Psychological Characteristics and Pain Frequency Are Associated With Experimental Pain Sensitivity in Pediatric Patients With Sickle Cell Disease

Pain sensitisation in patients with sickle cell disease: A preliminary study

BACKGROUND

Responses to experimental pain have suggested central and peripheral sensitisation in adult patients with sickle cell disease (SCD). Recent studies have proposed an algometry-derived dynamic measure of pain sensitisation, slowly repeated evoked pain (SREP), which is useful in the discrimination of painful conditions related to central sensitisation. Pain and fatigue are two symptoms that affect the general functioning of patients with SCD most significantly, however, research about experimental dynamic pain measures and their relation to the main symptoms of SCD (pain and fatigue) is still scarce.

OBJECTIVE

This preliminary study aimed to test the utility of the SREP protocol for detecting pain sensitisation in patients with SCD, and to evaluate the associations of pain sensitisation, pain threshold, and pain tolerance with the main clinical symptoms of SCD, pain and fatigue.

METHODS

Twenty-two female outpatients with SCD and 20 healthy women participated. Pain threshold, pain tolerance, and pain sensitisation were assessed by algometry in the fingernail. Clinical pain, fatigue, anxiety, depression and pain catastrophizing were evaluated.

RESULTS

No group differences were found in pain threshold and tolerance. However, using the SREP protocol, pain sensitisation was greater in patients than in healthy participants, even after controlling for psychological variables and body mass index. Pain threshold and tolerance were inversely associated with fatigue levels in the SCD group, with pain tolerance being the main predictor.

CONCLUSIONS

Pain threshold and tolerance did not discriminate between patients and healthy individuals, but were useful for predicting fatigue severity in SCD. The SREP protocol provides a useful dynamic measure of pain for the discrimination and detection of enhanced pain sensitisation in patients with SCD, which could contribute to more personalised pain evaluations and treatment for these patients.

Weak Relationships Between Psychological Factors and Experimental Pain Outcomes in Pain-Free Individuals: An Aggregate Analysis of 8 Studies

Although psychological factors such as anxiety, depression, and pain catastrophizing are known to influence pain outcomes in chronic pain populations, there are mixed results regarding whether they influence experimental pain outcomes in pain-free individuals. The objectives of this study were to determine the associations between psychological factors and experimental pain outcomes in pain-free adolescents and adults. Relationships between anxiety, depression, and pain catastrophizing and experimental pain outcomes across 8 different studies (total N = 595) were examined in different populations of pain-free adult and adolescent participants. Analyses were conducted with and without controlling for sex, age, and race. Studies were analyzed separately and as part of an aggregate analysis. Individual study analyses resulted in 136 regression models. Of these, only 8 models revealed a significant association between psychological factors and pain outcomes. The significant results were small and likely due to Type 1 error. Controlling for demographic factors had minimal effect on the results. The aggregate analyses revealed weak relationships between anxiety and pressure pain threshold (Fisher's z = -.10 [-.19, -.01]), anxiety and cold pain intensity ratings (Fisher's z = .18 [.04, .32]), and pain catastrophizing and pressure pain threshold (Fisher's z = -.14 [-.26, -.02]). Sample size calculations based on the aggregate analyses indicated that several hundred participants would be required to detect true relationships between these psychological factors and pain measures. The overall negative findings suggest that in pain-free individuals, anxiety, depression, and pain catastrophizing are not meaningfully related to experimental pain outcomes. PERSPECTIVE: Psychological variables have been shown to predict pain outcomes in chronic pain populations but these relationships may not generalize to pain-free populations. An analysis of 595 pain-free individuals across 8 studies in our lab revealed that anxiety, depression, and pain catastrophizing were not meaningfully related to experimental pain outcomes.

Altered pain processing and sensitization in sickle cell disease: a scoping review of quantitative sensory testing findings

OBJECTIVES

Over 50% of adults living with sickle cell disease (SCD) have chronic pain, but the underlying mechanisms of chronic pain in this population remain unclear. Quantitative sensory testing is an important measurement tool for understanding pain and sensory processing. This scoping review summarizes quantitative sensory testing methodologies used in sickle cell studies and the evidence for central sensitization in this population.

