach was used to place a needle at the ipsilateral SPG in the pterygopalatine fossa under fluoroscopic guidance. Electrical stimulation was performed using a temporary stimulating electrode. Stimulation was performed at various settings during maximal headache intensity. RESULTS: Five patients had CH during the initial evaluation. Three returned 3 months later for a second evaluation. There were 18 acute and distinct CH attacks with clinically maximal visual analog scale (VAS) intensity of 8 (out of 10) and above. SPG stimulation resulted in complete resolution of the headache in 11 attacks, partial resolution (>50% VAS reduction) in 3, and minimal to no relief in 4 attacks. Associated autonomic features of CH were resolved in each responder. Pain relief was noted within several minutes of stimulation. CONCLUSION: Sphenopalatine ganglion stimulation can be effective in relieving acute severe CH pain and associated autonomic features. Chronic long-term outcome studies are needed to determine the utility of SPG stimulation for management and prevention of CH.

Plasticity of complex regional pain syndrome (CRPS) in children.

Complex regional pain syndrome I (CRPS I) is defined by the International Association for the Study of Pain (IASP) criteria to include pain that is disproportionate to the inciting event, sensory disturbances such as allodynia/ hyperalgesia, autonomic dysfunction, and motor dysfunction that usually occurs after trauma that is frequently trivial and generally expressed in an extremity. These symptoms are well described in the adult population, but there are relatively few data or reports of its prevalence in the pediatric population. Recent studies have demonstrated that unlike the adult population, about 90% of the cases reported are females in a range of 8 to 16 years, the youngest being 3 years old. There tends to be delay in recognizing the diagnosis, which may be as long as 4 months. In contrast to adults, the response to treatment, particularly exercise therapy with behavioral management will achieve almost 97% remission. While the pathophysiology is poorly understood, many features, particularly the neurologic abnormalities, suggest both peripheral and central nervous system involvement. Peripheral small fiber neuropathy as an etiology and inflammation involving small nerve fibers (neurogenic inflammatory pain) has been suggested. A tissue inflammatory etiology has been investigated over the past 25 years. However, these inflammatory aspects differ from those seen in other conditions involving tissue inflammation. The suggestion that CRPS in children is a different clinical entity than that seen in the adult, is probably incorrect, as recent evidence would suggest that the pathophysiology is most likely identical involving endocrine, behavioral, developmental, and environmental factors that distinguish clinical presentation in children from the adult. Behavioral management is a mandatory accompaniment of any program of exercise therapy and the sometimes extreme sensory disturbances and parental enmeshment do distinguish the clinical presentation from that in the adult. Interventional procedures may be required in the face of extreme allodynia preventing exercise therapy, and in occasional cases interruption of the sympathetic nerves may reverse this symptom in a few children. Occasionally, continuous analgesia techniques such as that which can be delivered by tunneled epidural catheter or an externalized neurostimulator (spinal cord stimulation) for short periods of time are effective.