Common Pediatric Pain Disorders and Their Clinical Associations

Sex-specific patterns of discomfort in patients with restless legs syndrome

STUDY OBJECTIVES

Sex differences in the prevalence of restless legs syndrome (RLS) have been reported, with a higher prevalence in women than in men. However, sex differences in clinical presentation remain unclear. We aimed to investigate the phenotypic differences in patients with RLS between sexes by comparing clinical presentations, iron status, polysomnographic parameters, and treatment.

METHODS

We retrospectively evaluated 614 patients (225 men, 389 women) diagnosed with RLS. To enhance the robustness of the study, an age-matched control group of 179 men and 286 women without sleep disorders was also included. Information on demographics and sleep-related questionnaires were collected. Iron status was evaluated using blood samples, and polysomnography was performed to evaluate periodic leg movements and comorbid sleep disorders.

RESULTS

Our analysis revealed no sex difference in the severity of RLS but a difference in the pattern of symptoms. Women had more frequent symptoms of pain and awakening during sleep, while men had more common motor symptoms (both self-reported symptoms and periodic leg movement on polysomnography). Women with RLS also had lower iron parameters and received more frequent iron supplementation therapy than men. In contrast to women with RLS, who presented higher sleep disturbances and depressive mood, men with RLS had a higher risk of comorbidities such as hypertension and cardiovascular disease. These sex differences were notably more pronounced than in the control group.

CONCLUSIONS

This study suggests that sex differences exist in RLS phenotypes, and clinicians should consider these differences for treatment.

CITATION

Kim J, Kim JR, Park HR, Joo EY. Sex-specific patterns of discomfort in patients with restless legs syndrome. J Clin Sleep Med. 2024;20(2):253-259.

Early-Life Iron Deficiency Persistently Alters Nociception in Developing Mice

Clinical association studies have identified early-life iron deficiency (ID) as a risk factor for the development of chronic pain. While preclinical studies have shown that early-life ID persistently alters neuronal function in the central nervous system, a causal relationship between early-life ID and chronic pain has yet to be established. We sought to address this gap in knowledge by characterizing pain sensitivity in developing male and female C57Bl/6 mice that were exposed to dietary ID during early life. Dietary iron was reduced by ∼90% in dams between gestational day 14 and postnatal day (P)10, with dams fed an ingredient-matched, iron-sufficient diet serving as controls. While cutaneous mechanical and thermal withdrawal thresholds were not altered during the acute ID state at P10 and P21, ID mice were more sensitive to mechanical pressure at P21 independent of sex. During adulthood, when signs of ID had resolved, mechanical and thermal thresholds were similar between early-life ID and control groups, although male and female ID mice displayed increased thermal tolerance at an aversive (45 °C) temperature. Interestingly, while adult ID mice showed decreased formalin-induced nocifensive behaviors, they showed exacerbated mechanical hypersensitivity and increased paw guarding in response to hindpaw incision in both sexes. Collectively, these results suggest that early-life ID elicits persistent changes in nociceptive processing and appears capable of priming developing pain pathways. PERSPECTIVE: This study provides novel evidence that early-life ID evokes sex-independent effects on nociception in developing mice, including an exacerbation of postsurgical pain during adulthood. These findings represent a critical first step towards the long-term goal of improving health outcomes for pain patients with a prior history of ID.

Back Pain without Disease or Substantial Injury in Children and Adolescents: A Twin Family Study Investigating Genetic Influence and Associations

This twin family study first aimed to investigate the evidence for genetic factors predicting the risk of lifetime prevalence of non-specific low back pain of at least three months duration (LBP (life)) and one-month current prevalence of thoracolumbar back pain (TLBP (current)) using a study of children, adolescents, and their first-degree relatives. Secondly, the study aimed to identify associations between pain in the back with pain in other regions and also with other conditions of interest. Randomly selected families (n = 2479) with child or adolescent twin pairs and their biological parents and first siblings were approached by Twins Research Australia. There were 651 complete twin pairs aged 6-20 years (response 26%). Casewise concordance, correlation, and odds ratios were compared for monozygous (MZ) and dizygous (DZ) pairs to enable inference about the potential existence of genetic vulnerability. Multivariable random effects logistic regression was used to estimate associations between LBP (life) or TLBP (current) as an outcome with the potentially relevant condition as predictors. The MZ pairs were more similar than the DZ pairs for each of the back pain conditions (all p values < 0.02). Both back pain conditions were associated with pain in multiple sites and with primary pain and other conditions using the combined twin and sibling sample (n = 1382). Data were consistent with the existence of genetic influences on the pain measures under the equal environments assumption of the classic twin model and associations with both categories of back pain were consistent with primary pain conditions and syndromes of childhood and adolescence which has research and clinical implications.

