An Open-Label Pilot Study Investigating Noninvasive High-Frequency Peripheral Nerve Fiber Stimulation in Chronic Pain.

OBJECTIVE: Providing sustained and effective treatment via the peripheral nervous system for the management of chronic pain is challenging. Application of noninvasive high-frequency stimulation at or near the painful area may benefit those with chronic pain. This open-label pilot survey examined the impact of this stimulation on pain intensity, activities of daily living, functional capacity, and medication consumption after 2 weeks of treatment. METHODS: Stimulation was administered at home using the summation of two high-frequency sinusoidal alternating signals at 3858 and 3980 Hz delivered between two electrodes placed directly over one or two locations of pain. Individuals completed a survey after 2 weeks to assess pain, activities of daily living (ADL), pain medication consumption, quality of life (QoL), mood, sleep, functional outcomes, and satisfaction. RESULTS: 463 individuals (372 males; 91 females) retuned the completed survey after 2 weeks of treatment. Pain and ADL scores significantly improved at follow-up compared with baseline (pain mean difference: 3.05; 95% confidence interval [CI]: 2.86, 3.24; ADL mean difference: 1.82; 95% CI: 1.60, 2.04). Corresponding improvements in QoL, sleep, mood, functional outcomes, and satisfaction were noted. On average, 8.00 ± 11.11 hours of pain relief were reported with 54% experiencing reductions in pain medication consumption. 98% would use the stimulation in the future. CONCLUSION: Two weeks of noninvasive high-frequency peripheral nerve fiber stimulation appeared to confer positive effects in individuals with chronic pain. Future research employing a control group/arm is needed to establish the long-term impact of this bioelectric technique in specific pain cohorts.

Ionizing Radiation Dose Exposure to the Ocular Region of Pain Physicians During C-arm Guided Pain Interventions.

BACKGROUND: The growth of interventional pain medicine in recent years has resulted in more procedures being carried out under fluoroscopic guidance. The proximity of the pain physician (PP) to ionization radiation (IR) potentially increases the risk of radiation exposure to the ocular region. A European directive has reduced the limits of occupational ocular dose 7.5-fold. OBJECTIVES: The objectives of this study are to quantify the typical IR exposure in the ocular region of PP and to compare it to recommended international guidelines. STUDY DESIGN: Three consultants involved in the pain unit service were enrolled in the study to reflect the dose implications involved with different caseloads, training obligations, and procedure types. All 3 consultants were experienced primary operators. SETTING: The study was undertaken at the pain management suite in the South Infirmary Victoria University Hospital (SIVUH). Annually, this unit performs 2,800 fluoroscopic guide pain procedures. METHODS: Thermoluminescent dosimeters (TLDs) calibrated to measure eye lens doses [Hp (0.07)] and whole-body doses (WBDs) were fitted to 3 pain consultants while they undertook imaging-guided pain procedures using mobile C-arm fluoroscopy over a 3-month period. The duration of radiation exposure, screening time (seconds), and procedure type were recorded. Radiation dose was calculated to estimate the effective radiation dose to the ocular region using (i) dose-area product (DAP) in milliGray per centimeter squared (mGycm2) and (ii) Air Kerma (AK) values in mGy. RESULTS: IR doses were effectively recorded in 682 cases over 3 months and the data extrapolated. The estimated annual lens dose experienced by pain physicians performing fluoroscopy-guided procedures is less than the recommended international guidelines. A significant linear relationship between screening time and IR exposure was estimated (rs = 0.93, P < 0.01). LIMITATIONS: In many centers, including our own, fluoroscopy procedures are undertaken by nonconsultant staff. Therefore, a small single-center cohort recruiting experienced consultant staff and not including pain fellows or registrars/residents with varying levels of experience is a limitation. CONCLUSION: While IR to the ocular region was significantly less than the recommended European safety guidelines, the annual dose needs to be confirmed in pain physicians with a lesser degree of clinical experience. KEY WORDS: Ionizing radiation, ocular, radiation protection, pain medicine, interventional.

The Effect of Peripheral Neuromodulation on Pain from the Sacroiliac Joint: A Retrospective Cohort Study.

