Neuropathic pain in cancer patients: mechanisms, syndromes, and clinical controversies

Lidocaine transdermal patches reduced pain intensity in neuropathic cancer patients already receiving opioid treatment

BACKGROUND

Limited efficacy has been observed when using opioids to treat neuropathic pain. Lidocaine patches reduce neuropathic pain in postherpetic neuralgia, but their benefits for cancer-related neuropathic pain remain unclear. This study aimed to investigate a treatment for cancer-related neuropathic pain.

METHODS

We conducted a prospective, open-label, single-arm study to assess the efficacy and safety of lidocaine transdermal patches in patients experiencing localized, superficial, neuropathic cancer pain. Terminal cancer patients already receiving opioid treatment participated in the 3-day study. The primary endpoint was pain intensity evaluated by the numerical rating scale (NRS). The secondary endpoints were the pain relief score and the quality of analgesic treatment.

RESULTS

The results showed a significant difference in the median NRS over 3 days (Kruskal-Wallis test, p < 0.0001). The median NRS pain intensity from Day 1 to Day 3 was 4.0 with 95% C.I. (3.3, 5.0), 3.0 (2.5, 3.5), and 2.6 (2.0, 3.0), respectively. The difference between the median NRS pain intensities of any 2 days was significant (Wilcoxon signed-rank test, p < 0.0001). The generalized estimating equation (GEE) estimation model showed significant differences between the NRS pain intensities on any 2 days. There was no significant difference in the pain relief score or the quality of analgesic treatment.

CONCLUSIONS

In this study, the 5% lidocaine transdermal patch reduced the NRS pain intensity in neuropathic cancer patients already receiving opioid treatment. Treatment of localized and superficial neuropathic pain caused by cancer was well tolerated and effective.

Vulvodynia - an evolving disease

Vulvodynia is a common vulval pain syndrome that occurs most commonly in reproductive women of all ages. It can, in some cases, present for the first time after menopause. Up to about 15% of adult women have had symptoms of vulvodynia, with 4-5% currently symptomatic. Since there are no specific tests for diagnosis, vulvodynia is a diagnosis of exclusion. The condition is commonly associated with other chronic pain disorders and can be exceedingly debilitating, resulting in sexual dysfunction, severe depression and/or anxiety. It can significantly impair quality of life. Goals for long-term team approach management should be discussed with the patient at the commencement of each intervention as effectiveness of therapy is not assured. Currently, there is no intervention that effects cure in all individuals and a combination of pharmacological therapy, psychotherapy and physiotherapy, reserving surgery as a last-line option, is the best option for treatment. There are no long-term data on how long women will have symptoms and, if resolved, what provokes symptoms again in the future, whilst correlation between the etiology of vulvodynia and efficacy of treatment is not known.

Tumors Provoke Inflammation and Perineural Microlesions at Adjacent Peripheral Nerves

Cancer-induced pain occurs frequently in patients when tumors or their metastases grow in the proximity of nerves. Although this cancer-induced pain states poses an important therapeutical problem, the underlying pathomechanisms are not understood. Here, we implanted adenocarcinoma, fibrosarcoma and melanoma tumor cells in proximity of the sciatic nerve. All three tumor types caused mechanical hypersensitivity, thermal hyposensitivity and neuronal damage. Surprisingly the onset of the hypersensitivity was independent of physical contact of the nerve with the tumors and did not depend on infiltration of cancer cells in the sciatic nerve. However, macrophages and dendritic cells appeared on the outside of the sciatic nerves with the onset of the hypersensitivity. At the same time point downregulation of perineural tight junction proteins was observed, which was later followed by the appearance of microlesions. Fitting to the changes in the epi-/perineurium, a dramatic decrease of triglycerides and acylcarnitines in the sciatic nerves as well as an altered localization and appearance of epineural adipocytes was seen. In summary, the data show an inflammation at the sciatic nerves as well as an increased perineural and epineural permeability. Thus, interventions aiming to suppress inflammatory processes at the sciatic nerve or preserving peri- and epineural integrity may present new approaches for the treatment of tumor-induced pain.

Unfolding Role of Erector Spinae Plane Block for the Management of Chronic Cancer Pain in the Palliative Care Unit

Pain adversely affects the quality of life in cancer patients. Although conventional oral analgesics and co-analgesics manage 80%-90% of pain, interventional pain management techniques may be useful in the management of cancer pain refractory to opioid analgesia or in patients unable to tolerate systemic opioids. Herein, we report three cases depicting the successful role of erector spinae plane block in our palliative care unit for the management of different chronic cancer pain.

Predictors of duloxetine response in patients with neuropathic cancer pain: a secondary analysis of a randomized controlled trial-JORTC-PAL08 (DIRECT) study

PURPOSE

Duloxetine has some effect against cancer neuropathic pain (CNP); however, predictors of duloxetine response are unclear. This study sought to identify predictors of duloxetine response in patients with CNP.

METHODS

Patients (N = 70) with CNP unresponsive to or intolerant of opioid-pregabalin combination therapy, with a brief pain inventory-short form (BPI-SF) Item 5 score (average pain) ≥ 4, and with a total hospital anxiety and depression scale score < 20, were randomized to a duloxetine or a placebo group. Multiple linear regression analysis was conducted to identify predictors of duloxetine response as a secondary analysis with the change in the average pain score on day 10 from day 0 as the dependent variable, and the following five covariates; baseline (day 0) average pain score, baseline opioid dose, continuation/discontinuation of pregabalin, and items 20 and 21 score of the short-form McGill pain questionnaire 2 (SF-MPQ-2) as independent variables.

RESULTS

Of the four domains (continuous pain, intermittent pain, neuropathic pain, and affective descriptors) score of SF-MPQ-2 on day 0, significant differences were observed in the neuropathic pain domain (p = 0.040) in change on the average pain between day 10 and day 0 in the duloxetine group. Multiple linear regression analysis revealed that patients with a high score for SF-MPQ-2 Item 21 (tingling pain) on day 0 had a significantly greater change in average pain between day 10 and day 0 (p = 0.046).

CONCLUSION

Patients with a high score for SF-MPQ-2 Item 21 might benefit more from duloxetine.

Effect of morphine and a low dose of ketamine on the T cells of patients with refractory cancer pain in vitro

The combination of morphine and ketamine is considered safe and efficacious in many patients. However, a considerable number of immunomodulatory effects have been reported to be produced by both morphine and ketamine. The aim of the present study was to assess the direct effect of morphine and a low dose of ketamine on the T cells of patients with refractory cancer pain in vitro. Venous blood was obtained from patients with refractory cancer pain and peripheral blood mononuclear cells were isolated using the Ficoll-Hypaque density gradient method. Anti-CD3 beads were used to isolate T cells by positive selection. Subsequently, the T cells were treated with vehicle, 200 ng/ml of morphine or 200 ng/ml of morphine + 100 ng/ml ketamine for 24 h, following which the cells were stimulated with anti-CD3 and anti-CD28. Flow cytometric analysis of CD3⁺ T cells, and interleukin (IL)-2 and interferon (IFN)-γ in the supernatant, reverse transcription-quantitative PCR analysis for the detection of IL-2 and IFN-γ and western blotting for the detection of p65 nuclear factor (NF)-κB were performed. In vitro, the CD4⁺ and CD8⁺ T cell counts, CD4⁺/CD8⁺ ratio, secretion of IL-2 and IFN-γ in the supernatant, mRNA expression levels of IL-2 and IFN-γ and expression of p65 NF-κB were significantly decreased following treatment with morphine and morphine + ketamine, compared with results in the control group (all P<0.05). However, there was no significant difference between treatment with morphine and that with morphine + ketamine. Treatment with morphine + ketamine in vitro decreased the immune functions of patients with refractory cancer pain, although the effect of treatment with morphine and a low dose of ketamine did not differ significantly from that with morphine treatment alone.