METHODS

We conducted a systematic search of PubMed, Embase, and CINAHL to identify studies using quantitative sensory testing in individuals living with sickle cell disease. Search strategies were based on variations of the terms "sickle cell disease," and "quantitative sensory testing." Eligible studies were observational or experimental studies in human participants living with SCD that reported findings and detailed methodology for at least 1 quantitative sensory testing modality.

RESULTS

Our search yielded a total of 274 records; 27 of which are included in this scoping review. Of the 27 studies, 17 were original studies (with combined total of 516 adult and 298 pediatric participants), and 10 were secondary or subgroup analyses of these prior studies. Significant variation existed in quantitative sensory testing methodologies across studies, including testing locations, type and intensity of stimuli, and interpretation of findings. Of the identified studies, 22% (2/9 studies) reported sensory abnormalities in mechanical sensitivity and thresholds, 22% (2/9 studies) reported abnormal pressure pain thresholds, 46% (6/13 studies) reported sensory abnormalities in thermal pain thresholds and tolerance (cold and warm), and 50% (2/4 studies) reported abnormalities in temporal summation.

CONCLUSION

Future studies should use standardized quantitative sensory testing protocols with consistent and operationalized definitions of sensitization to provide clear insight about pain processing and central sensitization in sickle cell disease.

Biopsychosocial Factors Associated With Pain and Pain-Related Outcomes in Adults and Children With Sickle Cell Disease: A Multivariable Analysis of the GRNDaD Multicenter Registry

Pain is the primary symptomatic manifestation of sickle cell disease (SCD), an inherited hemoglobinopathy. The characteristics that influence pain experiences and outcomes in SCD are not fully understood. The primary objective of this study was to use multivariable modeling to examine associations of biopsychosocial variables with a disease-specific measure of pain interference known as pain impact. We conducted a secondary analysis of data from the Global Research Network for Data and Discovery national SCD registry. A total of 657 children and adults with SCD were included in the analysis. This sample was 60% female with a median age of 34 (interquartile range 26-42 years) and a chronic pain prevalence of 64%. The model accounted for 58% of the variance in pain impact. Low social (P < .001) and emotional (P < .001) functioning, increasing age (P = .004), low income (P < .001), and high acute painful episodes (P = .007) were most strongly associated with high pain impact in our multivariable model. Additionally, multivariable modeling of pain severity and physical function in 2 comparable samples of registry participants revealed that increasing age and low social functioning were also strongly associated with higher pain severity and low physical functioning. Overall, the results suggest that social and emotional functioning are more strongly associated with pain impact in individuals with SCD than previously studied biological modifiers such as SCD genotype, hemoglobin, and percentage fetal hemoglobin. Future research using longitudinally collected data is needed to confirm these findings. PERSPECTIVE: This study reveals that psychosocial (ie, social and emotional functioning) and demographic (ie, age) variables may play an important role in predicting pain and pain-related outcomes in SCD. Our findings can inform future multicenter prospective longitudinal studies aimed at identifying modifiable psychosocial predictors of adverse pain outcomes in SCD.

Adolescents and Young Adults With Sickle Cell Disease: Nociplastic Pain and Pain Catastrophizing as Predictors of Pain Interference and Opioid Consumption

OBJECTIVES

Some patients with sickle cell disease (SCD) have features of nociplastic pain. While research suggests that many patients with nociplastic pain consume more opioids due to opioid nonresponsiveness, little is known about the impact of nociplastic pain and pain catastrophizing on opioid consumption and pain interference among adolescents and young adults (AYA) with SCD. The purpose of this study was to (1) characterize nociplastic pain and pain catastrophizing among AYA with SCD, and (2) determine whether these characterizations are associated with subsequent opioid consumption and pain interference 1 month after characterization.

