Predictors of severe pain in a cohort of 5271 individuals with self-reported neuropathic pain

Patient and clinician beliefs about potential barriers to treatment of neuropathic pain for adolescents with sickle cell disease

Pain is the hallmark symptom causing morbidity for people with sickle cell disease (SCD) and may present as nociceptive, neuropathic, or mixed type pain. Neuropathic pain (NP) is underrecognized and undertreated in patients with SCD and is associated with decreased patient-reported quality of life. Surveys were completed by clinicians caring for adolescents with SCD in the outpatient setting. SCD patients ages 1418 at increased risk of NP completed a patient-facing survey at a scheduled clinic visit. Ninety-four percent of responding clinicians agreed that NP significantly contributes to reported pain in SCD. Clinicians believed that NP medications are effective for reducing chronic pain (62%) and decreasing opioid utilization (44%). Clinician-identified barriers to prescribing NP medications included concerns about medication adherence (82%), lack of pediatric guidelines for NP medications (70%), and perceived patient concern about side effects (65%). More than 1/3 (35%) of clinicians reported that they were not comfortable managing NP medications. Clinician-identified barriers to referral to a pain management specialist included scheduling concerns (88%) and perceived patient/family lack of interest (77%). Most patients expressed willingness to take a medication for NP (78%), see a pain management specialist (84%), or learn more about nonpharmacologic interventions (72%), although most (51%) also reported some concerns about taking a medication for NP, citing insufficient knowledge (34%), and potential for side effects (32%). A minority of respondents (15%) worried about referral to a pain management specialist. Clinician and patient perspectives provide insights that may guide education efforts or other interventions to improve treatment of SCD-related NP.

Pain in sickle cell disease: current and potential translational therapies

Pain is a major comorbidity of sickle cell disease (SCD). Patients with SCD may suffer from both acute and chronic pain. Acute pain is caused by recurrent and unpredictable episodes of vaso-occlusive crises (VOC), whereas the exact etiology of chronic pain is still unknown. Opioids are the mainstay for pain treatment, but the opioid epidemic has significantly altered access to prescription opioids and has brought concerns over their long-term use into the forefront, which have negatively impacted the treatment of sickle pain. Opioids remain potent analgesics but growing opioid-phobia has led to the realization of an unmet need to develop nonopioid therapies that can provide relief for severe sickle pain. This realization has contributed to the approval of 3 different drugs by the Food and Drug Administration (FDA) for the treatment of SCD, particularly to reduce VOC and/or have an impact on the pathobiology of SCD. In this review, we outline the challenges and need for validation of side-effects of opioids and provide an update on the development of mechanism-based translational therapies, specifically targeting pain in SCD.

Predictors of pain in general ageing populations: results from a multi-country analysis based on ATHLOS harmonized database

BACKGROUND

Pain is a common symptom, often associated with neurological and musculoskeletal conditions, and experienced especially by females and by older people, and with increasing trends in general populations. Different risk factors for pain have been identified, but generally from studies with limited samples and a limited number of candidate predictors. The aim of this study is to evaluate the predictors of pain from a large set of variables and respondents.

METHODS

We used part of the harmonized dataset of ATHLOS project, selecting studies and waves with a longitudinal course, and in which pain was absent at baseline and with no missing at follow-up. Predictors were selected based on missing distribution and univariable association with pain, and were selected from the following domains: Socio-demographic and economic characteristics, Lifestyle and health behaviours, Health status and functional limitations, Diseases, Physical measures, Cognition, personality and other psychological measures, and Social environment. Hierarchical logistic regression models were then applied to identify significant predictors.

RESULTS

A total of 13,545 subjects were included of whom 5348 (39.5%) developed pain between baseline and the average 5.2 years' follow-up. Baseline risk factors for pain were female gender (OR 1.34), engaging in vigorous exercise (OR 2.51), being obese (OR 1.36) and suffering from the loss of a close person (OR 1.88) whereas follow-up risk factors were low energy levels/fatigue (1.93), difficulties with walking (1.69), self-rated health referred as poor (OR 2.20) or average to moderate (OR 1.57) and presence of sleep problems (1.80).

CONCLUSIONS

Our results showed that 39.5% of respondents developed pain over a five-year follow-up period, that there are proximal and distal risk factors for pain, and that part of them are directly modifiable. Actions aimed at improving sleep, reducing weight among obese people and treating fatigue would positively impact on pain onset, and avoiding vigorous exercise should be advised to people aged 60 or over, in particular if female or obese.

