Decreased sensitivity to thermal stimuli in adolescents with autism spectrum disorder: relation to symptomatology and cognitive ability.

UNLABELLED: Social communication deficits and repetitive behaviors are established characteristics of autism spectrum disorder (ASD) and the focus of considerable study. Alterations in pain sensitivity have been widely noted clinically but remain understudied and poorly understood. The ASD population may be at greater risk for having their pain undermanaged, especially in children with impaired cognitive ability and limited language skills, which may affect their ability to express pain. Given that sensitivity to noxious stimuli in adolescents with ASD has not been systematically assessed, here we measured warm and cool detection thresholds and heat and cold pain thresholds in 20 high-functioning adolescents with ASD and 55 typically developing adolescents using a method-of-limits quantitative sensory testing protocol. Adolescents with ASD had a loss of sensory function for thermal detection (P < .001, both warm and cool detection thresholds) but not pain threshold (P > .05, both heat and cold pain thresholds) in comparison to controls, with no evidence for significant age or sex effects (P > .05). Intelligence quotients and symptomatology were significantly correlated with a loss of some types of thermal perception in the ASD population (ie, warm detection threshold, cool detection threshold, and heat pain threshold; P < .05). Decreased thermal sensitivity in adolescents with ASD may be associated with cognitive impairments relating to attentional deficits. Our findings are consistent with previous literature indicating an association between thermal perception and cortical thickness in brain regions involved in somatosensation, cognition, and salience detection. Further brain-imaging research is needed to determine the neural mechanisms underlying thermal perceptual deficits in adolescents with ASD. PERSPECTIVE: We report quantitative evidence for altered thermal thresholds in adolescents with ASD. Reduced sensitivity to warmth, coolness, and heat pain was related to impaired cognitive ability. Caregivers and clinicians should consider cognitive ability when assessing and managing pain in adolescents with ASD.

Assessing pain intensity in children with chronic pain: convergent and discriminant validity of the 0 to 10 numerical rating scale in clinical practice.

BACKGROUND: In clinical practice, children are often asked to rate their pain intensity on a simple 0 to 10 numerical rating scale (NRS). Although the NRS is a well-established measure for adults, no study has yet evaluated its validity for children with chronic pain. OBJECTIVES: To examine the convergent and discriminant validity of the NRS as it is used within regular clinical practice to document pain intensity for children with chronic pain. Interchangeability between the NRS and an analogue pain measure was also assessed. METHODS: A cohort of 143 children (mean [± SD] age 14.1±2.4 years; 72% female) rated their pain intensity (current, usual, lowest and strongest levels) on a verbally administered 0 to 10 NRS during their first appointment at a specialized pain clinic. In a separate session that occurred either immediately before or after their appointment, children also rated their pain using the validated 0 to 10 coloured analogue scale (CAS). RESULTS: NRS ratings met a priori criteria for convergent validity (r>0.3 to 0.5), correlating with CAS ratings at all four pain levels (r=0.58 to 0.68; all P<0.001). NRS for usual pain intensity differed significantly from an affective pain rating, as hypothesized (Z=2.84; P=0.005), demonstrating discriminant validity. The absolute differences between NRS and CAS pain scores were small (range 0.98±1.4 to 1.75±1.9); however, the two scales were not interchangeable. CONCLUSIONS: The present study provides preliminary evidence that the NRS is a valid measure for assessing pain intensity in children with chronic pain.

Thermal pain and sensory processing in children with sickle cell disease.

OBJECTIVES: Early tissue injury and recurrent pain in sickle cell disease (SCD) may alter pain and sensory processing. In this study, we evaluate thermal pain and sensory processing for 27 children aged 10.3 to 18.3 years with SCD and 28 African-American control patients. MATERIALS AND METHODS: Outcome measures included heat and cold detection thresholds, heat and cold pain thresholds, and thermal perceptual sensitization at the volar surface of the dominant forearm and thenar eminence of the nondominant hand. RESULTS: Children with SCD were less sensitive to heat detection (P=0.006) and cold detection (P=0.015) stimuli at the thenar eminence compared with controls. At the forearm, no difference was found between groups for cold (P=0.58) or heat (P=0.07) detection thresholds. Children with SCD had increased sensitivity to cold pain at the forearm (P=0.03) compared with controls, but not when measured at the thenar eminence (P=0.084). There was no evidence that children with SCD had altered heat pain thresholds compared with controls. There was no difference between groups for perceptual sensitization at the thenar eminence (41% vs. 39%) (χ=0.15, P>0.1) or at the forearm (30% vs. 36%) (χ=0.23, P>0.5). DISCUSSION: Three of ten quantitative sensory tests were found to differ between groups. These results suggest that SCD may influence pain and sensory processing in children, but our interpretation is necessarily cautious. Due to the small differences in measures found between groups, further investigation is required to confirm our findings. If confirmed, the development of population-specific reference standards for quantitative sensory testing may emerge as a useful clinical tool for pain physicians in identifying and quantifying pain and sensory processing in children with SCD.

