A Double-Blind, Placebo-Controlled Study of Ultrasound-Guided Pulsed Radiofrequency Treatment of the Saphenous Nerve for Refractory Osteoarthritis-Associated Knee Pain.

BACKGROUND: While the efficacy of pulsed radiofrequency (PRF) for shoulder pain has been demonstrated, its efficacy on the saphenous nerves for knee osteoarthritis (OA)-associated pain has only been reported in observational studies. OBJECTIVES: The aim of this study was to compare saphenous nerve PRF to placebo for knee OA-associated pain. STUDY DESIGN: Patients, practitioners, and outcome assessor-blinded randomized placebo-controlled trial. SETTING: Pain management clinics at 2 hospitals in Japan. METHODS: Patients were randomly allocated to the PRF (n = 37) or placebo group (n = 33). Patients aged 40-85 years with refractory anteromedial knee pain. PRF in the saphenous nerve under ultrasound guidance. The placebo group underwent the same procedure, but with motor stimulation. The primary endpoint was the average pain intensity measured using the visual analog scale (VAS) at the 12-week post-treatment visit; secondary outcomes included the average VAS at 1 and 4 weeks, and pain intensities at rest, in flexion, at standing, and at walking. Other secondary outcomes were knee pain, symptoms, activities of daily living, knee-related quality of life, mobility, range of motion, and adverse events. RESULTS: In the PRF group, the mean VAS score was 52.41 ± 26.17 at 12 weeks, while in the sham group, the mean VAS score was 63.06 ± 27.12 (P < 0.05). There were no significant differences between the groups in any of the secondary outcomes. LIMITATIONS: Patients with comorbidities were excluded from this study. The follow-up time was limited to 12 weeks. CONCLUSIONS: Ultrasound-guided saphenous nerve PRF proved to be effective for at least 12 weeks in patients with knee OA and showed no adverse events.

Validation of the Japanese version of the Bath CRPS Body Perception Disturbance Scale for CRPS.

PURPOSE: Body perception disturbance is a common symptom and may be one of the key targets of treatment intervention in complex regional pain syndrome (CRPS). As a comprehensive assessment tool of body perception in patients with CRPS, the Bath Body Perception Disturbance Scale (BPDS) was developed, and its adequate reliability and validity have been reported. However, there is no available Japanese version. Therefore, this study aimed to develop a Japanese version of BPDS (BPDS-J) and to investigate the validity of this scale in Japanese patients with CRPS. METHODS: We developed BPDS-J using a forward-backward method. We then assessed 22 patients with CRPS type 1 of the upper limb using BPDS-J, Brief Pain Inventory (BPI), Tampa Scale for Kinesiophobia (TSK), and a two-point discrimination threshold (TPD) on the middle finger. We investigated the internal consistency of BPDS-J and the correlation between BPDS-J and clinical outcomes as a concurrent validity measure. RESULTS: BPDS-J had good internal consistency (Cronbach's α = 0.73) and was significantly correlated with the TPD ratio (r = 0.65, adjusted p = 0.01) and TSK (r = 0.51, adjusted p = 0.04). CONCLUSIONS: BPDS-J has good internal consistency and concurrent validity for assessing body perception disturbance in Japanese patients with CRPS. Disturbed body perception may be worth evaluating when managing patients with CRPS using BPDS.

Injustice Experience Questionnaire, Japanese Version: Cross-Cultural Factor-Structure Comparison and Demographics Associated with Perceived Injustice.