METHODS

Participants completed surveys characterizing nociplastic pain and catastrophizing at a routine clinic visit (baseline). Thereafter, participants received weekly text messages that included pain interference and opioid consumption surveys. Multipredictor 2-part models were used to evaluate the predictive relationships between baseline characterizations and subsequent pain interference, and opioid consumption.

RESULTS

Forty-eight AYA aged 14 to 35 completed baseline measures. Twenty-five percent of participants had scores suggestive of nociplastic pain. Greater nociplastic pain features significantly increased the odds of consuming opioids (odds ratio=1.2) and having greater interference from pain (odds ratio=1.46). Regression analyses found that greater baseline nociplastic pain characteristics were significantly associated with opioid consumption (β=0.13) and pain interference (β=0.061); whereas higher pain catastrophizing scores predicted less opioid consumption (β=-0.03) and less pain interference (β=-0.0007).

DISCUSSION

In this sample of AYA with SCD, features of nociplastic pain predicted higher subsequent opioid consumption and pain interference. Being aware of nociplastic pain features in patients with SCD may better guide individualized pain management.

Multimodal phenotyping and correlates of pain following hematopoietic cell transplant in children with sickle cell disease

INTRODUCTION

There is limited understanding of pain, patient-reported outcomes (PROs) of health-related quality of life (HRQoL), psychological factors, and experimental pain sensitivity before and following hematopoietic cell transplant (HCT) in children with sickle cell disease (SCD).

METHODS

Individuals aged 8 years and older, English speaking, and scheduled for a HCT were invited to participate in an observational study where they completed assessments of pain, PROs, psychological factors, and qualitative interviews before and around 3 months, 6 months, 1 year, and 2 years post-HCT. An optional substudy of experimental pain sensitivity before and around 6 month, 1 year, and 2 years post-HCT was also offered.

RESULTS

Data from eight participants (median age 13.5 years, 25% female) with sickle cell anemia (SCA) or similarly severe genotype, and successful donor-derived erythropoiesis post-HCT are reported. We found that collection of pain, PROs, psychological factors, and qualitative data were feasible in the context of HCT. We found moderate to large differences in pain and some PROs between baseline to 1 year and baseline to 2 year post-HCT based on effect sizes, but only some differences were statistically significant. We found moderate to large differences in pressure pain threshold and moderate differences in cold pain threshold between baseline to 1 year and baseline to 2 year post-HCT based on effect sizes, but these differences were not statistically significant. Qualitative data indicated an improvement in pain and HRQoL post-HCT.

CONCLUSION

This study provides a framework for the conduct of multimodal pain assessments before and after HCT, which is feasible but faced with unique barriers.

Long-term alterations in somatosensory functioning in survivors of childhood cancer

ABSTRACT

Cancer and its treatment can have lasting consequences on somatosensation, including pain, which is often underrecognized and undertreated. Research characterizing the impact of cancer on pain and sensory processing in survivors of childhood cancer is scarce. This study aimed to quantify generalized differences in pain and sensory processing in survivors of childhood cancer compared with reference data using a standardized thermal and mechanical quantitative sensory testing (QST) protocol. The association between demographic, clinical (eg, leukemia vs other cancers and treatment exposures), and psychosocial (eg, anxiety and pain catastrophizing) variables and sensitivity to pain and sensory stimuli were also evaluated. Participants were 56 survivors of various types of childhood cancer (52% male, Mage = 13.5 years, SD = 3.2, range = 8-17 years). On average, children were 7 years (SD = 4.1, range = 1.2-16.5) post treatment. Almost all participants (86%) had at least 1 abnormal QST parameter compared with age- and sex-matched reference data; however, few participants self-reported the presence of sensory abnormalities. Generally, participants exhibited reduced sensitivity across the QST parameters examined (Ps < 0.05, ds = 0.40-3.45). A significant minority (45%) also exhibited pain sensitization (P <0.001, d = 0.42). Several risk factors for changes in sensory processing were identified, including current age, history of leukemia, certain treatment exposures (eg, vincristine cumulative dose, major surgery, and bone marrow or stem cell transplant), time off treatment, and higher anxiety and pain catastrophizing scores. Overall, this study demonstrated that somatosensory changes are prevalent in survivors of childhood cancer years after the completion of treatment. Future research is needed to understand long-term implications of altered somatosensation in this complex population.