Anxiety and Depressive Symptoms and Disorders in Children and Adolescents With Migraine: A Systematic Review and Meta-analysis

Importance

Though it is presumed that children and adolescents with migraine are at risk of internalizing symptoms and disorders, high-level summative evidence to support this clinical belief is lacking.

Objective

To determine if there is an association between internalizing symptoms and disorders and migraine in children and adolescents.

Data Sources

A librarian-led, peer-reviewed search was performed using MEDLINE, Embase, PsycINFO, and CINAHL databases (inception to March 28, 2022).

Study Selection

Case-control, cohort, and cross-sectional studies on the association between internalizing symptoms and disorders and migraine in children and adolescents 18 years or younger were eligible.

Data Extraction and Synthesis

Two investigators independently completed abstract and full-text screening, data extraction, and quality appraisal using the Newcastle-Ottawa scales. Studies were pooled with random-effects meta-analyses using standardized mean differences (SMD) or odds ratios (OR) with 95% CIs. Where sufficient data for pooling were unavailable, studies were described qualitatively.

Main Outcomes and Measures

The primary outcome was migraine diagnosis; additional outcomes included migraine outcomes and incidence. Associations between these outcomes and internalizing symptoms and disorders were evaluated.

Results

The study team screened 4946 studies and included 80 studies in the systematic review. Seventy-four studies reported on the association between internalizing symptoms and disorders and migraine, and 51 studies were amenable to pooling. Meta-analyses comparing children and adolescents with migraine with healthy controls showed: (1) an association between migraine and anxiety symptoms (SMD, 1.13; 95% CI, 0.64-1.63); (2) an association between migraine and depressive symptoms (SMD, 0.67; 95% CI, 0.46-0.87); and (3) significantly higher odds of anxiety disorders (OR, 1.93, 95% CI, 1.49-2.50) and depressive disorders (OR, 2.01, 95% CI, 1.46-2.78) in those with, vs without, migraine. Stratification of results did not reveal differences between clinical vs community/population-based samples and there was no evidence of publication bias. Twenty studies assessing the association between internalizing symptoms or disorders and migraine outcomes (n = 18) or incident migraine (n = 2) were summarized descriptively given significant heterogeneity, with minimal conclusions drawn.

Conclusions and Relevance

In this study, children and adolescents with migraine were at higher risk of anxiety and depression symptoms and disorders compared with healthy controls. It may be beneficial to routinely screen children and adolescents with migraine for anxiety and depression in clinical practice. It is unclear whether having anxiety and depressive symptoms or disorders has an affect on migraine outcomes or incidence.

Primary dysmenorrhoea in adolescents and young women: A twin family study of maternal transmission, genetic influence and associations

AIMS

The extent to which maternal transmission of primary dysmenorrhoea is genetically determined in adolescents and young women has yet to be determined. We aimed to assess heritability and associations relevant to primary pain syndromes using a twin family study.

METHODS

Participants were young menstruating female twins, and their oldest sisters and mothers, whose families were registered with Twins Research Australia and previously participated in a twin family study of primary paediatric pain disorders. Questionnaire packs were mailed, assessing current maximum and average menstrual pain intensity, current pain interference with activities and retrospective dysmenorrhea secondary symptoms.