Targeting Peripherally Restricted Cannabinoid Receptor 1, Cannabinoid Receptor 2, and Endocannabinoid-Degrading Enzymes for the Treatment of Neuropathic Pain Including Neuropathic Orofacial Pain

Neuropathic pain conditions including neuropathic orofacial pain (NOP) are difficult to treat. Contemporary therapeutic agents for neuropathic pain are often ineffective in relieving pain and are associated with various adverse effects. Finding new options for treating neuropathic pain is a major priority in pain-related research. Cannabinoid-based therapeutic strategies have emerged as promising new options. Cannabinoids mainly act on cannabinoid 1 (CB1) and 2 (CB2) receptors, and the former is widely distributed in the brain. The therapeutic significance of cannabinoids is masked by their adverse effects including sedation, motor impairment, addiction and cognitive impairment, which are thought to be mediated by CB1 receptors in the brain. Alternative approaches have been developed to overcome this problem by selectively targeting CB2 receptors, peripherally restricted CB1 receptors and endocannabinoids that may be locally synthesized on demand at sites where their actions are pertinent. Many preclinical studies have reported that these strategies are effective for treating neuropathic pain and produce no or minimal side effects. Recently, we observed that inhibition of degradation of a major endocannabinoid, 2-arachydonoylglycerol, can attenuate NOP following trigeminal nerve injury in mice. This review will discuss the above-mentioned alternative approaches that show potential for treating neuropathic pain including NOP.

Significant Quantitative Differences in Orexin Neuronal Activation After Pain Assessments in an Animal Model of Sickle Cell Disease

Sickle cell disease is a hemoglobinopathy that causes sickling of red blood cells, resulting in vessel blockage, stroke, anemia, inflammation, and extreme pain. The development and treatment of pain, in particular, neuropathic pain in sickle cell disease patients is poorly understood and impedes our progress toward the development of novel therapies to treat pain associated with sickle cell disease. The orexin/hypocretin system offers a novel approach to treat chronic pain and hyperalgesia. These neuropeptides are synthesized in three regions: perifornical area (PFA), lateral hypothalamus (LH), and dorsomedial hypothalamus (DMH). Data suggest that orexin-A neuropeptide has an analgesic effect on inflammatory pain and may affect mechanisms underlying the maintenance of neuropathic pain. The purpose of this study was to determine whether there are neuronal activation differences in the orexin system as a result of neuropathic pain testing in a mouse model of sickle cell disease. Female transgenic sickle mice that express exclusively (99%) human sickle hemoglobin (HbSS-BERK) and age-/gender-matched controls (HbAA-BERK mice; n = 10/group, 20-30 g) expressing normal human hemoglobin A were habituated to each test protocol and environment before collecting baseline measurements and testing. Four measures were used to assess pain-related behaviors: thermal/heat hyperalgesia, cold hyperalgesia, mechanical hyperalgesia, and deep-tissue hyperalgesia. Hypothalamic brain sections from HbAA-BERK and HbSS-BERK mice were processed to visualize orexin and c-Fos immunoreactivity and quantified. The percentage of double labeled neurons in the PFA was significantly higher than the percentage of double labeled neurons in the LH orexin field of HbAA-BERK mice (* p < 0.05). The percentages of double labeled neurons in PFA and DMH orexin fields are significantly higher than those neurons in the LH of HbSS-BERK mice (* p < 0.05). These data suggest that DMH orexin neurons were preferentially recruited during neuropathic pain testing and a more diverse distribution of orexin neurons may be required to produce analgesia in response to pain in the HbSS-BERK mice. Identifying specific orexin neuronal populations that are integral in neuropathic pain processing will allow us to elucidate mechanisms that provide a more selective, targeted approach in treating of neuropathic pain in sickle cell disease.

Pain descriptors of taxane acute pain syndrome (TAPS) in breast cancer patients-a prospective clinical study

BACKGROUND

Taxane acute pain syndrome (TAPS) is a clinically significant side-effect of taxane chemotherapy, often described as arthralgia and myalgia that occurs 2-3 days after infusion. The aim of this study was to assess pain descriptors used by patients during their experience of TAPS.