OBJECTIVE: The Injustice Experience Questionnaire (IEQ) assesses injury-related perceived injustice. This study aimed to (1) develop a Japanese version (IEQ-J), (2) examine its factor structure, validity, and reliability, and (3) discover which demographic variable(s) positively contributed to prediction of IEQ-J scores. METHODS: Data from 71 patients (33 male, 38 female; age = 20+) with injury pain were employed to investigate factor structure by exploratory and confirmatory factor analyses. Concurrent validity was examined by Pearson correlation coefficients among the IEQ-J, Brief Pain Inventory (BPI), and Pain Catastrophizing Scale (PCS). Internal consistency was investigated by Cronbach's alpha, and test-retest reliability was indicated with intra-class correlations (ICCs) in 42 of 71 patients within four weeks. Relations between demographic variables and IEQ-J scores were examined by covariance analysis and linear regression models. RESULTS: IEQ-J factor structure differed from the original two-factor model. A three-factor model with Severity/irreparability, Blame/unfairness, and Perceived lack of empathy was extracted. The three-factor model showed goodness-of-fit with the data and sufficient reliability (Cronbach's alpha of 0.90 for total IEQ-J; ICCs = 0.96). Pearson correlation coefficients among IEQ-J, BPI, and PCS ranged from 0.38 to 0.73. Pain duration over a year (regression coefficient, 11.92, 95%CI; 5.95-17.89) and liability for injury on another (regression coefficient, 12.17, 95%CI; 6.38-17.96) predicted IEQ-J total scores. CONCLUSIONS: This study evidenced the IEQ-J's sound psychometric properties. The three-factor model was the latter distinctive in the Japanese version. Pain duration over a year and injury liability by another statistically significantly increased IEQ-J scores.

Socioeconomic value of intervention for chronic pain.

PURPOSE: The purpose of this study was to examine the cost-effectiveness of pain treatments in two pain centers in Japan. METHODS: The study population comprised 91 patients receiving various treatments for chronic pain, which were divided into three categories: (1) medication, (2) medication + nerve block, and (3) other modalities (exercise and/or pain education). Pain was assessed using the Pain Disability Assessment Scale (PDAS) score, Hospital Anxiety and Depression Scale (HADS) score, Pain Catastrophizing Scale (PCS) score, and EQ-5D score. First, the reliability of the EQ-5D score first assessed by evaluating the correlation this score with those of the other pain-related evaluation instruments, and then the cost effectiveness of the pain treatments was evaluated. Evaluation of medical costs was based on data provided from the Management Services of the hospital, which in turn were based on national health scheme medical treatment fees. The quality-adjusted life year (QALY) value was calculated from the EQ-5D score, converted to 12 months, and then used for cost-benefit analysis along with medical treatment fees. RESULTS: According to the recent IASP classification, more patients had chronic neuropathic pain (41) than chronic primary pain (37 patients) or chronic musculoskeletal pain (27 patients). There was a significant correlation between the EQ-5D score and the PDAS, HADS, and PCS scores, which demonstrated the reliability of the EQ-5D score. Significant improvement in the HADS, PCS, and EQ-5D scores was noted after 3 months of pain treatment. Calculation of the cost-effectiveness based on the estimated annual medical treatment cost and QALY revealed a mean value of US $45,879 ± 103,155 per QALY (median US $16,903), indicating adequate socioeconomic utility. CONCLUSION: Based on our results, the EQ-5D is reliable for evaluating chronic pain in patients. The medico-economic balance was appropriate for all treatments provided in two comprehensive pain centers in Japan.

Pain-Related Brain Activity Evoked by Active and Dynamic Arm Movement: Delayed-Onset Muscle Soreness as a Promising Model for Studying Movement-Related Pain in Humans.

OBJECTIVE: To demonstrate delayed-onset muscle soreness (DOMS) is a suitable model for the study of movement-evoked pain, we attempted to identify brain regions specifically involved in pain evoked by active and dynamic movement under DOMS condition. SUBJECT: Twelve healthy volunteers METHODS: DOMS was induced in the left upper-arm flexor muscles by an eccentric elbow contraction exercise. Movement-evoked pain in the affected muscles was evaluated just before (day 0) and after (days 1-7 and 30) the exercise using a visual analog scale. Subjects underwent functional magnetic resonance imaging scans while performing repeated elbow flexion on day 2 (DOMS condition) and day 30 (painless condition). We compared brain activity between the DOMS and painless conditions. RESULTS: Movement-evoked pain reached peak intensity on day 2 and disappeared by day 30 in all subjects. No subject felt pain at rest on either of these days. Contralateral primary motor cortex (M1), parietal operculum and bilateral presupplementary motor area (pre-SMA) showed greater activity during active and dynamic arm movement with DOMS than during the same movement without pain. There was no difference in activation of brain regions known collectively as the "pain matrix," except for the parietal operculum, between the two conditions. CONCLUSION: Active and dynamic movement with pain selectively evoked activation of M1, pre-SMA, and parietal operculum, as assessed using DOMS. Our results demonstrate that DOMS is a promising experimental model for the study of movement-evoked pain in humans.

