Rui V. Duarte

A systematic literature review of psychological characteristics as determinants of outcome for spinal cord stimulation therapy

&NA; Psychological factors are deemed important when considering patients for suitability for Spinal Cord Stimulation (SCS). However, there is to date no consensus on which psychological characteristics or tests to undertake. This review analyses the literature to determine findings concerning the psychological characteristics observed and their impact on SCS efficacy for chronic pain. A search in the databases Cochrane, EBSCOhost (CINAHL, MEDLINE, PsycINFO and PsycARTICLES) and a hand search of reference lists from selected articles were performed, resulting in nine relevant articles. The Minnesota Multiphasic Personality Inventory was the most commonly used tool for assessing psychological factors. Only one study used a semi‐structured interview instead of questionnaires. Studies lacked long term followup. Depression was identified in six studies as a factor that reduces efficacy, also as a characteristic that can improve after successful SCS by two studies. One study did not include patients with depression, due to previous research indicating depression as a contra‐indication. Hypochondriasis and hysteria had conflicting results for prediction of efficacy. Mania was predicted by only two studies as a positive indicator for success. Further long term studies of psychological factors on outcome from SCS are needed.

Neuropathic pain in osteoarthritis: A review of pathophysiological mechanisms and implications for treatment

OBJECTIVES Osteoarthritis (OA) is the leading cause of musculoskeletal pain and functional disability worldwide, affecting a growing number of individuals in the western society. Despite various conservative and interventional treatment approaches, the overall management of the condition is problematic, and pain-the major clinical problem of the disease-remains sub-optimally controlled. The objectives of this review are to present the pathophysiologic mechanisms underlying the complexity of pain in OA and to discuss the challenges for new treatment strategies aiming to translate experimental findings into daily clinical practice. METHODS A narrative literature review of studies investigating the existence of a neuropathic component in OA pain was conducted. We searched PubMed, Embase and Scopus for English language publications. A hand-search of reference lists of relevant studies was also performed. RESULTS Recent advances have shed additional light on the pathophysiology of osteoarthritic pain, highlighting the contribution of central pain pathways together with the sensitisation of peripheral joint receptors and changes of the nociceptive process induced by local joint inflammation and structural bone tissue changes. Thus, a neuropathic pain component may be predominant in individuals with minor joint changes but with high levels of pain refractory to analgesic treatment, providing an alternative explanation for osteoarthritic pain perception. CONCLUSION A growing amount of evidence suggests that the pain in OA has a neuropathic component in some patients. The deeper understanding of multiple mechanisms of OA pain has led to the use of centrally acting medicines that may have a benefit on alleviating osteoarthritic pain. The ineffective pain management and the increasing rates of disability associated with OA mandate for change in our treatment paradigm.

Intrathecal inflammatory masses: is the yearly opioid dose increase an early indicator?

Objectives:  The objective of this study is to investigate the association between intrathecal drug, flow rate, drug concentration, and drug dose with the formation of intrathecal inflammatory masses.

Long-term intrathecal drug administration for chronic nonmalignant pain.

Background: Chronic pain of nonmalignant origin requires effective long-term treatments, as for many patients pain management will be necessary throughout the rest of their lives. Intrathecal drug delivery systems (IDDS) have become a recognized therapy for the management of severe and otherwise intractable chronic pain. However, it is still not clear whether this treatment can be effective for periods up to 10 years or longer, given the paucity of long-term follow-up. This study sought to examine the effectiveness of IDDS following an average of 13 years postimplantation. Methods: Twenty patients participated in a longitudinal study with an average follow-up of 13.5 years (range: 10.4 to 17.9) after IDDS implantation. Investigation was carried out by means of a questionnaire before IDDS and after an average of 4 and 13 years of IDDS therapy. Assessment of pharmacological data and complications/side effects was performed. Results: Statistically significant improvements between baseline and 4-year assessment were observed for the following sensory and psychosocial variables: pain intensity, pain relief, coping, self-efficacy, depression, quality of life, housework, mobility, sleep, and social life (all P<0.001). No statistically significant changes were detected between assessments at averages of 4 and 13.5 years. Conclusions: This study, with one of the longest follow-up intervals reported in the IDDS literature, shows that IDDS has the potential to be a life-long pain management solution in appropriately selected patients with chronic nonmalignant pain.

