Relationships Among Pain Quality, Pain Impact, and Overall Improvement in Patients with Postherpetic Neuralgia Treated with Gastroretentive Gabapentin.

OBJECTIVE: To determine the effect of gastroretentive gabapentin (G-GR) and describe relationships among pain quality, pain impact, and overall-improvement scores in patients with postherpetic neuralgia (PHN). METHODS: Analyses of integrated data from two Phase 3 studies in which PHN patients received once-daily G-GR 1,800 mg (n = 356) or placebo (n = 363). Neuropathic pain scale (NPS) and brief pain inventory (BPI) were completed at baseline and Week 10; patients' global impression of change (PGIC) at Week 10. Regression analyses described relationships among changes in the NPS, BPI, and PGIC scores. RESULTS: Compared with placebo, G-GR patients had significant reductions from baseline in individual NPS measures except cold pain (P < 0.05); composite NPS scores (P ≤ 0.003); BPI pain scores (P < 0.05); three individual (mood, sleep, and enjoyment of life) and the average of BPI interference scores (P < 0.05). Clinically significant improvements in BPI interference scores (except walking ability) were positively correlated with reductions in BPI and NPS pain (except dull and cold pain), and with improvements on the PGIC. Reductions in pain qualities at Week 2, especially in NPS pain intensity, were significant (P ≤ 0.0001) predictors of improvements in three BPI interference scores, total NPS score, and PGIC. CONCLUSIONS: For patients with PHN, G-GR provided significant improvements in multiple measures of pain quality and pain-related functional impairment. There was a positive correlation between pain relief and improvement in patient function, with reduction in pain intensity among predictors of improvements in patients' lives. Such comprehensive analyses give an insight into numerous factors that may contribute to better management of PHN.

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.

Pulsed electromagnetic fields to reduce diabetic neuropathic pain and stimulate neuronal repair: a randomized controlled trial.

OBJECTIVE: To determine whether repetitive and cumulative exposure to low-frequency pulsed electromagnetic fields (PEMF) targeting painful feet can reduce neuropathic pain (NP), influence sleep in symptomatic diabetic peripheral neuropathy (DPN), and influence nerve regeneration. DESIGN: Randomized, double-blind, placebo-controlled parallel study. SETTING: Sixteen academic and clinical sites in 13 states. PARTICIPANTS: Subjects (N=225) with DPN stage II or III were randomly assigned to use identical devices generating PEMF or sham (placebo) 2 h/d to feet for 3 months. INTERVENTIONS: Nerve conduction testing was performed serially. MAIN OUTCOME MEASURES: Pain reduction scores using a visual analog scale (VAS), the Neuropathy Pain Scale (NPS), and the Patient's Global Impression of Change (PGIC). A subset of subjects underwent serial 3-mm punch skin biopsies from 3 standard lower limb sites for epidermal nerve fiber density (ENFD) quantification. RESULTS: Subjects (N=225) were randomized with a dropout rate of 13.8%. There was a trend toward reductions in DPN symptoms on the PGIC, favoring the PEMF group (44% vs 31%; P=.04). There were no significant differences between PEMF and sham groups in the NP intensity on NPS or VAS. Twenty-seven subjects completed serial biopsies. Twenty-nine percent of PEMF subjects had an increase in distal leg ENFD of at least 0.5 SDs, while none did in the sham group (P=.04). Increases in distal thigh ENFD were significantly correlated with decreases in pain scores. CONCLUSIONS: PEMF at this dosimetry was noneffective in reducing NP. However neurobiological effects on ENFD, PGIC and reduced itching scores suggest future studies are indicated with higher dosimetry (3000-5000 G), longer duration of exposure, and larger biopsy cohort.