A brief, high-dose remifentanil infusion partially reverses neuropathic pain in a subgroup of post herpetic neuralgia patients.

Mechanism-based therapy for chronic pain is desperately needed. Recent basic science research demonstrated that remifentanil can reverse long-term potentiation at C-fiber synapses in the dorsal horn of rats. In this exploratory, single group study, patients with chronic post-herpetic pain were treated with a single, one-hour, high-dose remifentanil infusion. The mean overall change of pain intensity seven days after treatment was -18 (-7.5; -28.5, 95%CI, p<0.001) points on the numeric rating scale (0-100) (-33 (±11) points amongst responders only). Eleven of 20 patients responded to treatment (≥30% reduction in pain), the mean relative reduction in pain from baseline amongst responders was 61.0%. These promising preliminary results suggest that a mechanism-based reversal of chronic pain may be impending.

Peripheral nerve field stimulation (PNFS) in chronic low back pain: a prospective multicenter study.

OBJECTIVES: The goal of this study was to evaluate the long-term efficacy and safety of peripheral nerve field stimulation (PNFS) for chronic low back pain (cLBP). MATERIALS AND METHODS: In this prospective, multicenter observational study, 118 patients were admitted to 11 centers throughout Austria and Switzerland. After a screening visit, all patients underwent a trial stimulation period of at least seven days before implantation of the permanent system. Leads were placed in the subcutaneous tissues of the lower back directly in the region of greatest pain. One hundred five patients were implanted with a permanent stimulating system. Patients' evaluation of pain and functional levels were completed before implantation and one, three, and six months after implantation. Adverse events, medication usage, and coverage of the painful area and predictive value of transcutaneous electrical nerve stimulation (TENS) were monitored. RESULTS: All pain and quality-of-life measures showed statistically significant improvement during the treatment period. These included the average pain visual analog scale, the Oswestry Disability Questionnaire, the Becks Depression Inventory, and the Short Form-12 item Health survey. Additionally, medication usage with opioids, nonsteroidal anti-inflammatory drugs, and anti-convulsants showed a highly significant reduction. Complications requiring surgical intervention were reported in 9.6% of the patients. The degree of coverage of painful areas seems to be an important criterion for efficacy of PNFS, whereas TENS is presumably no predictor. CONCLUSIONS: This prospective, multicenter study confirms that PNFS is an effective therapy for the management of cLBP. Significant improvements in many aspects of the pain condition were measured, and complications were minimal.

Treatment of neuropathic pain with the capsaicin 8% patch: Quantitative sensory testing (QST) in a prospective observational study identifies potential predictors of response to capsaicin 8% patch treatment.

Background and aims Peripheral neuropathic pain (PNeP) is a chronic and disabling condition for which no predictors of response to treatment have yet been identified. Clinical studies show that while many patients with PNeP respond positively to treatment with the capsaicin 8% patch, others do not. This study used quantitative sensory testing (QST) to determine whether any patient characteristics can predict response to treatment with the capsaicin 8% patch. Methods This was a prospective, non-placebo-controlled, observational study. Patients used the Visual Analogue Scale (VAS) to assess their pain at baseline and then on Days 1, 7-10 (from here referred to as Day 7/10), 28 and 84 following treatment with the capsaicin 8% patch. QST was undertaken at the same timepoints on the painful area at the region of maximum PNeP and on a contralateral, control area. In addition, the size of the painful area was assessed at baseline and Days 7/10, 28 and 84. Results A total of 57 patients were treated. Among 54 evaluable patients, 19 (35.2%) achieved a ≥30% reduction in VAS pain score at Day 7/10 post-treatment compared with baseline - these were defined as 'responders'. Analysis of the QST data showed that the PNeP area in responders, but not in non-responders, had a significantly lower pressure pain threshold compared with the control area at baseline (median 320 kPa vs. 480 kPa, respectively; p = .004). Furthermore, non-responders had approximately three times greater degree of allodynia at baseline compared with responders across tests using brush, cotton wool and Q-tip. These differences were significant for tests using brush and cotton wool (p = .024 and p = .046, respectively) and approached significance in the test using Q-tip (p = .066). Following treatment with the capsaicin 8% patch, responders showed a trend towards a reduction in warm perception and also appeared to show normalization of the pinprick hyperalgesia at some stimulus levels. Responders to therapy had significantly greater reductions than non-responders in the size of the painful area at Day 28 (p = .011) and Day 84 (p = .005) following treatment. However, both responders and non-responders had meaningful reductions in the size of the painful area compared with baseline values. Conclusions This study suggests that differences can be identified in the sensory profiles of patients with PNeP who respond to the capsaicin 8% patch and those who do not, specifically pressure pain threshold and degree of allodynia. Notably, both responders and non-responders experienced meaningful reductions in the size of the painful area following treatment. Implications The findings warrant further investigation in a larger number of patients and in prospective trials.

Subcutaneous target stimulation (STS) in chronic noncancer pain: a nationwide retrospective study.

Stimulation of primary afferent neurons offers a new approach for the control of localized chronic pain. We describe the results with a new neurostimulation technique, subcutaneous target stimulation (STS), for the treatment of chronic focal noncancer pain. STS applies permanent electrical stimulation directly at the painful area via a percutaneous-placed subcutaneous lead. We reported the clinical outcomes of 111 patients with focal chronic, noncancer pain treated with STS in this first nationwide, multicenter retrospective analysis. The indications for STS were low back pain (n = 29) and failed back surgery syndrome (back pain with leg pain) (n = 37), cervical neck pain (n = 15), and postherpetic neuralgia (n = 12). Pain intensity was measured on a numerical rating scale (NRS) before and after implantation. Data on analgesic medication, stimulation systems, position, and type of leads and complications were obtained from the patients' records. After implantation, the mean pain intensity improved by more than 50% (mean NRS reduction from 8.2 to 4.0) in the entire patient group (P = 0.0009). This was accompanied by a sustained reduction in demand for analgesics. In all the patients, the STS leads were positioned directly at the site of maximum pain. Lead dislocation occurred in 14 patients (13%), infections in 7 (6%), and in 6 cases (5%), lead fractures were observed. The retrospective data analysis revealed that STS effectively provided pain relief in patients suffering from refractory focal chronic noncancer pain and that STS is an alternative treatment option. Prospective controlled studies are required to confirm these retrospective findings. This article presents a new minimally invasive technique for therapy-resistant focal pain.