Behavioral evidence showing the predominance of diffuse pain stimuli over discrete stimuli in influencing perception

This experiment was directed toward determining the relative effectiveness of discrete and diffuse pain stimuli in influencing perception and behavior. Shocks to the footpads were use to activate the discrete pain pathways. In the first phase of this experiment, cats were trained to escape from foot shock in a shuttle box. Current applied to the feet was varied in ascending and descending sequences for each animal according to the psychophysical method of limits and each animal was trained until stable thresholds for escape responding were achieved. In the second phase of the experiment, the effect on behavior of simultaneous activation of both the discrete and diffuse pain systems was assessed. The principal finding in this experiment was that escape responding that was well established when foot shock was presented alone was routinely abolished on trials when tooth shock and foot shock were presented together. These results were interpreted as indicating that the diffuse pain system was prepotent in influencing behavior when both the discrete and diffuse pain systems were activated simultaneously.     

慢性疼痛与器质性疼痛心理学特征的对照研究

目的 旨在探讨慢性疼痛与器质性疼痛心理学特征的差异。方法 采用ＳＣＬ－９０、ＬＥＳ、ＳＳＲＳ、ＤＳＱ、ＨＡＭＤ、ＨＡＭＡ等尽理学量表对５９例慢性疼痛（ＣＰ）与５０例器质性疼痛（ＯＰ）患者进行对照研究,并用ｔ检验对数据进行统计分析。结果 与ＯＰ组相比较,ＣＰ组有较多的生活支持相对缺乏,较易动用不成熟防御方式,有明显的抑郁、焦虑情绪。结论 慢性疼痛与心理社会因素密切相关。     

Patient perception of pain versus observed pain behavior during a standardized electrodiagnostic test

Introduction: Clinicians often assume that observations of pain behavior are adequate for assessment of patient pain perception during procedures. This has not been tested during a standardized electrodiagnostic experience. Methods: During a prospective trial including extensive, standardized electrodiagnostic testing on persons with lumbar stenosis, vascular claudication, and asymptomatic volunteers, the subjects and an observer rated levels of pain. Results: In 60 subjects, observers significantly under‐rated pain (Visual Analog Scale 3.17 ± 2.23 vs. 4.38 ± 2.01, t = −4.577, df = 59, P < 0.001). Perceived pain during testing related to bodily pain as measured by the visual analog, McGill, Pain Disability, and Quebec scales, but not age, duration of symptoms, Tampa kinesiphobia, Center for Epidemiological Studies Depression scale, or SF‐36 health quality of life. Conclusions: Persons with worse pain syndromes may perceive more pain during testing than others. Clinicians and researchers should understand that patients may have more pain than they recognize. Muscle Nerve 51 : 185–191, 2015     

Long‐Term Intrathecal Ziconotide Therapy: A Case Study and Discussion

This case study describes the therapeutic result of intrathecal administration of ziconotide, a new synthetic neurotoxin derived from the venom of the Philippine marine snail, Conus Magus, to a 48‐year‐old male with chronic, and previously untreatable, neuropathic pain of an undeterminable etiology. The patient suffered tactile allodynia and reported his baseline pain intensity to be 80 mm on the 100 mm Visual Analog Scale for Pain Intensity. After responding affirmatively to treatment in a blinded placebo‐controlled trial, the patient enrolled in a long‐term, open‐label trial. Currently, the patient rates his pain at 16 mm and enjoys an improved quality of life. This result suggests that treatment with ziconotide may provide outstanding relief to patients with chronic pain while sparing them the unpleasant side effects associated with other treatments.     

Development and Validation of the Dystonia-Pain Classification System: A Multicenter Study

Background

Dystonia is associated with disabling nonmotor symptoms like chronic pain (CP), which is prevalent in dystonia and significantly impacts the quality of life (QoL). There is no validated tool for assessing CP in dystonia, which substantially hampers pain management.

Objective

The aim was to develop a CP classification and scoring system for dystonia.

Methods

A multidisciplinary group was established to develop the Dystonia-Pain Classification System (Dystonia-PCS). The classification of CP as related or unrelated to dystonia was followed by the assessment of pain severity score, encompassing pain intensity, frequency, and impact on daily living. Then, consecutive patients with inherited/idiopathic dystonia of different spatial distribution were recruited in a cross-sectional multicenter validation study. Dystonia-PCS was compared to validated pain, mood, QoL, and dystonia scales (Brief Pain Inventory, Douleur Neuropathique-4 questionnaire, European QoL-5 Dimensions-3 Level Version, and Burke–Fahn–Marsden Dystonia Rating Scale).