Adult Cancer Pain, Version 3.2019, NCCN Clinical Practice Guidelines in Oncology

In recent years, the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Adult Cancer Pain have undergone substantial revisions focusing on the appropriate and safe prescription of opioid analgesics, optimization of nonopioid analgesics and adjuvant medications, and integration of nonpharmacologic methods of cancer pain management. This selection highlights some of these changes, covering topics on management of adult cancer pain including pharmacologic interventions, nonpharmacologic interventions, and treatment of specific cancer pain syndromes. The complete version of the NCCN Guidelines for Adult Cancer Pain addresses additional aspects of this topic, including pathophysiologic classification of cancer pain syndromes, comprehensive pain assessment, management of pain crisis, ongoing care for cancer pain, pain in cancer survivors, and specialty consultations.

Neuropathic Pain in Patients with Cancer

We provide a detailed description of painful neural lesions in hospitalized patients with cancer. A total of 187 consecutive patients with cancer and pain, referred to the pain service of a cancer hospital, were evaluated within 24 hours by two neurologists and followed until discharge or death. Based on history, pain descriptors, physical examination, and radiological and electrophysiological studies, the pain was categorized as neuropathic in 103 patients. The most frequent sites of neurological injury were nerve roots, spinal cord and cauda equina, brachial and lumbosacral plexus, and peripheral nerves. There were no patients with pain caused by injury to the brain. In 93 of these patients, the pain was caused by ongoing neural injury, while, in 10 patients, the neural injury was old and stable. Within these two groups of patients with neuropathic pain, analgesic treatments differed. Prospective studies may determine if categorizing painful neurological injuries in cancer patients based on inferred pathophysiology is useful when deciding among different treatment options.

Sensory pain characteristics of vulvodynia and their association with nociceptive and neuropathic pain: an online survey pilot study

Supplemental Digital Content is Available in the Text.

Objectives:

To evaluate self-reported sensory pain scores of women with generalized vulvodynia (GV) and provoked vestibulodynia (PVD), characterize pain phenotypes, and assess feasibility of using the Internet for recruitment and data collection among women with vulvodynia.

Methods:

Descriptive online survey. Data collected using an online survey accessed via a link on the National Vulvodynia Association web site. Convenience sample, 60 women aged 18 to 45 years (mean = 32.7 ± 5.5); 50 white, 2 black/African American, 4 Hispanic/Latino, and 4 Native American/Alaskan Native, diagnosed with vulvodynia, not in menopause. Pain assessment and medication modules from PAINReportlt.

Results:

Women with GV (n = 35) compared to PVD (n = 25). Estimated mean pain sites (2.5 ± 1.4 vs 2.2 ± 1.0, P = 0.31), mean current pain (8.7 ± 1.4 vs 5.5 ± 4.0, P = 0.0008), worst pain (8.1 ± 1.8 vs 6.1 ± 3.6, P = 0.02), and least pain in the past 24 hours (4.4 ± 1.8 vs 2.0 ± 2.0, P < 0.0001). Average pain intensity (7.1 ± 1.2 vs 4.6 ± 2.9, P = 0.0003) on a scale of 0 to 10, mean number of neuropathic words (8.3 ± 3.6 vs 7.7 ± 5.0), and mean number of nociceptive words (6.9 ± 4 vs 7.5 ± 4.4). Nineteen (54%) women with GV compared to 9 (38%) with PVD were not satisfied with pain levels.

Conclusion:

Women with GV reported severe pain, whereas those with PVD reported moderate to severe pain. Pain quality descriptors may aid a clinician's decisions about whether to prescribe adjuvant drugs vs opioids to women with vulvodynia.

Pain: Persistent postsurgery and bone cancer-related pain

The generation of neuropathic pain is a complex dynamic process. Factors involved include one or more dysregulated sensory neural pathways; dysregulated activity of specific neurotransmitters, synapses, receptors and cognitive and emotional neural circuits; and the balance between degenerative and regenerative neural events. Risk factors include age, sex, cognition, emotions, genetic polymorphism, previous or ongoing chronic pain conditions and the use of certain drugs. Intense pain experienced before, during and after surgery is a risk factor for the development of central sensitization with consequent persistent postsurgery neuropathic pain. Blockade of N-methyl-D-aspartate receptors with appropriate drugs during and immediately after surgery may prevent persistent postsurgical pain. Most cancers, but particularly malignant metastases in bone, can induce persistent pain. Local factors including direct damage to sensory nerve fibres, infiltration of nerve roots by cancer cells and algogenic biological agents within the microenvironment of the tumour bring about central sensitization of dorsal horn neurons, characterized by neurochemical reorganization with persistent cancer pain. In this article, the clinical features, pathogenesis and principles of management of persistent postsurgery pain and cancer pain are briefly discussed.

Ketamine, as adjuvant analgesics for patients with refractory cancer pain, does affect IL-2/IFN-γ expression of T cells in vitro?: A prospective, randomized, double-blind study

BACKGROUND

Ketamine has been used as an analgesic adjuvant with morphine in the treatment of refractory cancer pain recently. But both morphine and ketamine have been reported to produce a number of immunomodulatory effects. The current study was performed to assess whether the concentration of ketamine, as adjuvant analgesics for patient with refractory cancer pain, was related to its effect on T cells interleukin-2 (IL-2)/interferon-γ (IFN-γ) expression in vitro.

METHODS

Peripheral blood mononuclear cells (PBMCs) were isolated from venous blood of patients with refractory cancer pain over a Ficoll-Hypaque density gradient. T cells were isolated from by positive selection using anti-CD3 beads. T cells were then treated with vehicle (C group), morphine (200 ng/mL, M group), morphine (200 ng/mL), and different dose of ketamine (100, 200, 1000 ng/mL; MK1, MK5, MK10 group) for 24 hours before stimulation with anti-CD3 and anti-CD28. Then supernatant IL-2 and IFN-γ protein analysis, quantitative reverse transcription polymerase chain reaction (RT-PCR) for IL-2 and IFN-γ were done.

RESULTS

There were no significant difference of supernatant IL-2 and IFN-γ among C group, M group, and MK1 group, but the mRNA of M group and MK1 group were decreased compared with C group (P < .05). Compared with C group, both of the supernatant protein and the mRNA of MK5 group and MK10 group were all significantly decreased (P < .01). Compared with M group, both of the supernatant protein and the mRNA of MK5 group and MK10 group were all decreased (P < .05), while supernatant IL-2 and the mRNA of MK10 group were significantly decreased (P < .01).