Clusters of pain trajectories among patients with sickle cell disease hospitalized for vaso-occlusive crisis: a data-driven approach

BACKGROUND

Vaso-occlusive crises (VOC) are the hallmark of sickle cell disease (SCD), with higher severity among hospitalized patients. Clustering hospitalizations with similar pain trajectories could identify vulnerable patient subgroups. Aims were to (1) identify clusters of hospitalizations based on pain trajectories; (2) identify factors associated with these clusters; and (3) determine the association between these clusters and 30-day readmissions.

METHODS

We retrospectively included 350 VOC hospitalizations from 2013-2016 among 59 patients. Finite mixture modeling identified clusters of hospitalizations from intercepts and slopes of pain trajectories during the hospitalization. Generalized estimating equations for multinomial and logistic models were used to identify factors associated with clusters of hospitalizations based on pain trajectories and 30-day readmissions, respectively, while accounting for multiple hospitalizations per patient.

RESULTS

Three clusters of hospitalizations based on pain trajectories were identified: slow (n=99), moderate (n=207), and rapid (n=44) decrease in pain scores. In multivariable analysis, SCD complications, female gender, and affective disorders were associated with clusters with slow or moderate decrease in pain scores (compared to rapid decrease). Although univariate analysis found that the cluster with moderate decrease in pain scores was associated with lower odds of 30-day readmissions compared to the cluster with slow decrease, it was non-significant in multivariable analysis. SCD complications were associated with higher odds of 30-day readmissions and older age was associated with lower odds of 30-day readmissions.

CONCLUSIONS

Our results highlight variability in pain trajectories among patients with SCD experiencing VOC and provide a novel approach for identifying subgroups of patients that could benefit from more intensive follow-up.

Spatiotemporal Alterations in Gait in Humanized Transgenic Sickle Mice

Sickle cell disease (SCD) is a hemoglobinopathy affecting multiple organs and featuring acute and chronic pain. Purkinje cell damage and hyperalgesia have been demonstrated in transgenic sickle mice. Purkinje cells are associated with movement and neural function which may influence pain. We hypothesized that Purkinje cell damage and/or chronic pain burden provoke compensatory gait changes in sickle mice. We found that Purkinje cells undergoe increased apoptosis as shown by caspase-3 activation. Using an automated gait measurement system, MouseWalker, we characterized spatiotemporal gait characteristics of humanized transgenic BERK sickle mice in comparison to control mice. Sickle mice showed alteration in stance instability and dynamic gait parameters (walking speed, stance duration, swing duration and specific swing indices). Differences in stance instability may reflect motor dysfunction due to damaged Purkinje cells. Alterations in diagonal and all stance indices indicative of hesitation during walking may originate from motor dysfunction and/or arise from fear and/or anticipation of movement-evoked pain. We also demonstrate that stance duration, diagonal swing indices and all stance indices correlate with both mechanical and deep tissue hyperalgesia, while stance instability correlates with only deep tissue hyperalgesia. Therefore, objective analysis of gait in SCD may provide insights into neurological impairment and pain states.

Characterizing Clinical Features and Creating a Gene Expression Profile Associated With Pain Burden in Children With Inflammatory Bowel Disease

BACKGROUND

There is often dissociation between inflammatory activity and abdominal pain in children with inflammatory bowel disease (IBD), suggesting other factors may play a role in the pain experience.