RESULTS

The sample comprised 206 twin individuals (57 monozygous (MZ) and 46 dizygous (DZ) pairs) aged 10-22 years, eldest siblings (n = 38) aged 13-28 years and mothers (n = 101) aged 32-61 years. The estimated regression coefficient of the relationship between mother-daughter and twin-sibling dyads indicated significant associations for the measures of dysmenorrhea and supported heritability. Adjusted for age, the within twin-pair correlation for MZ twins was generally more than twice that of DZ twins. Heritability estimates were maximal pain intensity 0.67 (P = 3.8 × 10^-11 ), average pain intensity 0.63 (P = 3.7 × 10^-10 ), pain interference 0.57 (P = 1.8 × 10^-8 ) and retrospective symptoms 0.57 (P = 1.8 × 10^-8 ). Twin individuals with a lifetime (three-month) history of iron deficiency and those with painless restless legs syndrome (RLS) were significantly more likely to have more intense pain associated with menstruation.

CONCLUSION

Primary dysmenorrhea in adolescents and young women was shown to be relatively strongly genetically influenced and associated especially with a history of iron deficiency and painless RLS which have potential therapeutic implications.

Defining Growing Pains: A Scoping Review

BACKGROUND AND OBJECTIVES

Up to one third of children may be diagnosed with growing pains, but considerable uncertainty surrounds how to make this diagnosis. The objective of this study was to detail the definitions of growing pains in the medical literature.

METHODS

Scoping review with 8 electronic databases and 6 diagnostic classification systems searched from their inception to January 2021. The study selection included peer-reviewed articles or theses referring to "growing pain(s)" or "growth pain(s)" in relation to children or adolescents. Data extraction was performed independently by 2 reviewers.

RESULTS

We included 145 studies and 2 diagnostic systems (ICD-10 and SNOMED). Definition characteristics were grouped into 8 categories: pain location, age of onset, pain pattern, pain trajectory, pain types and risk factors, relationship to activity, severity and functional impact, and physical examination and investigations. There was extremely poor consensus between studies as to the basis for a diagnosis of growing pains. The most consistent component was lower limb pain, which was mentioned in 50% of sources. Pain in the evening or night (48%), episodic or recurrent course (42%), normal physical assessment (35%), and bilateral pain (31%) were the only other components to be mentioned in more than 30% of articles. Notably, more than 80% of studies made no reference to age of onset in their definition, and 93% did not refer to growth. Limitations of this study are that the included studies were not specifically designed to define growing pains.

CONCLUSIONS

There is no clarity in the medical research literature regarding what defines growing pain. Clinicians should be wary of relying on the diagnosis to direct treatment decisions.

Improved definition of growing pains: A common familial primary pain disorder of early childhood

Background

Commonly applied diagnostic criteria for growing pains (GP) have evolved without determination by an authoritative representative body. GP and restless legs syndrome (RLS) share anatomical, distributional, temporal, and other clinical features and are associated in individuals over time, in families, and in population samples. In this study, we tested the hypothesis that GP, diagnosed by widely used criteria, is confounded by cases of painful restless legs syndrome (RLS‐Painful).

Methods

A twin family study of genetic influence and associations of GP using questionnaires was administered by Twins Research Australia. Twins (3–18 years; monozygous 503, dizygous 513), their oldest siblings, mothers, and fathers were randomly selected from the twin registry. Family members completed the questionnaires assessing lifetime prevalence of GP by commonly applied criteria and covariates including the history of iron deficiency and pediatric pain disorders. A GP‐Specific phenotype was defined as GP without urge to move the legs. We determined similarities in twin pairs for the GP and GP‐Specific phenotypes, family associations, and estimated familial and individual‐specific associations for each phenotype.

Results

Lifetime prevalence was one‐third lower for GP‐Specific than for GP among the twin and family members. Monozygous twin pairs were more similar than dizygous twin pairs for GP and for the derived GP‐Specific phenotype by three methods, consistent with genetic influence. There were familial associations, but the essential evidence for genetic influence was the twin‐cotwin data. GP was associated, in multivariable analyses, with migraine, headaches, recurrent abdominal pain, and iron deficiency, while GP‐Specific associations were limited to migraine and headaches.

Conclusions

GP is hybrid, one‐third of cases having symptoms and associations of RLS, necessarily RLS‐Painful. GP‐Specific (without symptoms and associations of RLS) could have a genetic etiology. We propose new criteria to facilitate etiological and therapeutic research.

Growing pains, a highly prevalent primary pain disorder of childhood, has been associated with restless legs syndrome in individuals over time, in families and in population samples. This conundrum has been clarified by the evidence in this twin family study that growing pains, as previously defined, has been confounded by symptoms of restless legs syndrome. An exclusion clause of urge to move the legs has resulted in criteria for a purer phenotype which retains evidence of heritability.