CONCLUSION

In conclusion, we confirmed that just as morphine, ketamine dose-dependently suppressed IL-2 and IFN-γ of activated T lymphocyte of patients with refractory cancer pain in vitro, but the inhibitory action of low dose ketamine could be neglected.

Do Vulvodynia TCM Patterns Differ by Pain Types? Beginning Evidence Supporting the Concept

INTRODUCTION

Vulvodynia affects a maximum of 14 million U.S. women; however, it has not been adequately characterized. Traditional Chinese Medicine (TCM) offers pattern diagnoses that may be considered vulvodynia phenotypes and may guide the development of more targeted treatments.

OBJECTIVES

In women with vulvodynia, to explore relationships between the TCM patterns and pain.

DESIGN/METHODS

In an exploratory study, 36 women diagnosed with vulvodynia had a TCM assessment and completed the Short Form McGill Pain Questionnaire (SF-MPQ).

RESULTS

All 36 women were diagnosed with one of the two TCM patterns (excess heat [n = 28] or excess cold [n = 8]). Although not statistically significant, (1) the excess heat pattern group had a higher mean sensory score (14.4 ± 6.0) and mean affective pain score (4.1 ± 2.8) (more pain) compared with the mean sensory score (13.3 ± 5.9) and mean affective score (3.3 ± 1.8) of the excess cold pattern group; (2) there was a higher mean score for neuropathic sensory descriptors in the excess heat pattern group (1.55 ± .58) compared with the excess cold pattern group (1.16 ± 0.72); and (3) there was a higher mean score for nociceptive sensory descriptors in the excess cold pattern group (1.23 ± 0.45) compared with the excess heat pattern group (1.14 ± 0.62). The difference in the hot-burning mean score between the two TCM pattern groups was statistically significant (t [34] = 6.55, p < 0.0001).

CONCLUSION

Intriguing trends were observed in the pain scores for the two TCM pattern groups. The possibility that TCM pattern groups have different types of pain (neuropathic vs. nociceptive) deserves further research in larger samples. If these exploratory findings are confirmed, the characterization of TCM patterns could lead to new treatments for vulvodynia.

Patient-reported neuropathic pain in adolescent and young adult cancer patients

BACKGROUND

Neuropathic pain, a known complication of cancer and its treatments, negatively impacts quality of life. There are limited data using screening tools to aid in the diagnosis of neuropathic pain in cancer patients. Our primary objective was to determine the proportion of adolescent and young adult cancer patients reporting neuropathic pain on a patient-completed, neuropathic pain screening tool.

PROCEDURES

This prospective, cohort study enrolled patients 14-39 years of age who were receiving therapy for primary cancer diagnosis, cancer relapse, or had recently completed treatment. The painDETECT, a patient-completed, neuropathic pain screening tool used down to age 14, was administered a maximum of three times in on-therapy patients and once in off-therapy patients. Provider documentation of neuropathic pain at the corresponding visit was abstracted from the medical record.

RESULTS

Seventy-eight patients participated. Median (interquartile range) age at study enrollment was 18.1 (16-19.4) years and 47% were female. Cancer diagnoses included 41% leukemia, 26% solid tumor, 23% lymphoma, and 10% central nervous system tumor. The proportion of patients reporting neuropathic pain was 26% (95% confidence interval [CI] 16-40%) in on-therapy patients and 11% (95% CI 3-27%) in off-therapy patients. In patients reporting neuropathic pain, only 26% had a clinical diagnosis of neuropathic pain documented in the medical record at the corresponding visit.

CONCLUSIONS

Neuropathic pain occurs in one in four adolescents and young adults receiving cancer therapy. Use of screening tools may increase the detection of neuropathic pain in adolescents and young adults receiving cancer therapy and could ultimately improve pain treatment.

Non-pharmacological treatment for neuropathic pain in children with cancer

Neuropathic pain (NP) associated with childhood cancer is currently a difficult problem to control. It is treated with drugs that not only fail to provide the expected improvements, but which also have side effects. Therefore, the main aim of this pilot study is to assess whether non-pharmacological treatments, Graded Motor Imagery (GMI) and Neural Mobilization (NM), have a positive effect on this pain, thus improving the associated comorbid factors and, consequently, the quality of life of the children. In an n = 6, the results after 4 weeks of treatment show a 10-point improvement in the pain threshold and a 3.1-point improvement in the perception of pain.

Painful decisions for senior pets

Osteoarthritis and cancer are the inevitable consequences of aging and significantly contribute to the cause of death in cats and dogs. Managing the pain associated with these disease states is the veterinarian’s mandate. Many treatment modalities and agents are available for patient management; however, it is only with an understanding of disease neurobiology and a mechanism-based approach to problem diagnosis that the clinician can offer patients an optimal quality of life based on evidence-based best medicine. When treating pain, knowledge is still our best weapon.

Acute cavernous sinus syndrome from metastasis of lung cancer to sphenoid bone

Cavernous sinus syndrome is a rare entity in oncology reported only in occasional case reports. Optimal therapy is thus poorly defined with rapidly progressive disease dominating the picture. Management includes prompt diagnosis, attempts at stabilization of cranial nerve function, and aggressive control of central pain syndrome. Here, we report cavernous sinus syndrome secondary to the original squamous cell carcinoma of the lung. With common presenting causes of this syndrome being infection, thrombosis or tumor, it might seem that metastatic tumor would be expected in a patient with a cancer diagnosis. What was not so expected was the extremely rapid progression from mild headache and mild trigeminal neuralgia with negative-contrast head CT to a massive, destructive lesion involving several skull bones and skull base, only 3 weeks later. In addition, the patient was severely immunosuppressed at the completion of induction chemotherapy. Infectious processes, although unlikely, were considered, as aggressive cancer therapy (including high-dose steroids and radiation therapy) had no impact on this disease. Despite accurate localization, the aggressive nature of this disease with massive bone destruction and dural thickening limited any chance of a durable control. We discuss the process of evaluation, diagnosis and treatment of symptoms and the importance of a team approach to best palliate these unfortunate patients.

Modification of loco-regional microenvironment in brain tumors by spinal cord stimulation. Implications for radio-chemotherapy

The effectiveness of radiotherapy and chemotherapy in high grade gliomas (HGG) depends on tumor micro-environment. We summarize our experience of the influence of spinal cord stimulation (SCS) on this micro-environment. Patients with HGG (n = 26) were assessed pre- and post-SCS, using: (1) Doppler in middle cerebral arteries (MCA) and (2) in common carotid arteries (CCA); (3) tumor blood-flow using single photon emission computed tomography (SPECT); (4) tumor-pO(2) (mmHg) using polarographic probes (eight tumor areas from five patients); and (5) tumor glucose metabolism using (18)F-fluoro-2-deoxyglucose ((18)FDG) positron emission tomography ((18)FDG-PET). Pre-SCS: tumor blood-flow was lower (P < 0.001) than peri-tumor areas and healthy contra-lateral areas. Tumor-pO(2) was lower (P < 0.042) than healthy tissue. Tumor glucose metabolism was higher than peri-tumor areas (P = 0.017) and healthy contra-lateral areas (P = 0.048). Post-SCS: there were increases in: MCA blood-flow (P ≤ 0.002), CCA blood-flow (P ≤ 0.013), tumor blood-flow (P = 0.033), tumor glucose metabolism (P = 0.027) and tumor-pO(2) (P = 0.022). The percentage of hypoxic values decreased (P = 0.007). SCS can modify tumor micro-environment. The potential usefulness of SCS in improving the effectiveness of radio-chemotherapy in HGG needs to be evaluated.