METHODS

Patients (8 to 17 years) newly diagnosed with IBD were enrolled in the ALLAY Study: Assessing Risk Factors for Abdominal Pain in Children with Inflammatory Bowel Disease (NCT02984059). At diagnostic colonoscopy, 3 rectal biopsies were collected, and gene expression analysis was performed using Qiagen RT2 Profiler Neuropathic and Inflammatory Pain PCR Array. Relative fold difference in gene expression for 84 pain-associated genes was calculated using the 2-ΔΔ Cq method compared with pain-free controls. Factors affecting pain burden (Pain Burden Interview; PBI) were analyzed, including age, sex, rectal inflammation, and gene expression. Data were analyzed using multiple stepwise linear regression and 2-tailed t tests (P ≤ 0.05).

RESULTS

Thirty-nine newly diagnosed IBD patients were included (65% male, mean age 12.75 years [SD 2.63], 23 Crohn's disease, 16 ulcerative colitis), along with 3 controls. Mean PBI score was 7.73 (SD 6.4, range 0 to 23) for all patients. Age and sex were not predictive of pain burden, but disease activity score was (P = 0.03). Expression of TRPV3, OPRM1, P2X3, SCN9A, PTGS2, and MAPK14 were associated with PBI score. Subsequent 2-tailed t tests comparing patients with no pain (PBI score ≦ 2, N = 11) to those with pain (PBI > 2, N = 28) confirmed differential expression of TRPV3, PTGS2, and MAPK14 was in patients with pain (all P < 0.05).

CONCLUSION

Pain burden in newly diagnosed IBD patients may be linked to TRPV3, PTGS2, and MAPK14 expression, suggesting potential therapeutic targets for managing pain in IBD.

Systematic Review: Pain and Emotional Functioning in Pediatric Sickle Cell Disease

The objective of this systematic review was to assess the relationship between pain (frequency/intensity/duration, impairment, coping) and emotional functioning in pediatric Sickle Cell Disease, and evaluate the state of the literature. Studies were included if they met each of the following criteria: (a) primarily pediatric sample of youth or young adults up to age 21 years with SCD, (b) examined emotional functioning including anxiety and/or depressive and/or internalizing symptoms, and/or affect, (c) examined pain intensity/frequency/duration and/or pain-related impairment and/or pain coping as it relates to emotional functioning, as defined above. Using the established guidelines for systematic reviews, we searched PsycINFO, PubMED, and CINAHL databases for studies published through June 2018. Screening resulted in 33 studies meeting inclusion criteria. Study data were extracted and evaluated for scientific merit, resulting in four studies being removed. 29 studies were included in the final synthesis. Studies provide strongest evidence of a relationship between increased pain frequency and higher depressive and anxiety symptoms. There are moderate-to-strong associations between pain-related impairment and depressive symptoms, and small-to-strong associations between pain-related impairment and anxiety. When examining pain-coping strategies, maladaptive cognitive strategies show the strongest association with emotional functioning. There is a need for more adequately powered, prospective studies based on theoretical frameworks in order to advance our understanding of the relationship between pain and emotional functioning in pediatric SCD.

New and emerging treatments for vaso-occlusive pain in sickle cell disease

Introduction: Acute pain from episodic vaso-occlusion (VOC) spans the lifespan of almost everyone with sickle cell disease (SCD), while additional chronic pain develops in susceptible individuals in early adolescences. Frequent acute pain with chronic pain causes significant physical and psychological morbidity, and frequent health-care utilization. Available pharmacologic therapies reduce acute pain frequency but few evidence-based therapies are available for chronic pain. Areas covered: An extensive PubMed literature search was performed with appropriate search criteria. The pathophysiology of acute pain from VOC in SCD is very complex with many events subsequent to sickle polymer formation. Sensitization of pain pathways and alterations of brain networks contributes to the experience of chronic pain. Numerous therapies targeting putative VOC mechanisms are in clinical trials, and show considerable promise. Alternative analgesic treatments for acute and chronic pain have been examined in small patient cohorts, but formal clinical trials are lacking. Expert opinion: Childhood is likely a critical window for prevention of acute and later chronic pain. New multimodal analgesic therapies are needed, particularly for chronic pain, and should be examined in clinical trials. Given the multifactorial nature of both pain and VOC, simultaneously targeting multiple mechanisms may be the optimal approach for effective preventive therapies.