METHODS

A clinical prospective cohort study was conducted on breast cancer patients who had not received prior chemotherapy and were asked to complete diaries on three consecutive docetaxel treatment cycles on days 1-7, 14, and 21 (acute phase). Questionnaires to assess pain severity, descriptors of pain, and the interference in activities due to pain were adapted from the Brief Pain Inventory and the McGill Pain Questionnaire. Telephone questionnaire follow-up was done at 1, 3, 6, 9, and 12 months following docetaxel (delayed phase).

RESULTS

The most commonly used descriptor for acute and chronic pain was "aching" (90-96%). However, in the delayed phase of the study, "burning" (32-50%), "radiating" (39-48%), and "sharp" (40-69%) were used more often. In both acute and chronic pain phases, most patients experienced moderate/severe pain regardless of the location. Pain in cycle 1 was predictive of pain in subsequent taxane cycles (p < 0.0001). Pain in cycle 3 was predictive of chronic pain (p < 0.002).

CONCLUSIONS

The descriptors used by patients experiencing chemotherapy-induced pain (ChIP) may be reflective of the underlying mechanisms. It is suspected that TAPS initiates as an acute inflammatory pain, which over time develops into neuropathic pain, known as chemotherapy-induced peripheral neuropathy (CIPN). However, the subjective pain experience varies from patient to patient.

Efficacy of 50 mg pregabalin for prevention of postoperative neuropathic pain after video-assisted thoracoscopic surgery and thoracotomy: a 3-month prospective randomized controlled trial

Background

This study analyzed the preventive effect of 50 mg/day pregabalin on postoperative neuropathic pain, and any additional benefits related to sleep and respiratory function.

Methods

This prospective randomized controlled study included lung resection patients 20-89 years of age. Patients were randomly assigned to the treatment (pregabalin; initial dose, 50 mg/day) or control (non-steroidal anti-inflammatory drugs) group. Pregabalin patients received non-steroidal anti-inflammatory drugs and pregabalin (25 mg, twice daily) from the second postoperative day. Pain scores, neuropathic pain, analgesic use, respiratory function, and insomnia scale scores for 3 months after surgery were evaluated.

Results

This study included 46 patients who received pregabalin and 46 control patients. Pregabalin patients had significantly less postoperative neuropathic pain than control patients (19.6% vs. 41.3%; P=0.0404), and their duration of neuropathic pain was significantly shorter (30 vs. 90 days; P=0.024). The onset of postoperative neuropathic pain, insomnia scale scores, and respiratory function were similar between groups. No pregabalin-related adverse events were reported.

Conclusions

Pregabalin (50 mg/day) had a significant preventive effect on postoperative neuropathic pain after thoracic surgery, without side effects. Early postoperative administration of pregabalin would help prevent neuropathic pain and provide better pain control after thoracic surgery.

Risk factors of neuropathic pain after thoracic surgery

Background

This study aimed to clarify the incidence and risk factors of neuropathic pain after thoracic surgery, focusing especially on patients who underwent complete video-assisted thoracoscopic surgery (VATS).

Methods

We retrospectively identified 185 patients who underwent thoracic surgery at our hospital over a 2-year period. Logistic regression analysis was used to analyze the association of various factors with postoperative neuropathic pain.

Results

Forty-eight (25.9%) patients developed postoperative neuropathic pain, and 9 (18.8%) of these patients reported persistent pain 1 year postoperatively. The median interval from surgical treatment to the onset of neuropathic pain was 7 days, and the duration was 50 days. Multivariate logistic regression analysis revealed a significant positive correlation between postoperative neuropathic pain and preoperative use of hypnotic medication [odds ratio (OR), 5.45; 95% confidence interval (CI); 2.52-12.17] and duration of surgery ≥2.5 hours (OR, 2.72; 95% CI, 1.27-6.09), and a significant negative association with the complete VATS approach (OR, 0.18; 95% CI, 0.073-0.42).

Conclusions

Preoperative use of hypnotic medication, the thoracotomy approach, and duration of surgery ≥2.5 hours are associated with increased risk of neuropathic pain after thoracic surgery. The complete VATS approach could decrease the incidence of postoperative neuropathic pain, regardless of the duration of surgery.

Sensory Symptom Profiles of Patients With Neuropathic Pain After Spinal Cord Injury

AIM

Individuals experiencing neuropathic pain (NP) after spinal cord injury (SCI) present with a variety of pain descriptors in different combinations and at different intensities. These sensory features form distinct patterns, known as sensory symptom profiles.