[Neuropathic and tumour-induced headache: Therapeutic options]

Cancer pain in the field of otolaryngology can be effectively alleviated. Only very few questions regarding the patient's history of pain are required to understand the type of pain being dealt with and to be able to make the correct selection of analgetic agents. It is particularly important to treat tumor breakthrough pain appropriately, for which a sufficient number of therapeutic agents are available. The present article comments on the various possibilities of specific drugs and interventional therapeutic approaches, as well as their specific characteristics within the field of otolaryngology, supplemented with various tricks for their practical application. Using these basic rules, most problems can be identified and specific treatments optimized. The progression of cancer pain may show wide dynamic ranges, and the therapeutic approach should always be adjusted to the current situation. Palliative care of a cancer patient may be particularly challenging in that, not only the treatment of pain, but also the treatment of respiratory distress is of key importance.

Neuropathic pain features in patients with bone metastases referred for palliative radiotherapy

PURPOSE

To estimate the prevalence of pain with neuropathic features among patients with metastatic bone pain and to assess differences between patients with and without neuropathic features by pain severity, functional interference, and quality-of-life (QOL) measures.

PATIENTS AND METHODS

A prospective cross-sectional survey of consecutive patients with symptomatic bone metastases was conducted between December 2006 and March 2008 at a comprehensive cancer center. Patients completed the Brief Pain Inventory (BPI), the Self-Reported Leeds Assessment of Neuropathic Symptoms and Signs (S-LANSS), and the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire C30 (EORTC QLQ-C30). Statistical associations between pain with neuropathic features and other measures were explored.

RESULTS

Ninety-eight patients were enrolled. Seventeen percent of patients (95% CI, 10% to 24%) had positive S-LANSS scores suggesting pain with neuropathic features. Mean worst pain and mean interference scores were 7.2 (standard deviation [SD], 2.0) and 5.8 (SD, 2.5), respectively. EORTC QLQ-C30 global QOL, function, and symptom scores were 42 (SD, 24), 52 (SD, 20), and 46 (SD, 17), respectively. Patients with neuropathic features had a higher BPI worst pain score than patients without neuropathic features (8.3 v 7.0, respectively; P = .016). Corticosteroid use, oral morphine equivalent dosing, and site of bone pain were not associated with neuropathic features.

CONCLUSION

Some patients with bone metastases manifest bone pain with distinguishable neuropathic features, and these patients reported greater pain intensity. Additional work is required to validate the S-LANSS against clinical criteria for neuropathic pain in this context and to explore the unmet pain management needs in this population.

Patient-reported outcomes: descriptors of nociceptive and neuropathic pain and barriers to effective pain management in adult outpatients with sickle cell disease

Despite frequent episodes of severe recurrent pain in sickle cell disease (SCD), sensory pain in outpatient adults with SCD lacks sufficient characterization. Furthermore, pivotal barriers may interfere with these patients' adherence to prescribed analgesic therapies but have not been studied systematically. We describe sensory pain characteristics, barriers, and analgesic use reported by adults with SCD during routine clinic visits. Patients (N = 145; 67% female, 94% African American) completed measures on a pen-tablet computer. Patients reported an average of 3.6 +/- 2.3 pain sites; mean current pain intensity (3.3 +/- 3.2), least (3.0 +/- 2.7) and worst (4.9 +/- 3.5) pain intensity in 24 hours on a 0 to 10 scale, multiple neuropathic (4.5 +/- 3.4, 8.3% selected none) and nociceptive (6.8 +/- 4.0) pain descriptors, and continuous pain pattern (59%). Their mean pain barriers score was 2.2 +/- 0.9, and 33% were dissatisfied with their pain levels. Only 14% reported taking at least 1 adjuvant drug, 82% were taking nonopioids, 85% step 2 opioids, and 65% step 3 opioids. Patients reported using, on average, 4.9 +/- 2.7 analgesics. Their pain barriers scores were similar to or greater than people with cancer. Importantly, their pain may be both nociceptive and neuropathic, contrary to common expectations that SCD pain is only nociceptive. Few patients, however, took drugs effective for neuropathic pain.

Children with cancer and blood diseases experience positive physical and psychological effects from massage therapy

Background:

Previous research has shown positive effects from massage therapy (MT) for premature infants and for children with asthma, arthritis, and other illnesses. Although these effects have been demonstrated, MT research on children with cancer and blood disease is needed.

Purpose and Setting:

The present study, conducted at the Cancer Center, Shands Hospital, at the University of Florida, Gainesville, measured the physical and psychological effects of MT on pediatric oncology and hematology patients. The participants were 30 children with cancer or blood disease, ages 6 months to 17 years.

Research Design:

This randomized, non-blinded prospective study used measures of physical health and mental wellbeing that were completed before, during, and after four MT sessions were implemented. Descriptive statistics, one-way between-subjects analysis of variance, and an independent-samples t-test were used to analyze the data.

Intervention:

The treatment group received 20-minute sessions of Swedish MT once daily for approximately 4 days (inpatients), or once weekly for approximately 4 weeks (outpatients); the control group received no MT.

Results:

Between-groups analyses indicated significant psychological improvements for the MT group on state anxiety (F_1,58 = 16.79, p < 0.000), trait anxiety (F_1,58 = 3.95, p < 0.000), and emotional state (F_1,238 = 42.39, p < 0.001)]. Between-groups analyses indicated significant physical improvements for the MT group on muscle soreness (F_1,238 = 38.96, p < 0.001), discomfort (F_1,238 = 50.16, p < 0.001), respiratory rate (F_1,237 = 22.47, p < 0.000)], and overall progress (t₂₈ = 25.55, p < 0.000). No significant differences were found between groups on parent-completed ratings of their child’s physical or psychological health, pulse rate, or blood pressure.

Conclusions:

In children with cancer and blood diseases, MT can reduce psychological and physical distress and can have a positive effect on quality of life.