Results

CP was present in 81 of 123 recruited patients, being directly related to dystonia in 82.7%, aggravated by dystonia in 8.8%, and nonrelated to dystonia in 7.5%. Dystonia-PCS had excellent intra-rater (Intraclass Correlation Coefficient - ICC: 0.941) and inter-rater (ICC: 0.867) reliability. In addition, pain severity score correlated with European QoL-5 Dimensions-3 Level Version's pain subscore (r = 0.635, P < 0.001) and the Brief Pain Inventory's severity and interference scores (r = 0.553, P < 0.001 and r = 0.609, P < 0.001, respectively).

Conclusions

Dystonia-PCS is a reliable tool to categorize and quantify CP impact in dystonia and will help improve clinical trial design and management of CP in patients affected by this disorder. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.     

Atypical electrophysiological activity during pain observation in amputees who experience synaesthetic pain

There are increasing reports of people experiencing pain when observing pain in another. This describes the phenomenon of synaesthetic pain which, until recently, had been primarily reported in amputees with phantom pain. In the current study, we used electroencephalography (EEG) to investigate how amputees who experience synaesthetic pain process pain observed in another. Participants were grouped according to amputees who experience phantom and synaesthetic pain (n=8), amputees who experience phantom pain but not synaesthetic pain (n=10) and healthy controls (n=10). Participants underwent EEG as they observed still images of hands and feet in potentially painful and non-painful situations. We found that pain synaesthetes showed some reduced event-related potential (ERP) components at certain electrode sites, and reduced theta- and alpha band power amplitude at a central electrode. The finding of reduced ERP amplitude and theta band power may reflect inhibition of the processing of observed pain (e.g. avoidance/guarding as a protective strategy), and reduced alpha band power may indicate a disinhibition in control processes that may result in synaesthetic pain. These results provide the first documentation of atypical neurophysiological activity in amputees who experience synaesthetic pain when processing pain in another.     

Antidepressants for cancer pain and other painful syndromes with deafferentation component: comparison of Amitriptyline and Trazodone

The Authors report a clinical multicentre experience with antidepressant agents (trazodone and amitriptyline) in the treatment of chronic cancer pain with deafferentation component. Fortyfive patients were admitted to the study: 27 with oncological peripheral nerve lesions, 6 with post herpetic neuralgias, 10 with not oncological nerve lesions, 2 with central nervous lesions. Almost all of them were already being treated with NSAID associated with weak or strong opioids. A random double blind study was performed: 23 patients were treated with trazodone, 22 with amitryptiline. In the assessment of results, pain intensity, hours of sleep, hours standing and lying, side effects, mood, anxiety, weakness were all taken into consideration. The therapeutic analgesic efficacy of the two drugs proved to be similar.

---

Sommario Gli Autori riportano uno studio clinico multicentrico sull'uso di farmaci antidepressivi (amitriptilina e trazodone) nel trattamento del dolore cronico da cancro con componente da deafferentazione. Quarantacinque pazienti hanno partecipato allo studio, 27 con lesioni nervose periferiche oncologiche, 6 con nevralgia postherpetica, 10 con lesioni nervose non oncologiche e 2 con lesioni nervose centrali. Quasi tutti i pazienti erano già in trattamento con farmaci anti-infiammatori non steroidei associati a narcotici deboli o forti. è stato effettuato uno studio randomizzato in doppio cieco: 22 pazienti sono stati trattati con amitriptilina e 23 con trazodone. Nella valutazione dei risultati si è tenuto conto di: intensità del dolore, ore di sonno, ore passate in piedi o a letto, effetti collaterali, umore, ansietà, debolezza. L'efficacia terapeutica analgesica dei due farmaci si è dimostrata sovrapponibile.

     

Treatment of Multifocal Pain with Spinal Cord Stimulation

Introduction: We report a retrospective case study of combined treatment of cancer‐related pain and chronic low back and lower extremity pain related to postlaminectomy syndrome (PLS) with one spinal cord stimulation (SCS) system. Methods: The patient underwent an uneventful SCS trial with percutaneous placement of two temporary eight‐electrode leads (Medtronic Inc., Minneapolis, MN) placed at the level of T8‐T9‐T10 and T5‐T6‐T7. Results: After successful trial, he was implanted with permanent leads and generator, reporting sustained pain relief at 12‐month follow‐up visit. Discussion: SCS is a trialable, reversible, and interactive therapy permitting patients to control the level of stimulation they feel based on their degree of pain. Conclusion: SCS provides an effective, alternative treatment for select patients with cancer‐related chest wall pain and pain related to PLS who have failed conservative treatment.     