Risk factors associated with self-injurious behaviors in children and adolescents with autism spectrum disorders.

While self-injurious behaviors (SIB) can cause significant morbidity for children with autism spectrum disorders (ASD), little is known about its associated risk factors. We assessed 7 factors that may influence self-injury in a large cohort of children with ASD: (a) atypical sensory processing; (b) impaired cognitive ability; (c) abnormal functional communication; (d) abnormal social functioning; (e) age; (f) the need for sameness; (g) rituals and compulsions. Half (52.3%, n = 126) of the children (n = 241, aged 2-19 years) demonstrated SIB. Abnormal sensory processing was the strongest single predictor of self-injury followed by sameness, impaired cognitive ability and social functioning. Since atypical sensory processing and sameness have a greater relative impact on SIB, treatment approaches that focus on these factors may be beneficial in reducing self-harm in children with ASD.

Clinical impact and evidence base for physiotherapy in treating childhood chronic pain.

PURPOSE: As part of the special series on pain, our objectives are to describe the key features of chronic pain in children, present the rationale for interdisciplinary treatment, report a case study based on our biopsychosocial approach, and highlight the integral role of physiotherapy in reducing children's pain and improving function. We also evaluate the evidence base supporting physiotherapy for treating chronic neuropathic pain in children. SUMMARY OF KEY POINTS: Chronic pain affects many children and adolescents. Certain challenging pain conditions begin primarily during adolescence and disproportionately affect girls and women. Children with these conditions require an interdisciplinary treatment programme that includes physiotherapy as well as medication and/or psychological intervention. Converging lines of evidence from cohort follow-up studies, retrospective chart reviews, and one randomized controlled trial support the effectiveness of physiotherapy within an interdisciplinary programme for treating children with chronic pain. CONCLUSIONS: Evidence-based practice dictates that health care providers adopt clear guidelines for determining when treatments are effective and for identifying children for whom such treatments are most effective. Thus, additional well-designed trials are required to better identify the specific physiotherapy modalities that are most important in improving children's pain and function.

Reducing distress for children during invasive procedures: randomized clinical trial of effectiveness of the PediSedate.

BACKGROUND: Procedural pain control remains problematic for young children, especially during anxiety-causing procedures for which children should not be deeply sedated. The PediSedate was designed to address this problem by delivering nitrous oxide in oxygen through a simple nosepiece, combined with an interactive video component, so that children can use attention and distraction with drug delivery. OBJECTIVES: We conducted a randomized clinical trial to evaluate the effectiveness of the PediSedate for reducing children's behavioral distress in comparison with standard care in the emergency department. Secondary objectives were to assess children's acceptance, cooperation, and pain. METHODS: Thirty-six children, aged 3-9 years old, who required invasive procedures associated with high levels of anxiety and low levels of pain such as sutures, IVs, and lumbar punctures were randomized to receive either the standard care or the PediSedate. The primary outcome was children's distress (observational scale of behavioral distress) that was monitored before and during the procedure. RESULTS: Children randomized to the PediSedate group had significantly less distress during invasive procedures (mean = 1.8, sd = 3.2) than children receiving standard care (mean = 9.3, SD = 5.6; anova, P < 0.0001). Also, children in the PediSedate group were more cooperative [chi(2)(1) = 22.05, P < 0.0001] and fewer children reported pain [chi(2)(1) = 14.45, P < 0.001]. CONCLUSIONS: Previous studies have demonstrated the effectiveness of nitrous oxide sedation alone for minimizing pain and distress during invasive procedures. We have found that delivering nitrous oxide sedation via a system combined with an interactive video component is also effective. Further studies should determine which factors are dominant and determine the specific failure rate for this delivery system in comparison with other systems.

The complex minds of teenagers: neuroanatomy of personality differs between sexes.

Extraversion and neuroticism influence behaviour and mood. Extreme expressions of these personality traits may predispose individuals to developing chronic functional pains and mood disorders that predominantly affect women. We acquired anatomical MRI scans and personality scores from healthy male and female adolescents and measured gray matter volume (GMV) and cortical thickness to test the hypothesis that neuroticism and extraversion contribute to sex differences in fronto-limbic cortical development during a crucial period of social and biological maturation. In females, extraversion correlated negatively with medial frontal gyrus GMV and neuroticism correlated positively with subgenual anterior cingulate cortex GMV and cortical thickness. Interestingly, correlations between GMV and personality in males showed an opposite effect. Given the association of these cortical areas with social cognition and emotional processing, we suggest that a neuro-maturational divergence during adolescence accounts for the higher prevalence of specific chronic pains and mood disorders in females.