Development of a novel location-based assessment of sensory symptoms in cancer patients: preliminary reliability and validity assessment

We report on the development of a novel location-based assessment of sensory symptoms in cancer (L-BASIC) instrument, and its initial estimates of reliability and validity. L-BASIC is structured so that patients provide a numeric score and an adjectival description for any sensory symptom, including both pain and neuropathic sensations, present in each of the 10 predefined body areas. Ninety-seven patients completed the baseline questionnaire; 39 completed the questionnaire on two occasions. A mean of 3.5 body parts was scored per patient. On average, 2.7 (of 11) descriptor categories were used per body part. There was good internal consistency (Cronbach's alpha=0.74) for a four-item scale that combined location-specific metrics. Temporal stability was adequate (kappa>0.50 and r>0.60 for categorical and continuous variables, respectively) among patients without observed or reported subjective change in clinical status between L-BASIC administrations. We compared our four-item scale against scores obtained from validated pain and quality-of-life (QOL) scales, and as expected, correlations were higher for pain-related items than for QOL-related items. We detected differences in L-BASIC responses among patients with cancer-related head or neck pain, chemotherapy-related neuropathy and breast cancer-related lymphedema. We conclude that L-BASIC provides internally consistent and temporally stable responses, while acknowledging that further refinement and testing of this novel instrument are necessary. We anticipate that future versions of L-BASIC will provide reliable and valid syndrome-specific measurement of defined clinical pain and symptom constructs in the cancer population, which may be of particular value in assessing treatment response in patients with such multiple complaints.

Word Choices of Advanced Cancer Patients: Frequency of Nociceptive and Neuropathic Pain

The purpose of this study was to determine if nociceptive and/or neuropathic pain in advanced cancer patients could be identified by word selections made on the McGill Melzack Pain Questionnaire. Theoretical definitions for nociceptive and neuropathic pain provided a framework for categorizing the word descriptors in the McGill Melzack Pain Questionnaire's sensory and miscellaneous dimensions. A description study design was used to group word frequencies by primary site and pain type. The participants were 76 advanced cancer patients who received home-based hospice services. A wide range of word choices for lung cancer patients supported both nociceptive and neuropathic pain. Individuals with colon and liver cancer selected words that described 2 types of nociceptive (visceral, somatic) pain, while those with prostate cancer noted somatic pain. A set frequency was not reached by individuals with breast, pancreatic, gastric, and other advanced cancers. This study provided evidence that advanced cancer patients select words that describe nociceptive and neuropathic pain types.

Pharmacological evaluation of morphine and non-opioid analgesic adjuvants in a mouse model of skin cancer pain

Using a mouse model of advanced skin cancer which has mixed nociceptive-neuropathic pain, we evaluated the analgesic effects of morphine and analgesic adjuvants. Morphine hydrochloride (10--30 mg/kg, oral) and mexiletine hydrochloride (10--30 mg/kg, intraperitoneal) dose-dependently inhibited thermal hyperalgesia. Baclofen (10 mg/kg, subcutaneous) suppressed thermal hyperalgesia, without effects at lower doses of 1 and 5 mg/kg. Ketamine hydrochloride (50 mg/kg, oral) was without effect. Analgesic tolerance was observed after 6th administration of morphine, and it was not developed until at least 7th administration of mexiletine and baclofen. This mouse model of skin cancer may be useful for the pharmacological evaluation of the effects of opioids and analgesic adjuvants on mixed nociceptive-neuropathic pain of advanced cancer.

[Pain management, let us be simple but efficient]

The occurrence of pain during the course of bronchial carcinoma is nearly inescapable and often constitutes the main symptom for patients and those close to them. While pain control is held to be a priority of care in cancerology in the future, this goal is not always reached due to insufficient implementation of recommendations, however widely accessible. Our aim is to present the different aspects of pain treatment through the details of both pharmacological and nonpharmacological means.

Difficult Pain Syndromes

Cancer pain is prevalent in approximately two thirds of all cancer patients and can undermine the quality of life in this patient population. Uncontrolled pain can cause physical as well as psychological distress in cancer patients. As the disease progresses in cancer, pain and suffering increase. Knowledge about pain management is paramount in the comprehensive treatment of cancer patients. Difficult cancer pain syndromes may arise from interruption of bone, viscera, and neural structures by malignant spread of the disease. Familiarity with opioids, adjuvants, and procedures that can abate pain in cancer patients is discussed in a practical manner for clinical application in this text.

Management of Pediatric Patients With Complex Regional Pain Syndrome

This review summarizes current information about diagnosis and treatment of complex regional pain syndrome (CRPS) in children. Although it has been widely held that CRPS in children is intrinsically different from adults, there appear to be relatively few differences. However, there is a marked preponderance of lower extremity cases in children. Historically, psychological factors have been invoked to explain the genesis and persistence of CRPS in children, but the evidence is not compelling. Treatment outcome studies are limited but indicate that children generally respond to a primary focus on physical therapy. Multidisciplinary treatment reports are particularly encouraging. The general perception that children have a milder course may relate to the potentially greater willingness of children to actively participate in appropriately targeted treatment rather than to innate differences in the disease process itself. Recurrence rates appear higher than in adults, but response to reinitiation of treatment seems to proceed efficiently. Clinical judgment dictates the extent of medication or interventional therapy added to the treatment to facilitate rehabilitation. In many ways, the approach to the treatment of children mirrors that of adults, with perhaps greater restraint in the use of medications and invasive procedures. The rehabilitation of children with CRPS, like that of adults with CRPS, needs further rigorous investigation.

Use of antiepileptics and tricyclic antidepressants in cancer patients with neuropathic pain

Using a large US health insurance claims database, we identified all persons aged > or =18 years with > or =2 medical encounters with diagnoses of cancer and > or =2 medical encounters with diagnoses of painful neuropathies in calendar year (CY) 2000; persons with seizure disorders or depression were excluded. We then examined the use of antiepileptics (AEDs), tricyclic antidepressants (TCAs) and other pain-related pharmacotherapy among these selected persons, as proxied by pharmacy dispenses. A total of 956 persons were identified who met all entry criteria; 17% received AEDs in CY2000 and 14% received TCAs. Gabapentin was the most widely used AED (92% of all AED patients); amitriptyline was the most widely used TCA (79% of all TCA patients). Patients who received AEDs and/or TCAs were similar in age, gender and the presence of metastases to those who had not received these medications; they were more likely to have received other pain-related therapies, however, including short-acting opioids (73% vs. 53%; P < 0.01) and long-acting opioids (23% vs. 8%; P < 0.01). Use of AEDs and TCAs appears to be relatively low among cancer patients with painful neuropathies. Further research is needed to better understand reasons for this finding, as well as its potential implications for pain management in this patient population.

Chronic neuropathic pain. Mechanisms, diagnosis, and treatment

BACKGROUND

The management of chronic pain represents a significant public health issue in the United States. It is both costly to our health care system and devastating to the patient's quality of life. The need to improve pain outcomes is reflected by the congressional declaration of the present decade as the "Decade of Pain Control and Research," and the acknowledgment in January 2001 of pain as the "fifth vital sign" by the Joint Commission of Healthcare Organizations.

REVIEW SUMMARY

At present, therapeutic options are largely limited to drugs approved for other conditions, including anticonvulsants, antidepressants, antiarrhythmics, and opioids. However, treatment based on the underlying disease state (eg, postherpetic neuralgia, diabetic neuropathy) may be less than optimal, in that 2 patients with the same neuropathic pain syndrome may have different symptomatology and thus respond differently to the same treatment. Increases in our understanding of the function of the neurologic system over the last few years have led to new insights into the mechanisms underlying pain symptoms, especially chronic and neuropathic pain.