We report here a retrospective review of the longer-term results of peripheral neuromodulation in 12 patients with significant chronic sacroiliac joint pain who had previously failed multiple conservative and interventional pain therapies. To allow for the assessment of meaningful longer-term outcome, implants for all 12 patients had been in place for a minimum of 18 months to a maximum of 36 months prior to the formal review. Compared to the preimplantation baseline, the longer-term follow-up revealed a significant and sustained reduction in visual analog scale pain scores from 8.7 ± 1.1 to 1.1 ± 1.0 (P < 0.001), with a 75% reduction in analgesia requirement, and improvement in pain impact on daily function from 94.1% ± 5.9% to 5.8% ± 6.0% (P < 0.001). These preliminary results merit a prospective randomized trial of peripheral neuromodulation.

Clinical Outcome Following Radiofrequency Denervation for Refractory Sacroiliac Joint Dysfunction Using the Simplicity III Probe: A 12-Month Retrospective Evaluation.

BACKGROUND: Sacroiliac joint syndrome (SIJ) is diagnosed in 10% to 25% of cases of lower back pain. The response to traditional radiofrequency (RF) denervation of the SIJ has being inconsistent. The Simplicity III RF probe (Neruotherm. Inc.) offers a novel treatment option. OBJECTIVE: To evaluate the long-term clinical outcome (12 months) refractory SIJ syndrome in terms of pain intensity and functional improvement. A 50% reduction in intensity pain intensity (VAS) at 12 months was deemed clinically significant. STUDY DESIGN: A 12-month retrospective observational evaluation all of adults treated with RF for refractory SIJ. SETTING: Chronic pain management center. METHODS: The medical records of all adults treated with this technique was retrospectively reviewed. The primary outcome was pain intensity scores (VAS) over a 12 months period; Secondary outcomes included Roland-Morris Functional scores (RMF), Brief Pain Inventory (BPI), general health assessment (Sf12), and patient satisfaction scores (GPI), which were recorded pre and post denervation. REULTS: Pain Intensity improved by 4.7 points compared to pre-treatment representing a 61% reduction in pain at 12 months (n=11, P < 0.001). Significant improvements in (a) RMF (P < 0.01, W2 = 0.63 (large effect size); (b) BPI (P < 0.001, W2 = 0.72 (strong effect size); and (c) Sf12 (P < 0.01) were noted. Overall patients were satisfied with the outcome (GPI = 77.7%). LIMITATIONS: The retrospective in nature of the study and the small sample size are limitations. As it was our policy to monitor the progress of the individuals since the introduction of this technique a reliable method of recording the baseline and outcome variables at each point of contact was in place. Access to a complete set of variables in all individuals over a 12-month period was therefore possible, which we feel contributes to the quality of the dataset. CONCLUSION: By creating a consistent radiofrequency lesion between the sacral foramen and the SIJ will reliably capture the innervation to the SIJ with significant long-term clinical improvement. This technique should be considered earlier in the treatment algorithm of individuals suffering from SIJ symptoms.

Psychological Reactions and Persistent Facial Pain following Enucleation.

Background. Enucleation is a psychologically and physically traumatic event associated with chronic pain. It would be desirable to better predict which patients will have pain after surgery. Methods. A cross-sectional postal questionnaire study of adults undergoing enucleation captured the demographic details, Pain Quality Assessment Scale (PQAS), Pain Catastrophizing Scale (PCS), and the Facial Pain Assessment questionnaire. Patients were classified as suffering from chronic pain if they reported a pain score of >1 out of 10 on the numerical pain score (NRS). Results. Seventeen of 60 adults participated in the study. 47% of patients reported chronic pain (mean pain score = 1.4 ± 0.7, n = 17); 25% experienced pain daily. No difference in age, surgical side, reason for surgery, or the duration of time since the surgery was noted. All patients had low PQAS scores and 50% of individuals with persistent pain were concerned about their facial appearance. There was no significant difference in the level of catastrophization noted in patients with or without pain or between the subgroups (rumination, magnification, or helplessness). Conclusions. Although persistent pain following enucleation affected a significant number of patients, the pain intensity was mild. Enucleation influenced the physical perception some individuals had of themselves.