Anxiety sensitivity, fear of pain and pain-related disability in children and adolescents with chronic pain.

BACKGROUND: Converging lines of evidence suggest that anxiety sensitivity and fear of pain may be important vulnerability factors in the development of avoidance behaviours and disability in adults with chronic pain. However, these factors have not been evaluated in children with chronic pain. OBJECTIVES: To examine the relationships among anxiety sensitivity, fear of pain and pain-related disability in children and adolescents with chronic pain. METHODS: An interview and five questionnaires (Childhood Anxiety Sensitivity Index, Pain Anxiety Symptoms Scale, Functional Disability Inventory, Multidimensional Anxiety Scale for Children, and Reynolds Child or Adolescent Depression Scale) were administered to 21 children and adolescents eight to 17 years of age (mean +/- SD 14.24+/-2.21 years) who continued to experience pain an average of three years after discharge from a specialized pain clinic for children. RESULTS: Anxiety sensitivity accounted for 38.6% of the variance in fear of pain (F[1,20]=11.30; P=0.003) and fear of pain accounted for 39.9% of the variance in pain-related disability (F[1,20]=11.95; P=0.003), but anxiety sensitivity was not significantly related to pain disability (R2=0.09; P>0.05). CONCLUSIONS: These findings indicate that children with high levels of anxiety sensitivity had a higher fear of pain, which, in turn, was linked to increased pain disability. The results of this study suggest that anxiety sensitivity and fear of pain may play important and distinct roles in the processes that maintain chronic pain and pain-related disability in children.

Children with chronic pain: impact of sex and age on long-term outcomes.

The present study examined the long-term pain and disability outcomes of a pediatric chronic pain clinic cohort and evaluated whether these outcomes differed by age and sex. Patients were interviewed a mean of 3 years after their last appointment at a pediatric pain clinic. The cohort comprised 95 females and 48 males, aged 5-23 years when interviewed. Of the cohort, 62.2% (67 females, 22 males) reported continuing pain. Females were significantly more likely than males to report continuing pain (OR=2.9, 95% CI=1.4-5.8, p=.005), use of health care (OR=5.1, 95% CI=1.4-18.5, p=.01), medication (OR=4.7, 95% CI=1.3-16.9, p=.02) and non-drug methods of pain control (OR=3.4, 95% CI=1.3-9.2, p=.02). For patients whose pain had associated psychosocial factors, females (76.4%) were significantly more likely than males (21.4%) to report continuing pain (OR=13.8, 95% CI=3.3-58.4, p=.005). Finally, among patients still experiencing pain, the frequency of pain episodes increased significantly with age (OR=1.3, 95% CI=1.0-1.5, p=.02). Results indicate that chronic pain persists for many children despite treatment at specialized clinics. Females may be at higher risk for continuing pain and report greater use of health care, medication, and non-drug methods of pain control.

Pain prevalence in nine- to 13-year-old schoolchildren.

BACKGROUND: Despite significant progress in the epidemiology of chronic pain in adults, major gaps remain in our understanding of the epidemiology of chronic pain in children. In particular, the incidence, prevalence and sensory characteristics of many types of pain in Canadian children are unknown. OBJECTIVES: A study to obtain the lifetime and point prevalence of common acute pains, recurrent pain syndromes and chronic pains was conducted in a cohort of 495 school children, nine to 13 years of age, in eastern Ontario. METHODS: Children reported their pain experiences and described the intensity, affect and duration of the pains experienced over the previous month by completing the Pain Experience Interview -- Short Form. RESULTS: The majority of children (96%) experienced some acute pain over the previous month, with headache (78%) being most frequently reported. Lifetime prevalence for certain acute pains differed significantly by sex (P<0.05). Fifty-seven per cent of children reported experiencing at least one recurrent pain, while 6% were identified as having had or currently having chronic pain. DISCUSSION: The prevalence of acute pain in this Canadian cohort is consistent with international estimates of acute pain experiences (ie, headache) and recurrent pain problems (ie, recurring headache, abdominal pain and growing pains). However, 6% of children reported chronic pain. The self-completed Pain Experience Interview--Short Form provides a feasible administration technique for obtaining population estimates of childhood pain, and for conducting longitudinal studies to identify risk and prognostic factors for chronic pain.