运动皮质电刺激术治疗顽固性神经病理性疼痛

目的研究运动皮质电刺激术（motor cortex stimulation,MCS）治疗顽固性神经病理性疼痛的临床应用。方法脑卒中后疼痛9例,脊髓损伤后疼痛3例,幻肢痛2例。均行MCS治疗,同期植入刺激电极和脉冲发生器。采用视觉模拟疼痛评分（VAS）评价疗效。结果术后疼痛均不同程度减轻,1个月以内镇痛疗效较满意,VAS评分较术前显著降低（P〈0．01）。随访1。5年．多数病人镇痛效果出现波动,调整刺激参数后仍能获得镇痛疗效,疼痛较术前减轻10％～90％,脑卒中后疼痛的长期疗效要好于脊髓损伤后疼痛和幻肢痛。结论MCS是治疗神经病理性疼痛的一种新方法,具有疗效肯定、可调节等优点,术后刺激参数的调整对疗效的影响至关重要。     

上海地区帕金森病患者慢性疼痛及其有关影响因素的临床研究

目的评估上海地区原发性帕金森病(PD)患者中与PD相关疼痛症状的患病率及流行病学特征。方法对上海市12个综合性医院共1 058例诊断明确的原发性PD患者进行结构问卷调查。包括运动障碍的严重程度、抗PD治疗、疼痛相关数据(疼痛发作时间点、持续时间、程度、部位、其他症状、治疗情况)等资料进行收集与分析。结果 1 058例PD患者中1 096例完成调查,约有28.8%(296例)有PD相关性疼痛症状。在PD早期阶段,与男性PD疼痛患者比较女性具有发病率高(P0.05)、年龄层级高(P0.05)、发病年龄高(P0.05)、疼痛频率高(P0.05)、疼痛先于运动障碍症状出现的频率高(P0.05)和疼痛持续时间较长(P0.05)的特点。PD合并疼痛患者就无合并疼痛患者而言,具有较大的左旋多巴等效剂量(P0.05)、睡眠障碍(P0.05)和(或)运动障碍的高发生率(P0.05)。最常见的疼痛类型是骨骼肌疼痛,其次是肌张力障碍疼痛;男性患者疼痛持续时间较女性患者短;疼痛多在服用抗PD药物后出现。结论慢性PD相关性疼痛是常见且复杂的并发症,发病机制复杂;PD慢性疼痛的综合治疗是富有挑战的课题,最终会找到有效的治疗策略。     

Application of Spinal Cord Stimulation for the Treatment of Abdominal Visceral Pain Syndromes: Case Reports

Spinal cord stimulation (SCS) has traditionally been applied to the treatment of neuropathic pain with good to excellent outcomes. Visceral pain syndromes can be just as debilitating and disabling as somatic and neuropathic pain, however, there seems to be a general lack of consensus on appropriate treatment strategies for these disorders. We present here several case studies to demonstrate the viscerotomal distribution of abdominal visceral pain pathways and the application of traditional SCS techniques for its management. Nine patients, experiencing abdominal visceral pain due to various conditions including chronic nonalcoholic pancreatitis, post‐traumatic splenectomy, and generalized abdominal pain secondary to laparotomies, were treated with SCS. Efficacy of treatment was evaluated using the Visual Analog Scale (VAS) for pain intensity and a reduction, if any, in opioid intake. There was an overall mean reduction of 4.9 points in the VAS score for pain intensity and a substantial (> 50%) decrease in narcotic use. All patients were followed for more than one year with excellent outcomes and minimal complications. We conclude, based on these case reports, that SCS might be an effective, nondestructive, and reversible treatment modality for abdominal visceral pain disorders.     

Electrical devices for functional visceral pain

Several studies have documented correction of dysmotility in several regions of the gastrointestinal tract based on electrical stimulation of extrinsic nerves supplying those regions. In this issue of Neurogastroenterology and Motility, Ma et al. (2023) document the effect of transcutaneous neuromodulation applied by acustimulation at ST36 for ineffective esophageal motility in patients with gastroesophageal reflux disease. In addition to motor effects, there were also significant effects on GERD symptoms, raising the question whether extrinsic electrical nerve stimulation of the gut can reduce symptoms through effects that target sensation. This brief review summarizes evidence regarding the application of electrical acustimulation, transauricular electrical stimulation, and sacral electrical or magnetic stimulation to reduce abdominal or pelvic pain.     

Accuracy and efficacy of intrathecal administration of morphine sulfate for treatment of intractable pain using the Prometra® Programmable Pump

Objectives: Intrathecal infusion pumps are increasingly used to deliver analgesics for chronic intractable pain. This trial evaluated the accuracy and efficacy of the new Prometra® Programmable Pump System for intrathecal administration of morphine sulfate to treat chronic intractable pain. Methods: One hundred and ten patients were given continuous intrathecal morphine sulfate and assessed monthly for up to six months. Accuracy was determined as the ratio of delivered to programmed drug volume (DP ratio). Efficacy was assessed using the visual analog and numeric rating scales and the Oswestry Disability Index. Results: The mean accuracy of the Prometra pump was 97.1%, with a 90% confidence interval of 96.2–98.0%. Decreases in pain and disability were reported at 68.4% of patient visits. No unanticipated adverse events or device complications were reported. Conclusions: The Prometra pump provides an accurate, effective, and safe system for intrathecal administration of morphine sulfate for treatment of chronic intractable pain.