A case of hypogonadotropic hypogonadism caused by opioid treatment for nonmalignant chronic pain.

We report a case of 42-year-old male patient with hypogonadotropic hypogonadism. He suffered from general fatigue and erectile dysfunction after the treatment with transdermal fentanyl for chronic pain by traffic injury. Endocrine examinations and hormone stimulating tests showed that he had hypogonadotropic hypogonadism. Brain magnetic resonance imaging (MRI) showed no abnormal findings, and he had no past history of accounting for acquired hypogonadotropic hypogonadism. Therefore, his hypogonadism was diagnosed to be caused by opioid treatment. Although opioid-induced endocrine dysfunctions are not widely recognized, this case suggests that we should consider the possibility of endocrine dysfunctions in patients with opioid treatment.

Brain imaging of mechanically induced muscle versus cutaneous pain.

This study aimed to investigate the differences in the brain responses between muscle versus skin pain, both of which were caused by tonic mechanical stimuli. Using local anesthesia (LA), we induced muscle pain without any accompanying cutaneous sensation. Subjects underwent functional magnetic resonance imaging while tonic pressure was applied to the right calf under the following four conditions: (1) non-painful pressure without LA (causing mechanoreceptive skin and muscle stimulation); (2) painful pressure without LA (causing nociceptive skin stimulation and mechanoreceptive skin and muscle stimulation); (3) non-painful pressure with LA (causing mechanoreceptive muscle stimulation); (4) painful pressure with LA (causing nociceptive and mechanoreceptive muscle stimulation). Although there was no brain region specifically activated by nociceptive muscle stimuli, activation in the following regions was observed specifically during nociceptive muscle stimuli: anterior midcingulate cortex, anterior and posterior insular cortex, lentiform nucleus, thalamus, pre-supplementary motor area, dorsolateral prefrontal cortex, and inferior parietal lobule. This indicates that there is no region specific for muscle pain but activation pattern or network specific for muscle pain. Furthermore, secondary somatosensory cortex (S2) was found to be responsive to cutaneous pain, not muscle pain, because S2 was specifically activated by nociceptive cutaneous stimuli.

[Phantom limb pain originates from dysfunction of the primary motor cortex].

Accumulated knowledge indicates that phantom limb pain is a phenomenon of the central nervous system that is related to plastic changes at several levels of the nervous systems. Especially, reports using patients with neuropathic pain clearly indicate the sensorimotor cortex as underlying mechanisms of phantom limb and its pain. Here, we focus the notion that limb amputation or deafferentation results in plasticity of connections between the brain and the body, and that the cortical motor representation of the missing or deafferented limb seemingly disappears. Meanwhile, the sensory representation of the limb does not disappear and thereby patients feel phantom limbs. We propose that dissociation between motor and sensory representations in the primary motor cortex induces pathologic pain and reconcile of sensorimotor integration of the limb would alleviate pain, on the basis of our neurorehabilitation approaches and artificial neuromodulation strategies.

Complex regional pain syndrome (CRPS) impairs visuospatial perception,whereas post-herpetic neuralgia does not: possible implications for supraspinal mechanism of CRPS.

INTRODUCTION: Complex regional pain syndrome (CRPS) patients show impaired visuospatial perception in the dark, as compared to normal patients with acute nociceptive pain. The purpose of this study is 2-fold: (i) to ascertain whether this distorted visuospatial perception is related to the chronicity of pain, and (ii) to analyse visuospatial perception of CRPS in comparison with another neuropathic pain condition. MATERIALS AND METHODS: We evaluated visual subjective body-midline (vSM) representation in 27 patients with post-herpetic neuralgia (PHN) and 22 with CRPS under light and dark conditions. A red laser dot was projected onto a screen and moved horizontally towards the sagittal plane of the objective body-midline (OM). Each participant was asked to direct the dot to a position where it crossed their vSM. The distance between the vSM and OM was analysed to determine how and in which direction the vSM deviated. RESULTS: Under light condition, all vSM judgments approximately matched the OM. However, in the dark, CRPS patients, but not PHN patients, showed a shifted vSM towards the affected side. CONCLUSION: We demonstrated that chronic pain does not always impair visuospatial perception. The aetiology of PHN is limited to the peripheral nervous system, whereas the distorted visuospatial perception suggests a supraspinal aetiology of CRPS.