CONCLUSIONS

The rapidly evolving symptom- and mechanism-based approach to the treatment of neuropathic pain holds promise for improving the quality of life of our patients with neuropathic pain.

Parenteral Ketamine as an Analgesic Adjuvant for Severe Pain: Development and Retrospective Audit of a Protocol for a Palliative Care Unit

BACKGROUND

Ketamine is an effective analgesic agent for treating a variety of neuropathic and cancer pain syndromes. Recent studies indicate that ketamine may have a particular role in the management of patients with neuropathic and/or pain syndromes that are poorly responsive to opioids.

OBJECTIVE

To develop, implement, and subsequently assess a protocol designed to maximize the analgesic effect of ketamine while minimizing its side effects.

DESIGN

A retrospective chart audit of 16 patients who had used the ketamine protocol over a 12-month period. Criteria for assessing the effectiveness of ketamine were defined.

RESULTS

Ketamine was an effective, well-tolerated analgesic adjuvant for 11 of 16 patients with previously uncontrolled pain. Pain scores were reduced by at least 4 of 10 in 15 of the 16 patients. Median opioid dose reduction on starting ketamine was 25%.

CONCLUSION

The audit confirmed the safety and effectiveness of ketamine as an analgesic adjuvant for patients with severe pain. Baseline opioid dose reduction and prophylactic use of haloperidol or benzodiazepine were effective in minimizing psychotomimetic side effects.

Change of dorsal horn neurochemistry in a mouse model of neuropathic cancer pain

We investigated some neurochemical changes that take place in the spinal cord dorsal horn in a mouse model of neuropathic cancer pain. The model was produced by inoculation of Meth-A sarcoma cells to the vicinity of the sciatic nerve, which resulted in growth of a tumor mass embedding the nerve. Hind paw-lifting, a behavioral sign of spontaneous pain, was at maximum on Day 18, but decreased thereafter. The decrease was likely caused by progression of motor paralysis. On Day 18, thermal and mechanical pain thresholds of the affected paw were significantly increased. Histologically, the sciatic nerve presented damages to both unmyelinated and myelinated fibers on Day 18, which were more pronounced on Day 25. In the spinal cord, c-Fos-positive cells were significantly increased in the superficial and deep layers on Day 18. The number of c-Fos-positive cells in the superficial layer correlated with the duration of paw-lifting. The increase in c-Fos-positive cells was still present on Day 25 despite decreased paw-lifting. Substance P and calcitonin gene-related peptide were up-regulated on Day 18 but down-regulated on Day 25. A marked up-regulation of dynorphin A (DynA) was present on Day 18 and persisted through Day 25. Our model caused progressive damage to the sciatic nerve and presented spontaneous pain-behavior while the paw became hyposensitive to mechanical and thermal stimuli. Since the up-regulation of DynA in the dorsal horn persisted and paralleled the increase in c-Fos-positive cells, the release of DynA may be associated with spontaneous pain in our model.

Neuropathic pain in children with cancer

Different mechanisms of cancer pain may involve somatic, visceral, and neural tissues. Pain that involves the neural tissues is classified as neuropathic pain and is less responsive to analgesics than pain that involves somatic and visceral tissues. Because young children are unable to describe the quality of pain, presence of neuropathic pain with cancer may be unrecognized and undetected. The purpose of this article is to explain the nature of neuropathic pain, to review the literature related to children with cancer that suggests the presence of neuropathic pain, to outline assessment strategies that may lead to appropriate detection of neuropathic pain in children, and to discuss challenges in the management of neuropathic pain. Future research is needed to characterize the intensity, location, quality, and duration of neuropathic pain in children. In addition, research that would determine the efficacy of opioids, nonsteroidal anti-inflammatory drugs, and adjuvant analgesics (antidepressants, anticonvulsants) is needed to increase the nurses' ability to assess and manage neuropathic pain in children with cancer.

Adjuvant Analgesics in Cancer Pain Management

Adjuvant analgesics are defined as drugs with a primary indication other than pain that have analgesic properties in some painful conditions. The group includes numerous drugs in diverse classes. Although the widespread use of these drugs as first-line agents in chronic nonmalignant pain syndromes suggests that the term "adjuvant" is a misnomer, they usually are combined with a less-than-satisfactory opioid regimen when administered for cancer pain. Some adjuvant analgesics are useful in several painful conditions and are described as multipurpose adjuvant analgesics (antidepressants, corticosteroids, alpha(2)-adrenergic agonists, neuroleptics), whereas others are specific for neuropathic pain (anticonvulsants, local anesthetics, N-methyl-D-aspartate receptor antagonists), bone pain (calcitonin, bisphosphonates, radiopharmaceuticals), musculoskeletal pain (muscle relaxants), or pain from bowel obstruction (octreotide, anticholinergics). This article reviews the evidence supporting the use of each class of adjuvant analgesic for the treatment of pain in cancer patients and provides a comprehensive outline of dosing recommendations, side effects, and drug interactions.

Topical ketamine gel: possible role in treating neuropathic pain

Neuropathic pain is often resistant to opioids, so other medication classes, such as tricyclic antidepressants, anticonvulsants, and local anesthetics, are often used. Central sensitization, or pain 'wind-up', may perpetuate chronic neuropathic pain even when ongoing peripheral sensory input is absent. Wind-up is thought to cause allodynia, hyperalgesia, and hyperpathia. Receptors such as NMDA, AMPA, and M-glu have recently been identified for their role in central sensitization or pain 'wind-up'. Ketamine has been proposed recently for neuropathic pain secondary to its NMDA receptor activity. The current application as a topical gel stems from the theory that ketamine has peripheral action at both opioid and Na+-K+ channels. This case study involved 5 patients from 25 to 70 years old (3 RSD, 1 lumbar radiculopathy, 1 post-herpetic neuralgia). Dose used was determined by site and surface area of involvement and ranged from 0.093 mg/kg to 9.33 mg/kg. All five patients reported significant pain relief at initial application and wished to continue treatment. The average numerical analogue scale (NAS) score preapplication was 8.8. The average 15 minutes post application NAS was 1.6. Patients reported alterations in temperature sensation, feelings of relaxation and decreased tension in the area of application, and pain relief. Reduction in numerical pain scores postapplication of ketamine gel ranged from 53-100% using a 1-10 numerical pain intensity scale. No significant side effects were reported. Ketamine Gel may provide clinicians with a new option in the battle against chronic neuropathic pain. Until further information is available and larger trials can be conducted, we can only recommend this type of therapy for refractory cases in which all primary and secondary options have been exhausted.