Hypogonadism and low bone mineral density in patients on long-term intrathecal opioid delivery therapy

Objectives This study aimed to investigate the hypothalamic-pituitary-gonadal axis in a sample of male patients undertaking intrathecal opioid delivery for the management of chronic non-malignant pain and the presence of osteopaenia and/or osteoporosis in those diagnosed with hypogonadism. Design Observational study using health data routinely collected for non-research purposes. Setting Department of Pain Management, Russells Hall Hospital, Dudley, UK. Patients Twenty consecutive male patients attending follow-up clinics for intrathecal opioid therapy had the gonadal axis evaluated by measuring their serum luteinising hormone, follicle stimulating hormone, total testosterone, sex hormone binding globulin and calculating the free testosterone level. Bone mineral density was measured by DEXA scanning in those patients diagnosed with hypogonadism. Results Based on the calculated free testosterone concentrations, 17 (85%) patients had biochemical hypogonadism with 15 patients (75%) having free testosterone <180 pmol/L and 2 patients (10%) between 180 and 250 pmol/L. Bone mineral density was assessed in 14 of the 17 patients after the exclusion of 3 patients. Osteoporosis (defined as a T score ≤−2.5 SD) was detected in three patients (21.4%) and osteopaenia (defined as a T score between −1.0 and −2.5 SD) was observed in seven patients (50%). Five of the 14 patients (35.7%) were at or above the intervention threshold for hip fracture. Conclusions This study suggests an association between hypogonadism and low bone mass density in patients undertaking intrathecal opioid delivery for the management of chronic non-malignant pain. Surveillance of hypogonadism and the bone mineral density levels followed by appropriate treatment may be of paramount importance to reduce the risk of osteoporosis development and prevention of fractures in this group of patients.

Type of Interventional Pain Procedure, Body Weight, and Presence of Spinal Pathology are Determinants of the Level of Radiation Exposure for Fluoroscopically Guided Pain Procedures

Abstract:  In the recent years new technology has led to the development of a bewildering array of imaging procedures. Yet, conventional radiography remains one of the most used tools to diagnose and to aid procedural interventions. Fluoroscopy guidance facilitates targeted drug delivery or radiofrequency directly to the area of pathology, a benefit that has to be balanced against the risks of radiation exposure. In this prospective observational survey of routine practice, dose area product (DAP) and screening time (ST) were recorded in 127 consecutive patients undergoing fluoroscopically guided spinal procedures along with other probable measures of potentially greater radiation exposure such as weight, type of spinal pathology, the ease of recognition of the anatomical landmarks, and the radiographic quality of the image in terms of contrast and graininess. The mean ST was 34 ± 27 seconds (range, 3 to 218 seconds), the mean DAP was 1.18 ± 1.08 Gy cm2 (range, 0.023 to 6.82 seconds). A correlation between weight and DAP was confirmed (r = 0.230, P < 0.05, Spearman’s correlation coefficient). Patients with spinal pathology (n = 33) had higher radiation exposure than those without (DAP median = 0.85, U = 978.00, P < 0.005, r = −0.28, Mann–Whitney test). The DAP values obtained compare favourably with the recommended doses for radiographs and other procedures, although they generally exceed the values for a chest X‐ray. ▪

Randomised, double-blind controlled trial by dose reduction of implanted intrathecal morphine delivery in chronic non-cancer pain