Multivariate prognostic modeling of persistent pain following lumbar discectomy.

BACKGROUND: Persistent postsurgical pain (PPSP) affects between 10% and 50% of surgical patients, the development of which is a complex and poorly understood process. To date, most studies on PPSP have focused on specific surgical procedures where individuals do not suffer from chronic pain before the surgical intervention. Individuals who have a chronic nerve injury are likely to have established peripheral and central sensitization which may increase the risk of developing PPSP. Concurrent analyses of the possible factors contributing to the development of PPSP following lumbar discectomy have not been examined. OBJECTIVE: The aim of this study is to identify risk and protective factors that predict the course of recovery following lumbar discectomy and to develop an easily applicable preoperative multivariate prognostic model for the occurrence of PPSP in this patient cohort. STUDY DESIGN: A prospective study of elective lumbar discectomy with a 3 month follow-up. SETTING: University setting in Ireland. METHODS: All ASA I-II patients, (n = 53, 18-65 years old), undergoing elective lumbar discectomy at a single institute were included and followed for a 3 month period postsurgery. Preoperative potential predictors were collected: age, gender, pain intensity (McGill score, visual analog scale [VAS], Present Pain Intensity), degree of dysfunction (Roland-Morris Function score), psychological status (pain catastrophizing, anxiety, and depression scores), health-related quality of life (SF-36), quantitative sensory testing (QST), inflammatory biomarkers, and a genetic pain profile. The proposed primary outcome was significant pain reduction (VAS > 70%) 3 months following surgery compared to the preoperative pain intensity. RESULTS: A final prediction model was obtained using a multivariate logistic regression in combination with bootstrapping techniques for internal validation. Twenty (37.7%) patients developed PPSP. Independent predictor factors included age (odds ratio [OR] = 1.0 per year), present pain intensity (OR = 0.6), and degree of dysfunction (OR = 1.2). The concordance index C (.658) supports a good monotonic association (where perfect prediction is 1) and the Akaike's information criteria indicated a good fit of the model. Inclusion of additional measured parameters (QST, biomarker, or genotyping) did not improve the model. LIMITATIONS: Before this internally validated model can be integrated into clinical practice, and used for patient counselling and quality assurance purposes, external validation studies are necessary. CONCLUSIONS: We demonstrated that the occurrence of PPSP can be predicted using a small set of variables easily obtained at the preoperative visit. This a prediction rule that could further optimize perioperative pain treatment and reduce attendant complications by allowing the preoperative classification of surgical patients according to their risk of developing PPSP.

Spinal cord stimulation: the clinical application of new technology.

The use of neuromodulation for pain relief is among the fastest-growing areas of medicine, involving many diverse specialties and impacting on hundreds of thousands of patients with numerous disorders worldwide. As the evidence of efficacy improves, the interest in spinal cord stimulation (SCS) will increase because it is minimally invasive, safe, and a reversible treatment modality with limited side effect profile. While the mechanism of action evades complete understanding, the technological improvements have been considerable and current neuromodulation developments have been coupled with the rapid growth of the neuromodulation device industry resulting in the development of the next-generation neuromodulation systems. The development, the newest technicaliti and the future for the clinical application of spinal cord stimulation (SCS) are reviewed here.

Peripheral nerve stimulation of the thoracic paravertebral plexus for chronic neuropathic pain.