Quantitative sensory testing in children with sickle cell disease: additional insights and future possibilities

Quantitative sensory testing (QST) is used in a variety of pain disorders to characterize pain and predict prognosis and response to specific therapies. In this study, we aimed to confirm results in the literature documenting altered QST thresholds in sickle cell disease (SCD) and assess the test-retest reliability of results over time. Fifty-seven SCD and 60 control subjects aged 8-20 years underwent heat and cold detection and pain threshold testing using a Medoc TSAII. Participants were tested at baseline and 3 months; SCD subjects were additionally tested at 6 months. An important facet of our study was the development and use of a novel QST modelling approach, allowing us to model all data together across modalities. We have not demonstrated significant differences in thermal thresholds between subjects with SCD and controls. Thermal thresholds were consistent over a 3- to 6-month period. Subjects on whom hydroxycarbamide (HC) was initiated shortly before or after baseline testing (new HC users) exhibited progressive decreases in thermal sensitivity from baseline to 6 months, suggesting that thermal testing may be sensitive to effective therapy to prevent vasoocclusive pain. These findings inform the use of QST as an endpoint in the evaluation of preventative pain therapies.

Multiple psychological factors predict abdominal pain severity in children with irritable bowel syndrome

BACKGROUND

Anxiety and depression are implicated as contributors to abdominal pain in pediatric irritable bowel syndrome (IBS) but is unclear if this pain is associated with other psychological factors. The study objective was to test if the impact of anxiety or depression on IBS symptom severity is mediated by somatization and/or pain catastrophizing.

METHODS

We utilized baseline data from local pediatric IBS clinical studies. Through mediation analysis, we assessed whether somatization or pain catastrophizing mediated (either independently or combined) the separate relationships of anxiety or depression with IBS abdominal pain severity.

KEY RESULTS

We analyzed 261 participants. All psychological factors were positively correlated with one another and IBS abdominal pain severity. The association of anxiety with IBS abdominal pain was mediated by both somatization and pain catastrophizing in individual analyses (each mediated standardized coefficient [β] 0.11, CI 0.05-0.18) and in multiple analysis (mediated standardized β 0.18, CI 0.09-0.27). The association of depression with IBS abdominal pain was also mediated by somatization (mediated standardized β 0.08, CI0.02-0.14) and pain catastrophizing (mediated standardized β 0.06, CI 0.01-0.11) in individual analyses and in multiple analysis (mediated standardized β 0.19, CI 0.04-0.19).

CONCLUSIONS AND INFERENCES

Somatization and pain catastrophizing mediate the relationships between anxiety/depression and IBS abdominal pain severity. These findings suggest that somatization and pain catastrophizing may be better treatment targets than anxiety and depression. Clinicians should assess these psychological factors in pediatric IBS patients and refer for intervention to improve outcomes.

Psychological Predictors of Pain in Children and Adolescents With Sickle Cell Disease: A Scoping Review

Objective: Sickle cell disease (SCD) is a common red blood cell disorder that disrupts the lives of many African Americans and those of Middle Eastern heritage within the United States due to frequent pain. There is limited research quantifying biopsychosocial factors, specifically psychological characteristics, that influence pain in children and adolescents with SCD. The aim of this literature review was to identify psychological characteristics that are predictive or associated with pain in children and adolescents with SCD. Method: This review was conducted using PRISMA guidelines. Four databases, PubMed, CINAHL, PsycINFO, and Scopus, were searched using specific terms to address the aim of the review (SCD, pain, pediatrics and adolescents, and psychological characteristics). Results: The review identified a lack of consensus regarding the definitions and measurement of pain frequency and intensity. A variety of psychological characteristics were associated with pain including coping strategies, anxiety, depressive symptoms, catastrophizing, and stress. Overall, the study designs restricted the ability to fully identify psychological characteristics that predict pain. Conclusions: Health science researchers must strive for a deeper understanding about the presentation of SCD pain and psychological risk factors associated with increased pain to provide targeted screening and treatment.