METHODS

In the present cross-sectional study, we have used a multivariate statistical method (multiple correspondence analysis) to categorize the sensory symptom profiles of a cohort of 338 patients with at-level or below-level NP after SCI. We also investigated possible associations between positive neuropathic symptoms and features of the neurological lesion.

RESULTS

The majority of participants had a combination of pain descriptors, with 59% presenting with 3 or 4 pain subtypes. No significant associations were found between specific pain profiles and etiology or clinical degree of the neurological lesion. Furthermore, similar symptom profiles were seen in patients with at-level and below-level NP. The most frequent pattern observed in patients with cervical SCI consisted predominantly of electric shocks and tingling, without burning, pressure pain, or allodynia.

CONCLUSIONS

Classification of SCI-NP patients into the 5 groups identified in the present study based on their distinct sensory symptom profiles may allow identification of those most likely to respond to a specific analgesic approach.

Anticonvulsants or Antidepressants in Combination Pharmacotherapy for Treatment of Neuropathic Pain in Cancer Patients: A Systematic Review and Meta-analysis

OBJECTIVE

To investigate the efficacy of anticonvulsants or antidepressants in combination pharmacotherapy for treatment of neuropathic pain in cancer patients.

MATERIALS AND METHODS

We systematically searched the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, and the metaRegister of Controlled Trials for randomized controlled trials that compared anticonvulsants or antidepressants in combination pharmacotherapy (experimental group) with treatments without anticonvulsants or antidepressants (control group) for neuropathic pain in cancer patients. Risk of bias was evaluated in accordance with the Cochrane Handbook for Systematic Reviews of Interventions. The primary outcome was a mean difference (MD) in change in global pain analyzed by a random-effects model.

RESULTS

Eight trials met the inclusion criteria with a total of 1359 participants of whom 698 received an experimental intervention. The MD in change in global pain suggested a favorable association with anticonvulsants or antidepressants in combination pharmacotherapy compared with control groups (MD, -0.41; 95% confidence interval, -0.70 to -0.12) with no heterogeneity across trials (I=0%). The MD in change estimated in all sensitivity analyses ranged from -0.36 to -0.47, suggesting that these effects were consistent across different study designs and statistical assumptions.

CONCLUSIONS

Anticonvulsants or antidepressants in combination pharmacotherapy reduce neuropathic pain in cancer patients compared with treatments without anticonvulsants or antidepressants. Limited evidence precludes a recommendation on specific adjuvants in combination pharmacotherapy.

Sex differences in a Murine Model of Complex Regional Pain Syndrome

Complex Regional Pain Syndrome (CRPS) is a major cause of chronic pain after surgery or trauma to the limbs. Despite evidence showing that the prevalence and severity of many forms of chronic pain, including CRPS, differ between males and females, laboratory studies on sex-related differences in animal models of CRPS are not available, and the impact of sex on the transition from acute to chronic CRPS pain and disability are unexplored. Here we make use of a tibia fracture/cast mouse model that recapitulates the nociceptive, functional, vascular, trophic, inflammatory and immune aspects of CRPS. Our aim is to describe the chronic time course of nociceptive, motor and memory changes associated with fracture/cast in male and female mice, in addition to exploring their underlying spinal mechanisms. Our behavioral data shows that, compared to males, female mice display lower nociceptive thresholds following fracture in the absence of any differences in ongoing or spontaneous pain. Furthermore, female mice show exaggerated signs of motor dysfunction, deficits in fear memory, and latent sensitization that manifests long after the normalization of nociceptive thresholds. Our biochemical data show differences in the spinal cord levels of the glutamate receptor NR2b, suggesting sex differences in mechanisms of central sensitization that could account for differences in duration and severity of CRPS symptoms between the two groups.

The use of neuropathic pain drugs in children with sickle cell disease is associated with older age, female sex, and longer length of hospital stay

Although neuropathic pain is increasingly recognized in sickle cell disease (SCD), it is unknown how neuropathic pain drugs are used in children with SCD. Thus, we investigated use of these drugs and hypothesized older age and female sex are associated with increased neuropathic drug use and the use of these drugs is associated with longer length of stay. We analyzed the Pediatric Health Information System (2004 to 2009) including all inpatient visits aged 0 to 18 years with any SCD-related (all genotypes) discharge diagnosis. To limit confounding we excluded psychiatric and seizure visits. Antiepileptics, tricyclic antidepressants, and selective serotonin reuptake inhibitors were drugs of interest. Generalized Estimating Equations determined the impact of age and sex on neuropathic drug use and the impact of neuropathic drug use on length of stay. We analyzed 53,557 visits; 2.9% received≥1 neuropathic drugs. The odds of receiving a neuropathic drug increased significantly with age (reference group, 0 to 4 y: 5 to 10, odds ratio [OR], 5.7; 11 to 14: OR, 12.5; 15 to 18: OR, 22.8; all P<0.0001] and female sex (OR, 1.5; P=0.001). Neuropathic drug use was associated with longer length of stay (risk ratio, 8.3; P<0.0001). Neuropathic drug use in children with SCD was associated with older age, female sex, and longer length of stay.