Nociceptive response to innocuous mechanical stimulation is mediated via myelinated afferents and NK-1 receptor activation in a rat model of neuropathic pain

Peripheral nerve injury in humans can produce a persistent pain state characterized by spontaneous pain and painful responses to normally innocuous stimuli (allodynia). Here we attempt to identify some of the neurophysiological and neurochemical mechanisms underlying neuropathic pain using an animal model of peripheral neuropathy induced in male Sprague-Dawley rats by placing a 2-mm polyethylene cuff around the left sciatic nerve according to the method of Mosconi and Kruger. von Frey hair testing confirmed tactile allodynia in all cuff-implanted rats before electrophysiological testing. Rats were anesthetized and spinalized for extracellular recording from single spinal wide dynamic range neurons (L(3-4)). In neuropathic rats (days 11-14 and 42-52 after cuff implantation), ongoing discharge was greater and hind paw receptive field size was expanded compared to control rats. Activation of low-threshold sensory afferents by innocuous mechanical stimulation (0.2 N for 3 s) in the hind paw receptive field evoked the typical brief excitation in control rats. However, in neuropathic rats, innocuous stimulation also induced a nociceptive-like afterdischarge that persisted 2-3 min. This afterdischarge was never observed in control rats, and, in this model, is the distinguishing feature of the spinal neural correlate of tactile allodynia. Electrical stimulation of the sciatic nerve at 4 and at 20 Hz each produced an initial discharge that was identical in control and in neuropathic rats. This stimulation also produced an afterdischarge that was similar at the two frequencies in control rats. However, in neuropathic rats, the afterdischarge produced by 20-Hz stimulation was greater than that produced by 4-Hz stimulation. Given that acutely spinalized rats were studied, only peripheral and/or spinal mechanisms can account for the data obtained; as synaptic responses from C fibers begin to fail above approximately 5-Hz stimulation [Pain 46 (1991) 327], the afterdischarge in response to 20-Hz stimulation suggests a change mainly in myelinated afferents and a predominant role of these fibers in eliciting this afterdischarge. These data are consistent with the suggestion that peripheral neuropathy induces phenotypic changes predominantly in myelinated afferents, the sensory neurons that normally respond to mechanical stimulation. The NK-1 receptor antagonist, CP-99,994 (0.5 mg/kg, i.v.), depressed the innocuous pressure-evoked afterdischarge but not the brief initial discharge of wide dynamic range neurons, and decreased the elevated ongoing rate of discharge in neuropathic rats. These results support the concept that following peripheral neuropathy, myelinated afferents may now synthesize and release substance P. A result of this is that tonic release of substance P from the central terminals of these phenotypically altered neurons would lead to ongoing excitation of NK-1-expressing nociceptive spinal neurons. In addition, these spinal neurons would also exhibit exaggerated responses to innocuous pressure stimulation. The data in this study put forth a possible neurophysiological and neurochemical basis of neuropathic pain and identify substance P and the NK-1 receptor as potential neurochemical targets for its management.

Analysis and treatment of different types of neuropathic cancer pain

Neuropathic pain is a major problem in the treatment of cancer pain. We performed a retrospective analysis of 213 cancer patients with neuropathic pain treated by a pain service following the World Health Organization guidelines for relief of cancer pain. Of these, 79% presented with nerve compression pain, 16% with nerve injury pain, and 5% with sympathetically-maintained pain. Whereas nerve compression and nerve injury pain were caused most frequently by cancer growth, sympathetically-maintained pain was caused most frequently by cancer treatment. There were no significant differences in the use of analgesics, the mean pain intensity, or the efficacy of analgesic treatment among the three groups. Nerve injury pain and sympathetically-maintained pain were treated more frequently with adjuvant analgesics, especially antidepressants and anticonvulsants. The variety of different neuropathic pain syndromes should be separated in future studies of the efficacy of different treatment approaches.

Animal and cellular models of chronic pain

Chronic pain, especially neuropathic pain and cancer pain, is often not adequately treated by currently available analgesics. Animal models provide pivotal systems for preclinical study of pain. This article reviews some of the most widely used or promising new models for chronic pain. Partial spinal ligation, chronic constriction injury, and L5/L6 spinal nerve ligation represent three of the best characterized rodent models of peripheral neuropathy. Recently, several mouse and rat bone cancer pain models have been reported. Primary or permanent cultures of sensory neurons have been established to study the molecular mechanism of pain, especially for neurotransmitter release and signal transduction. The emerging gene microarray, genomics and proteomics methods may be applied to throughly characterize these cells. Each model is uniquely created with distinct mechanisms, it is therefore essential to report and interpret results in the context of a specific model.

Medication-focused approach to total pain: poor symptom control, polypharmacy, and adverse reactions

Neuropathic pain, known to have poor opioid response, can be difficult to control. Although several classes of adjuvant medications are believed to be of benefit in managing neuropathic pain, they have potential side effects that occasionally outweigh their benefits. The psychospiritual suffering of patients with advanced cancer may heighten the distress associated with physical symptoms. If undiagnosed, this may lead to increases in dose and the number of medications administered in the hope of better symptom control. This case report describes the successful interdisciplinary management of an advanced cancer patient whose multiple drug therapy had added to rather than alleviated his distress by causing more side effects than symptom relief.

Increased locoregional blood flow in brain tumors after cervical spinal cord stimulation

OBJECT

Patients with high-grade gliomas have poor prognoses following standard treatment. Generally, malignant brain tumors have a decreased blood flow that results in increased resistance to radiation and reduced delivery of chemotherapeutic agents and oxygen. The aim of the present study was to assess the effect of spinal cord stimulation (SCS) on locoregional blood flow in high-grade tumors in the brain.

METHODS

Fifteen patients (11 with Grade III and four with Grade IV brain tumors) had SCS devices inserted prior to scheduled radiotherapy. Both before and after SCS, the patients underwent the following procedures: 1) single-photon emission computerized tomography (SPECT) scanning; 2) middle cerebral artery (MCA) blood flow velocity measurements (centimeters/second) with the aid of transcranial Doppler (TCD) ultrasonography; and 3) common carotid artery (CCA) blood flow volume quantification (milliliters/minute) based on time-domain processing by using color Doppler ultrasonography. The indices demonstrated on SPECT scanning before SCS were significantly lower (p < 0.001) in tumor sites compared with those in peritumoral sites (32%) and healthy contralateral areas (41%). Poststimulation results revealed the following: 1) a mean increase of 15% in tumor blood flow in 75% of patients (p = 0.033), as demonstrated on SPECT scanning: 2) a mean increase of greater than 18% in systolic and diastolic blood flow velocities in both tumorous and healthy MCAs in all but one patient (p < 0.002), as exhibited on TCD ultrasonography; and 3) a mean increase of greater than 60% in blood flow volume in tumorous and healthy CCAs in all patients (p < 0.013), as revealed on color Doppler ultrasonography studies.

CONCLUSIONS

Preliminary data show that SCS can modify locoregional blood flow in high-grade malignant tumors in the brain, thus indicating that SCS could be used to improve blood flow, oxygenation, and drug delivery to such tumors and could be a useful adjuvant in chemoradiotherapy.

Rapid increase of morphine and benzodiazepine usage in the last three days of life in children with cancer is related to neuropathic pain

OBJECTIVE

To test the hypothesis that children with terminal cancer and neuropathic pain require rapid increases of opioids and benzodiazepines immediately before death, we compared drug usage in the last 72 hours of life in children with and without neuropathic pain.

PATIENTS AND METHODS

Through the use of retrospective case analysis, pediatric patients with terminal cancer were divided into two groups: one with and one without neuropathic pain. Opioid and benzodiazepine dosages were recorded during the last 3 days of life.