Pain catastrophizing is associated with poorer health-related quality of life in pediatric patients with sickle cell disease

Background

Sickle cell disease (SCD) is an inherited disorder of the red blood cells and is associated with chronic multisystem involvement. While SCD has been associated with poorer health-related quality of life (HRQoL), there is a paucity of data on the relationship of psychological covariates other than anxiety and depression and quality of life (QoL) in children with SCD.

Materials and methods

We performed a cross-sectional study of psychological factors, HRQoL, and pain-related outcomes in participants with SCD and race-matched controls as part of a larger study of experimental pain phenotyping.

Results

Pain catastrophizing was inversely correlated with HRQoL measured by the PedsQL™ Generic Core Scale in children with SCD, while this was not noted in control participants. Psychological factors, such as anxiety and depressive symptoms, were also associated with poorer HRQoL in both children with SCD and controls. We did not find an association of psychological factors with prior health care utilization. Psychological factors such as anxiety and depressive symptoms were inversely correlated with pain interference, but not pain intensity in SCD.

Conclusion

Catastrophizing is associated with poorer HRQoL in SCD, but in this study, it was not associated with pain intensity or interference and health care utilization in children with SCD. Further studies are needed to fully define the association of psychological factors including catastrophizing with QoL, pain burden, and SCD outcomes.

Small-fiber neuropathy and pain sensitization in survivors of pediatric acute lymphoblastic leukemia

BACKGROUND

Chemotherapy-induced Peripheral Neuropathy (CIPN) of large-fibers affects up to 20% of survivors of pediatric acute lymphoblastic leukemia (ALL). We aimed to describe small-fiber toxicity and pain sensitization in this group.

METHODS

In a cross-sectional, bicentric study we assessed 46 survivors of pediatric ALL (Mean age: 5.7 ± 3.5 years at diagnosis, median 2.5 years after therapy; males: 28).

INCLUSION CRITERIA

≥6 years of age, ≥3 months after last administration of Vincristine, and cumulative dose of Vincristine 12 mg/m². We used a reduced version of the Pediatric-modified Total Neuropathy Score (Ped-mTNS) as bedside test and Quantitative Sensory Testing (QST) for assessment of small- and large-fiber neuropathy as well as pain sensitization. We employed Nerve Conduction Studies (NCS) as the most accurate tool for detecting large-fiber neuropathy.

RESULTS

Fifteen survivors (33%) had abnormal rPed-mTNS values (≥4 points) and 5 survivors (11%) reported pain. In QST, the survivor group showed significant (p < 0.001) inferior large-fiber function and pain sensitization when compared to healthy matched peers. We identified deficits of vibration in 33 (72%) and tactile hypoesthesia in 29 (63%), hyperalgesia to blunt pressure in 19 (41%), increased mechanical pain sensitivity in 12 (26%) and allodynia in 16 (35%) of 46 survivors. Only 7 survivors (15%) had pathologic NCS.

CONCLUSION

QST is a sensitive tool that revealed signs of large-fiber neuropathy in two thirds, small-fiber neuropathy and pain sensitization in one third of survivors. Prospective studies using QST in pediatric oncology may help to elucidate the pathophysiology of small-fiber neuropathy and pain sensitization as well as their relevance for quality of survival.

Sickle cell disease

Sickle cell disease (SCD) is a group of inherited disorders caused by mutations in HBB, which encodes haemoglobin subunit β. The incidence is estimated to be between 300,000 and 400,000 neonates globally each year, the majority in sub-Saharan Africa. Haemoglobin molecules that include mutant sickle β-globin subunits can polymerize; erythrocytes that contain mostly haemoglobin polymers assume a sickled form and are prone to haemolysis. Other pathophysiological mechanisms that contribute to the SCD phenotype are vaso-occlusion and activation of the immune system. SCD is characterized by a remarkable phenotypic complexity. Common acute complications are acute pain events, acute chest syndrome and stroke; chronic complications (including chronic kidney disease) can damage all organs. Hydroxycarbamide, blood transfusions and haematopoietic stem cell transplantation can reduce the severity of the disease. Early diagnosis is crucial to improve survival, and universal newborn screening programmes have been implemented in some countries but are challenging in low-income, high-burden settings.