Measurement properties of painDETECT by average pain severity

Background

Since the burden of neuropathic pain (NeP) increases with pain severity, it is important to characterize and quantify pain severity when identifying NeP patients. This study evaluated whether painDETECT, a screening questionnaire to identify patients with NeP, can distinguish pain severity.

Materials and methods

Subjects (n=614, 55.4% male, 71.8% white, mean age 55.5 years) with confirmed NeP were identified during office visits to US community-based physicians. The Brief Pain Inventory – Short Form stratified subjects by mild (score 0–3, n=110), moderate (score 4–6, n=297), and severe (score 7–10, n=207) average pain. Scores on the nine-item painDETECT (seven pain-symptom items, one pain-course item, one pain-irradiation item) range from −1 to 38 (worst NeP); the seven-item painDETECT scores (only pain symptoms) range from 0 to 35. The ability of painDETECT to discriminate average pain-severity levels, based on the average pain item from the Brief Pain Inventory – Short Form (0–10 scale), was evaluated using analysis of variance or covariance models to obtain unadjusted and adjusted (age, sex, race, ethnicity, time since NeP diagnosis, number of comorbidities) mean painDETECT scores. Cumulative distribution functions on painDETECT scores by average pain severity were compared (Kolmogorov–Smirnov test). Cronbach’s alpha assessed internal consistency reliability.

Results

Unadjusted mean scores were 15.2 for mild, 19.8 for moderate, and 24.0 for severe pain for the nine items, and 14.3, 18.6, and 22.7, respectively, for the seven items. Adjusted nine-item mean scores for mild, moderate, and severe pain were 17.3, 21.3, and 25.3, respectively; adjusted seven-item mean scores were 16.4, 20.1, and 24.0, respectively. All pair-wise comparisons of scores between pain-severity groups showed sizable and statistically significant differences (P<0.0001). Cumulative distribution functions showed distinct separation between severity (P<0.0001). Cronbach’s alphas were 0.76 and 0.80 for the nine- and seven-item scales, respectively.

Conclusion

This study provides strong psychometric evidence on the validity and reliability of painDETECT for distinguishing average pain severity in patients with NeP.

Neuropathic pain in patients with sickle cell disease

BACKGROUND

Despite the suggestion of a neuropathic component to sickle cell disease (SCD) pain, there are minimal data on the systematic assessment of neuropathic pain in patients with SCD. Neuropathic pain is defined as pain primarily initiated by dysfunction of the peripheral or central nervous system.

PROCEDURE

In a cross-sectional study, we used the painDETECT questionnaire, a one-page validated neuropathic pain screening tool, to determine the presence of neuropathic pain in patients with SCD and to evaluate the relationship between neuropathic pain, age, and gender. We hypothesized that 20% of patients with SCD will experience neuropathic pain and that neuropathic pain will be associated with older age and female gender. The completed painDETECT questionnaire yields a total score between 0 and 38 (≥ 19 = definite neuropathic pain, 13-18 = probable neuropathic pain, ≤ 12 = no neuropathic pain). Scores ≥ 13 were designated as having evidence of neuropathic pain.

RESULTS

A total of 56 patients participated. Median age was 20.3 years and 77% were female. We found 37% of patients had evidence of neuropathic pain. Age was positively correlated with total score (r = 0.43; P = 0.001) suggesting older patients experience more neuropathic pain. Females had higher mean total scores (13 vs. 8.4; P = 0.04). Significantly more patients with neuropathic pain were taking hydroxyurea (90% vs. 59%; P = 0.015). Despite 37% of patients experiencing neuropathic pain, only 5% were taking a neuropathic pain drug.

CONCLUSIONS

Neuropathic pain exists in SCD. Valid screening tools can identify patients that would benefit from existing and future neuropathic pain therapies and could determine the impact of these therapies.