RESULTS

Eighteen patients were identified: 12 with neuropathic pain and 6 without neuropathic pain. In the neuropathic group, the average dose of morphine 72 hours before death was 231 mg/kg per day and increased to 380 mg/kg per day on the day of death (P =.009). The average benzodiazepine dosage 72 hours before death was 6.0 mg/kg per day and increased to 25.0 mg/kg per day on the day of death (P =.018). In the nonneuropathic pain group, the average dose of morphine and benzodiazepine 72 hours before death was 3.0 mg/kg per day and 0.08 mg/kg per day, respectively, and did not increase substantially on the day of death.

CONCLUSIONS

Dying children with cancer and neuropathic pain have higher baseline requirements of morphine and benzodiazepines and require rapid increases of both drugs in the last 72 hours of life than dying children without neuropathic pain.

A pilot study of the beneficial effects of amantadine in the treatment of painful diabetic peripheral neuropathy

BACKGROUND

Current symptomatic treatments for painful peripheral neuropathy in diabetes have variable efficacy in individual patients. Amongst other chemical transmitters involved in pain reception, the N-methyl-D-aspartate (NMDA) subtype of excitatory amino acid receptor is involved in nociception. Amantadine was recently shown to act as a non-competitive antagonist of NMDA and may be effective in the treatment of neuropathic pain in patients with cancer. We have looked at the benefit of amantadine infusion in diabetic patients with painful peripheral neuropathy.

METHODS

Seventeen patients with diabetes (nine men) completed this double-blind randomized crossover placebo-controlled trial of intravenous amantadine. The average age was 58.4 (sd 11) years, with duration of diabetes of 21.1 (8.7) years and duration of painful peripheral neuropathy symptoms of 29.1 (24) months. All analgesics except paracetamol were stopped for 4 weeks prior to the study. Infusions were carried out on a weekly basis with amantadine being administered intravenously as a single 200-mg infusion. The Neuropathy Symptom Score (NSS), together with visual analogue scales, were used to assess current pain intensity (VAS-P) pre-therapy and 1 week later VAS-P was repeated together with a visual analogue scale used to assess relief in pain (VAS-R) and the Physicians Global Evaluation (PGE) score used to assess response to therapy.

RESULTS

Pre-therapy, the NSS was 6.8 (6.3-7.4) at baseline, remaining unchanged at 6.6 (5.8-7.4) after placebo (P = 0.33), but fell to 4.6 (3.4-5.8) after amantadine (P = 0.003 vs. baseline and P = 0.02 vs. placebo). The baseline perception of pain was scored as 7.8 cm (7.3-8.3), with no difference following placebo, at 8.2 cm (7.7-8.6) (P = 0.34), but following amantadine it fell to 6.2 cm (4.9-7.8) (P = 0.01 compared with pre-therapy, P = 0.003 compared with placebo). The perception of relief from pain following placebo was only 0.2 (-0.2 to +0.6) but following amantadine was 10-fold better at 1.9 (0.8-3.1) (P = 0.016). The PGE assessment of pain relief was -0.3 (-0.5 to 0) for placebo and following amantadine was 0.8 (0.1-1.5) (P = 0.006).

CONCLUSIONS

Our study has shown that intravenous amantadine is beneficial in reducing the pain of painful peripheral neuropathy, with an effect sustained for at least 1 week after an infusion.

A mouse model of neuropathic cancer pain

We developed a mouse model of neuropathic cancer pain by inoculating Meth A sarcoma cells to the immediate proximity of the sciatic nerve in BALB/c mice. The tumor grows predictably with time and gradually compresses the nerve, thereby causing nerve injury. Time courses of thermal hyperalgesia and mechanical sensitivity to von Frey hairs were determined and signs of spontaneous pain were evaluated. We compared this model with the chronic constriction injury (CCI) model, which is a neuropathic pain model widely utilized in the rat. Furthermore, to characterize the difference in nerve injury between the two models, we performed histological examination of the nerve of the two models by light and electron microscopy. Progressive compression of the sciatic nerve by growth of a tumor mass resulted in a gradual development of thermal hyperalgesia and mechanical allodynia in the ipsilateral hind paw. Signs of spontaneous pain, such as lifting of the paw, were also observed. However, further growth of the tumor reversed the mechanical hypersensitivity and produced mechanical hyposensitivity, while thermal hyperalgesia and signs of spontaneous pain still persisted. Histologically, gradual compression by the tumor resulted in a progressive damage to both myelinated and unmyelinated fibers. However, the severity of damage to the myelinated fibers was considerably less compared to that of the CCI mice. In the CCI mice, severe damage to myelinated fibers, especially large fibers, was observed and unmyelinated fibers were damaged to a lesser degree. These results suggest that gradual compression of a nerve by a malignant tumor results in nerve damage with a profile considerably different from that of chronic constriction injury produced by loose ligation of the nerve. Our new tumor model may be useful in studies of neuropathic cancer pain due to nerve compression by malignant tumors.

Quality improvement of painful peripheral neuropathy

OBJECTIVES

To use quality improvement methodology to improve the assessment and treatment of neuropathic pain caused by chemotherapy-related nerve injury.

DATA SOURCES

Review and research articles, assessment scales, and textbooks.

CONCLUSIONS

Assessment and treatment algorithms improved peripheral neuropathy-related pain scores. Patient satisfaction with medication effectiveness decreased over time. Medication costs increased, but specialist-referral costs decreased.

IMPLICATIONS FOR NURSING PRACTICE

Nurse-led quality improvement work can lead to positive changes in clinical practice.

Nociceptive and neuropathic pain in patients with lung cancer: a comparison of pain quality descriptors

Predictive validity of each word from the McGill Pain Questionnaire (MPQ) has not been investigated in relation to pain etiology. The purpose of this study was to explore differences in the words used to describe nociceptive and neuropathic pain. Patients with lung cancer (N = 123) selected words from the 78 MPQ pain quality descriptors and indicated the corresponding pain site for each word. Using only the MPQ pain location, and the cancer and treatment data abstracted from medical records, each pain site was classified as nociceptive or neuropathic (etiology). Pain etiology and quality descriptors were tested for proportional differences with sensitivity, specificity, and predictive value calculated for statistically significant descriptors. Of the 457 pain sites, 343 were classified as nociceptive (75%), 114 as neuropathic (25%). Lacerating, stinging, heavy, and suffocating were selected for a significantly larger proportion of nociceptive sites whereas throbbing, aching, numb, tender, punishing, pulling, tugging, pricking, penetrating, punishing, miserable, and nagging were selected for a larger proportion of neuropathic sites. Ten words correctly predicted 78% of the sites with 81% sensitivity to nociceptive pain and 59% sensitivity to neuropathic pain. Interestingly, several pain quality descriptors (burning, shooting, flashing, tingling, itching, and cold) previously associated with neuropathic pain did not distinguish between neuropathic and nociceptive pain. Infrequent selection of many MPQ words and lack of neurological exam data in the medical records are possible explanations for inconsistency with previous literature. Prospective studies are needed to validate pain quality descriptors for nociceptive and neuropathic types of lung cancer pain.