Adolescent pain: appraisal of the construct and trajectory prediction-by-symptom between age 12 and 17 years in a Canadian twin birth cohort

ABSTRACT

Adolescent pain is common and continues into adulthood, leading to negative long-term outcomes including substance-related morbidity: an empirical definition of its construct may inform the early detection of persistent pain trajectories. These secondary analyses of a classical twin study assessed whether: headaches, back pains, abdominal pain, chest pains, stabbing/throbbing pain, gastric pain/nausea, measured in 501 pairs across 5 waves between age 12-17, fit a unitary construct, or constitute independent manifestations. We then assessed which symptoms were associated with a steady, 'frequent pain' trajectory that is associated with risk for early opioid prescriptions. Item Response Theory results indicated that all 6 pain symptoms index a unitary construct. Binary logistic regressions identified 'back pain' as the only symptom consistently associated with membership in the 'frequent adolescent pain' trajectory (OR:1.66-3.38) at all 5 measurement waves. Receiver Operating Characteristic analyses computed the discriminating power of symptoms to determine participants' membership into the 'frequent' trajectory: they yielded acceptable (.7-.8) to excellent (.8-.9) area under the curve (AUC) values for all 6 symptoms. The highest AUC was attained by 'back pain' at age 14 (.835); for multiple cut-off thresholds of symptom frequency, 'back pain' showed good sensitivity/false alarm probability trade-offs, predominantly in the 13-14-15 age range, to predict the 'frequent pain' trajectory. These data support a unitary conceptualization and assessment of adolescent pain, which is advantageous for epidemiological, clinical, and translational purposes. Persistent back pain constitutes a sensitive indicator of a steady trajectory of adolescent pain.

Familial and Genetic Influences on the Common Pediatric Primary Pain Disorders: A Twin Family Study

The primary pain disorders of childhood are highly prevalent but have infrequently been studied collectively. Genetic influences have been suggested to be causally implicated. Surveys were sent to 3909 Australian twin families, assessing the lifetime prevalence of growing pains, migraine, headache, recurrent abdominal pain, low back pain, and persistent pain (not otherwise specified) in pediatric twins and their immediate family members. Comparisons between monozygous (MZ) and dizygous (DZ) twin pair correlations, concordances and odds ratios were performed to assess the contribution of additive genetic influences. Random-effects logistic regression modelling was used to evaluate relationships between twin individuals and their co-twins, mothers, fathers and oldest siblings with the subject conditions. Twin analyses of responses from 1016 families revealed significant influence of additive genetic effects on the presence of growing pains, migraine, and recurrent abdominal pain. The analyses for headache, low back pain, and persistent pain overall did not conclusively demonstrate that genetic influences were implicated more than shared environmental factors. Regression analyses demonstrated varying levels of significance in relationships between family members and twin individuals for the tested conditions, with strongest support for genetic influences in growing pains and migraine. These data, together with previously published association analyses, suggest common causal influences including genes.

Trajectories of pain and anxiety in a longitudinal cohort of adolescent twins

BACKGROUND

Adolescence is critical to intercept chronic/persistent pain and decipher its association with anxiety. We ascertained adolescent pain trajectories, their demographic and clinical correlates, the longitudinal association with opiate prescriptions at age 19, and the etiology of the covariation between adolescent pain problems and anxiety symptoms.

METHODS

Longitudinal assessment of: 6 common pain problems at age 12, 13, 14, 15, and 17 years; 7 common anxiety symptoms at age 12, 13, and 14 years; opiates' prescriptions at age 19, in the Quebec Newborn Twin Study birth cohort of 667 twin pairs born between 1995-1998.