Objective This study aimed to investigate the efficacy of intrathecal morphine in the long term by hypothesising that a reduction of the intrathecal opioid dose following long-term administration would increase the level of pain intensity. Design Randomised, double-blind, controlled, parallel group trial. Setting Department of Pain Management, Russells Hall Hospital, Dudley, UK. Participants 24 patients with non-cancer pain implanted with morphine reservoirs were assessed for eligibility. Interventions Participants were randomly allocated to one of two parallel groups in which one of the groups had no change in morphine dose and the other group had a small reduction (20%) in dosage every week during a 10-week follow-up. Outcome Primary outcomes were visual analogue scale (VAS) pain score change and withdrawal from the study due to lack of efficacy. Results 9 of the patients assessed for eligibility declined to participate in the study. 15 patients were randomised to control (n=5) or intervention (n=10) and included in an intention-to-treat analysis. Owing to worsening of pain, seven patients withdrew from the study prematurely. None knew prior to withdrawal which arm of the study they were in, but all turned out to be in the dose-reduction arm. The calculation of dropout rates between groups indicated a significant statistical difference (p=0.026) and recruitment was ceased. The VAS change between baseline and the last observation was smaller in the control group (median, Mdn=11) than in the intervention group (Mdn=30.5), although not statistically significant, Z=−1.839, p=0.070; r=−0.47. Within groups, VAS was significantly lower at baseline (Mdn=49.5) than at the last observation (Mdn=77.5) for the reduction group, Z=−2.805, p=0.002; r=−0.627 but not for the control group (p=0.188). Conclusions This double-blind randomised controlled trial of chronic intrathecal morphine administration suggests the effectiveness of this therapy for the management of chronic non-cancer pain. However, owing to the small number of patients completing the study (n=8), further studies are warranted. Trial registration International Standard Randomised Controlled Trials Centre (ISRCTN 33733462).

Influence of a latent period in QALY anaylsis: Pilot study of intrathecal drug delivery systems for chronic non-malignant pain

Cost effectiveness of a treatment is an important factor in decision making in the United Kingdom. Preceding most interventional health care treatments there is a waiting period between decision and procedure where health care costs may be lessened. Intrathecal drug delivery systems (IDDS) are a recognised pain management therapy for chronic non-malignant pain. To our knowledge, the period of time between being placed on a waiting list for IDDS and the implant (latent period) has not been taken into consideration for cost effectiveness analysis. A retrospective longitudinal analysis of all pain related costs for a period no less than 4 years was undertaken by assessment of medical records of 12 consecutive patients implanted with IDDS for chronic non-malignant pain. The total cost of patient care for 2 years before latent, the latent period itself and 2 years after the implant of an IDDS was computed, according to the National Health Service tariff. An EQ-5D questionnaire was filled by all participants before and after IDDS implant. Total costs were converted to cost per day for comparison with latent period. The average duration of the latent period was 263 ± 176 days (range 3–489). The cost of conventional treatments during the pre-implant phase excluding the latent period was significantly higher (M = £5,005.86, SE = £918.56) compared with the costs of the same phase including the latent period (M = £4,086.35, SE = £959.09, t(11) = 2.23, p = 0.05, r = 0.56). The cost per day changed significantly over the different periods (χ2(2) = 24.00, p < 0.05). The variability and significantly lower costs of the latent period may influence cost effectiveness evaluations and consequently decision making, if not considered. Further studies analysing the influence of a latent period on the cost effectiveness of other treatments are warranted.

Brain activity modifications following spinal cord stimulation for chronic neuropathic pain: A systematic review

Spinal cord stimulation (SCS) is believed to exert supraspinal effects; however, these mechanisms are still far from fully elucidated. This systematic review aims to assess existing neurophysiological and functional neuroimaging literature to reveal current knowledge regarding the effects of SCS for chronic neuropathic pain on brain activity, to identify gaps in knowledge, and to suggest directions for future research.

Qualitative exploration of psychological factors associated with spinal cord stimulation outcome

Background and aim: Spinal cord stimulation (SCS) is a last resort treatment for chronic pain consisting of an implantable pulse generator connected to leads placed in the epidural space of the spinal cord. Effective in reducing chronic pain, however, efficacy has been found to decrease over time. Psychological factors affecting outcome of SCS have been investigated through quantitative methods, but these have failed to provide confident predictors. We aimed to investigate via a qualitative approach, the experience of SCS following 1 year of therapy. Methods: Thirteen chronic non-cancer pain participants were interviewed. All participants had been trialled with SCS. The majority had gone on to full implantation with varying degrees of pain relief. Thematic analysis was employed to analyse the data from the interviews. Results: Interviews resulted in findings that previous quantitative studies had failed to uncover. Two emergent core themes surfaced: ‘coping with pain’ and ‘SCS treatment’. The effect of emotion upon coping was recurrent. Participants divided the SCS experience into information provision, independence and unexpected experiences. Conclusion: The findings provide context for the patients’ experience of SCS. This research suggests that improved preparation prior to SCS including information provision, CBT and contact with expert patients may be of value.