Persistent post surgical pain is reported in 70% of patients following thoracotomy and mastectomy. This pain is often neuropathic in nature and occasionally it is refractory to traditional medical and interventional management. Neurostimulation of peripheral nerves can be a highly effective clinical modality for the management of neuropathic pain. The placement of a percutaneously sited electrode in the thoracic paravertebral plexus offers a new and novel mode of managing refractory thoracic neuropathic pain. We present 2 cases that demonstrate the effectiveness of this intervention in the long-term management of this clinical dilemma. The first case presented is that of a 61-year-old female, with unilateral neuropathic pain for 6 years following mastectomy refractory to traditional interventions. Targeted field stimulation of the thoracic paravertebral plexus resulted in significant improvement for 12 years. The second case is that of a 65-year-old male, with Type II diabetes with neuropathic thoracic pain for 6 years following multiple rib fractures (T4-T7) who responded positively to neurostimulation of the thoracic paravertebral plexus. Both of these cases demonstrate a relative reduction in pain intensity (> 80%), the elimination of oral analgesics, and improved functionality directly related to the novel use of this intervention. Effective and reproducible pain relief is achieved by specifically using a low frequency (10 Hz) and low amplitude (2 mA) stimulation technique. Equally important is that these cases highlight the increased risk of inadvertent pleural puncture with the development of a pneumothorax that can be associated with this intervention. Possible clinical, investigative and equipment modifications that need to be considered are discussed. The limitations include only 2 case reports, considered as the lowest level of evidence available in the era of evidence-based medicine, and lack of utilization of multiple other modalities of treatments utilized in managing neuropathic pain. In conclusion, these cases demonstrate the effectiveness of peripheral nerve stimulation of the thoracic paravertebral plexus in the long-term management of refractory neuropathic pain. They also serve to underline the importance of clinical awareness in order to improve patient safety.

Association between preoperative magnetic resonance imaging, pain intensity and quantitative sensory testing in patients awaiting lumbar diskectomy.

INTRODUCTION: Magnetic resonance imaging (MRI) offers important information regarding the morphology, location and size of a herniated disc, which influences the decision to offer lumbar diskectomy (LD). This study aims to examine the association between clinical neurophysiologic indices including pain intensity and quantitative sensory testing (QST), and the degree of lumbar nerve root compromise depicted on magnetic resonance (MR) in patients awaiting LD. METHODS: With institutional ethical approval, 16 patients (American Society of Anaesthesiologists Grades I-II, 18-65 years) with radicular pain for greater than 3 months undergoing elective LD were studied. Preoperative pain was assessed using (i) a visual analogue scale measuring pain intensity at rest and with movement and (ii) by quantifying pain sensory thresholds (St), pain perception thresholds (PPt), and pain tolerance threshold (PTt) using QST. MR images were independently graded by two radiologists blinded to the clinical data using the Pfirrmann grading system. Statistical analyses using Student's t-tests and Pearson's correlation were preformed where appropriate. RESULTS: This study showed that: (i) findings on MR imaging corresponded with the symptomatic side and distribution of the pain; (ii) the degree of nerve root compromise, detected on MRI correlated with increased pain intensity at rest; and (iii) QST identified a trend towards higher St, PPt and PTt in patients with higher Pfirrmann grades. CONCLUSIONS: The Pfirrmann grading system of nerve root compromise may be clinically useful preoperatively as a method of identifying individuals who would benefit most from LD. However, additional studies with greater patient numbers and longer follow-up are required to definitively confirm the findings of this study.

A Randomised, Placebo-controlled Trial of the Effects of Preoperative Pregabalin on Pain Intensity and Opioid Consumption following Lumbar Discectomy.

BACKGROUND: Pregabalin has been shown to have analgesic effect in acute pain models. The primary objective was to examine the efficacy a single dose of pregabalin, would have on morphine consumption following lumbar discectomy. METHODS: With ethical approval a randomized, placebo-controlled prospective trial was undertaken in 32 patients (ASA I-II, 18-65 years) with radicular low back pain for > 3 months undergoing elective lumbar discectomy. Patients received either oral pregabalin 300 mg (PG Group) or placebo (C Group) one hour before surgery. Pain intensity, the accumulative morphine consumption and adverse effects were recorded for 24 hours following surgery. Functional, psychological and quantitative sensory testing were also assessed. RESULTS: Fourteen patients out of the 32 recruited were randomized to receive pregabalin. Morphine consumption was reduced (absolute difference of 42.3%) between groups with medium effect size. (Mann-Whitney; U = 52.5, z-score= 2.84, P = 0.004, r = 0.14). This was not associated with a significant difference in the incidence of adverse effects between the two groups. The median pain intensity (VAS) on movement was not significantly different between groups. CONCLUSIONS: A single pre-operative dose of pregabalin (300 mg) did not result in a reduction in pain intensity compared to placebo in this patient cohort but the significant reduction in morphine consumption suggests that a fixed peri-operative dosing regime warrants investigation.