RESULTS

Analyses yielded three trajectories of: "none-to-minimal" (34.3%), "sporadic" (56.7%), and "frequent" (9.0%) pain problems between age 12-17. Anxiety (odds ratios [OR] OR_age12 : 2.38; confidence interval [CI]: 1.26-4.47; OR_age13 : 3.96; CI: 1.73-9.05; OR_age14 : 5.45; CI: 2.67-11.11), the female sex (OR: 3.69; CI: 2.20-6.21), and lower socioeconomic status (OR: 0.87; CI: 0.77-0.98) were associated with the "frequent" compared to the "none-to-minimal" pain trajectory. Only the "frequent" pain trajectory predicted opioid prescriptions at age 19 (OR: 4.14; CI: 1.16-14.55). A twin bivariate latent growth curve model and a cross-lagged model showed that genetic factors and non-shared environmental factors common to both phenotypes influence the longitudinal association between anxiety and adolescent pain problems.

CONCLUSIONS

The relatively common, adolescent "frequent pain" trajectory predicts early opioid prescriptions, and anxiety and adolescent pain share multiple etiological components. These data can inform diagnostic reasoning, clinical practice, and help reducing opioid prescriptions and abuse.

Use of a Probiotic to Enhance Iron Absorption in a Randomized Trial of Pediatric Patients Presenting with Iron Deficiency

OBJECTIVE

To evaluate the efficacy of low dose ferrous sulfate for the treatment of iron deficiency and if the probiotic Lactobacillus plantarum 299v (LP299v) enhances treatment.

STUDY DESIGN

This randomized, double-blinded, controlled trial of the treatment of iron deficiency in children compared the use of low-dose ferrous sulfate (1-3 mg/kg/day), with or without probiotic (LP299v).

RESULTS

Serum ferritin level increased in all children from a baseline of 23.7 ng/mL to 45.4 ng/mL after 6-8 weeks of treatment. There was no significant difference in the increase in serum ferritin in children taking the probiotic LP299v compared with controls (23.2 vs 20.0 ng/mL, respectively). Additionally, an increase in ferritin level was not significantly associated with probiotic use when controlling for other factors, including child weight and dosing. Overall, the treatments were well-tolerated, with mild side effects.

CONCLUSIONS

Treatment with low-dose ferrous sulfate is well-tolerated and effective in correcting iron deficiency in children. However, the probiotic LP299v did not enhance treatment. Further attention should examine the dose-response effect in children, including an alternate day dosing schedule.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01617044.

Flexion-Relaxation Phenomenon in Children and Adolescents With and Without Nonspecific Chronic Low Back Pain: An Electromyographic and Kinematic Cross-Sectional Comparative Study

STUDY DESIGN

A cross-sectional comparative study.

OBJECTIVE

This study aimed to investigate the flexion-relaxation phenomenon (FRP), in standing trunk flexion and slumped sitting tasks, by comparing children and adolescents suffering from nonspecific chronic low back pain (NSCLBP) with controls (CTRL).

SUMMARY OF BACKGROUND DATA

The absence of the FRP can accurately discriminate adults with NSCLBP from those without during standing trunk flexion and slumped sitting tasks. Even if the FRP has been extensively studied in adults with NSCLBP, only one study has evaluated the FRP in adolescents, during a slumped sitting task, and this suggested that the FRP was also present in adolescents with NSCLBP.

METHODS

Thirty-seven children and adolescents with NSCLBP and 23 CTRL performed standing trunk flexion and slumped sitting tasks. All participants were equipped with surface electromyography (EMG) electrodes on the erector spinae longissimus (ESL) and multifidus (M) muscles and reflective markers on the spinous processes of C7, L1, and S1. Global (C7-S1), thoracic (C7-L1), and lumbar (L1-S1) trunk flexion absolute angle were measured. The FRP was reported using visual inspection and a flexion-relaxation ratio (FRR). A self-reference threshold was used to identify the time of FRP onset. Repeated-measures analysis of variance (ANOVA) was used to determine the main and interaction effects of task, group and muscle on FRR, and the relative maximal angle at FRP onset of the global trunk (C7-S1).

RESULTS

Results showed three main findings: (1) the FRP's low sensitivity in discriminating between NSCLBP and CTRL participants in groups, tasks, or muscles; (2) similar observed maximal flexion angles in both groups during flexion tasks; and (3) similar observed relative maximal global trunk flexion angles at FRP onset in groups, tasks, and muscles.

CONCLUSION

These results are not consistent with the literature on adults and could lead to modified therapeutic management of NSCLBP in children and adolescents.

LEVEL OF EVIDENCE

3.