Quantitative sensory testing is feasible and is well-tolerated in patients with sickle cell disease following a vaso-occlusive episode

Introduction

Sickle cell disease (SCD) is an inherited blood disorder characterized by abnormally shaped sickle cells. The hallmark of this disease is intermittent, painful vaso-occlusive episodes (VOE), but a subset of individuals with SCD experience chronic pain. The mechanism of transition to chronic pain is not well understood in SCD, but there is evidence of altered pain processing in individuals with SCD. The impact of VOE on pain sensitivity is not established. The objective of this study was to determine the feasibility and tolerability of quantitative sensory testing (QST) in SCD following a VOE to better understand the contribution of VOE to the development of chronic pain.

Methods

As part of a larger pain sensitivity study, pediatric patients with SCD were offered QST following a VOE-related Emergency Room visit or inpatient hospitalization. The feasibility of recruitment and completion of QST was measured, and tolerability of QST was determined using post-QST assessments of pain, and compared with measurements at steady state.

Results

Ten participants completed QST following a VOE. The median age was 16.5, and 60% were female. Overall, 10 of 16 (62.5%) patients approached for QST following VOE completed QST. This included 8 of 12 patients who had previously completed QST at steady state. There were no statistically significant differences in pain intensity and Gracely Box scores after QST following a VOE, when compared to steady-state QST.

Conclusion

QST is feasible and is well-tolerated following a VOE in patients with SCD. Large prospective studies are needed to determine the impact of VOE on experimental pain sensitivity and must take into account all factors contributing to pain sensitivity.

Does Transcranial Direct Current Stimulation Combined with Peripheral Electrical Stimulation Have an Additive Effect in the Control of Hip Joint Osteonecrosis Pain Associated with Sickle Cell Disease? A Protocol for a One-Session Double Blind, Block-Randomized Clinical Trial

Chronic pain in Sickle Cell Disease (SCD) is probably related to maladaptive plasticity of brain areas involved in nociceptive processing. Transcranial Direct Current Stimulation (tDCS) and Peripheral Electrical Stimulation (PES) can modulate cortical excitability and help to control chronic pain. Studies have shown that combined use of tDCS and PES has additive effects. However, to date, no study investigated additive effects of these neuromodulatory techniques on chronic pain in patients with SCD. This protocol describes a study aiming to assess whether combined use of tDCS and PES more effectively alleviate pain in patients with SCD compared to single use of each technique. The study consists of a one-session double blind, block-randomized clinical trial (NCT02813629) in which 128 participants with SCD and femoral osteonecrosis will be enrolled. Stepwise procedures will occur on two independent days. On day 1, participants will be screened for eligibility criteria. On day 2, data collection will occur in four stages: sample characterization, baseline assessment, intervention, and post-intervention assessment. These procedures will last ~5 h. Participants will be divided into two groups according to homozygous for S allele (HbSS) (n = 64) and heterozygous for S and C alleles (HbSC) (n = 64) genotypes. Participants in each group will be randomly assigned, equally, to one of the following interventions: (1) active tDCS + active PES; (2) active tDCS + sham PES; (3) sham tDCS + active PES; and (4) sham tDCS + sham PES. Active tDCS intervention will consist of 20 min 2 mA anodic stimulation over the primary motor cortex contralateral to the most painful hip. Active PES intervention will consist of 30 min sensory electrical stimulation at 100 Hz over the most painful hip. The main study outcome will be pain intensity, measured by a Visual Analogue Scale. In addition, electroencephalographic power density, cortical maps of the gluteus maximus muscle elicited by Transcranial Magnetic Stimulation (TMS), serum levels of Brain-derived Neurotrophic Factor (BDNF), and Tumor Necrosis Factor (TNF) will be assessed as secondary outcomes. Data will be analyzed using ANOVA of repeated measures, controlling for confounding variables.