A survey of children's acute, recurrent, and chronic pain: validation of the pain experience interview.

The ultimate objective of our epidemiological research is to complete a longitudinal population-based study to document the prevalence and impact of acute, recurrent, and chronic pain in children and adolescents. As the first phase of our epidemiological research, we developed a comprehensive screening instrument for identifying children with acute, recurrent, and chronic pain, the Pain Experience Interview. We designed this interview to provide information about the lifetime and point prevalence of various pains, and also to provide information about the intensity, affect, duration, and frequency of children's pain. The primary objective of this study was to validate the Pain Experience Interview using the discriminant validation procedure of group differences. The secondary objectives of our study were to obtain descriptive data on children's acute, recurrent, and chronic pain experiences and to conduct exploratory analyses on age- and gender-related differences in children's pain experiences. We interviewed 187 children from five different health groups (arthritis, cancer, enuresis, recurrent headaches, and healthy) to provide distinct subsets of children with respect to their acute, recurrent, and chronic pain experience, and from four different age groups (5-7, 8-10, 11-13, and 14-16 years) to provide distinct subgroups with respect to children's developmental level. To test the interview we determined a priori several study predictions about children's pain experiences. These included four predictions about the common response patterns that we would expect to observe for all children based on our understanding of acute pain caused by trauma/disease, and six predictions about the distinct response patterns that we would expect to observe based on the known differences among children in their experiences of headache, acute treatment-related pain, recurrent pain, and chronic pain. All study predictions were confirmed, demonstrating that the Pain Experience Interview is a valid screening instrument for differentiating children with different types of pain problems. The interview can provide estimates for the lifetime and point prevalence of various pains in children, and data on the intensity, affect, duration, and frequency of their pain experiences.

A new analogue scale for assessing children's pain: an initial validation study.

A new instrument was designed to provide a practical clinical measure for assessing children's pain intensity and pain affect. The pocket size measure includes a Coloured Analogue Scale (CAS) to assess intensity and a facial affective scale to assess the aversive component of pain. Both scales have numerical ratings on the back, so that the person administering it can quickly note the numbers that represent a child's pain. This study was conducted to determine the validity of the new instrument by evaluating the psychophysical properties of the intensity scale and by evaluating the discriminant validity of the intensity and affective scales. Since visual analogue scales (VAS) are valid and reliable measures for assessing children's pain, children's ability to use the new analog scale was compared with their performance on a VAS. Children's ability to rate pain affect using an affective scale, in which the 9 faces on a Facial Affective Scale (FAS) are presented in an ordered sequence from least to most distressed, was compared to their performance on the original FAS, in which the same faces were presented in a random order. Using a parallel groups design, 104 children (5-16 years; 60 female, 44 male; 51 healthy and 53 with recurrent headaches) were randomized into two groups: CAS or VAS. Children used the assigned scale to complete a calibration task, in which they rated the sizes of 7 circles varying in area (491, 804, 1385, 2923, 3848, 5675 and 7854 mm2). The psychophysical function relating perceived circle size to actual physical size was determined for the CAS and VAS. Children's CAS and VAS responses on the calibration task yielded similar mathematical relationships: psi cas = 0.035I0.87, psi vas = 0.027I0.89, where psi = perceived magnitude and I = stimulus intensity. The R2 values were 0.921 and 0.922 for the CAS and VAS groups, respectively. Analyses of covariance revealed no significant differences in the characteristics of these relationships, i.e., R2, slope, or y intercept, by scale type. Children used the same scale to complete the Children's Pain Inventory (CPI), in which they rated the intensity and affect of 16 painful events (varying in nature and extent of tissue damage). Children's CAS and VAS responses on the CPI were similar. Analyses of covariance indicated that there were no differences in either intensity or affective ratings by scale type. However, the mean number of painful events experienced by children increased significantly with age (P = 0.0001). Intensity ratings decreased significantly with age (P = 0.002), but affective ratings did not vary with age. The new instrument has equivalent psychometric properties to a 165 mm VAS. However, the CAS was rated as easier to administer and score than the VAS, so it may be more practical for routine clinical use. Since the CAS has fulfilled the first two criteria for a pain measure (psychophysical properties and discriminant validity), it is ethical to proceed with the formal definitive test for construct validity, in which children from various clinical populations use the CAS scale to assess their own pain.

The validation of visual analogue scales as ratio scale measures for chronic and experimental pain.

Visual analogue scales (VAS) of sensory intensity and affective magnitude were validated as ratio scale measures for both chronic and experimental pain. Chronic pain patients and healthy volunteers made VAS sensory and affective responses to 6 noxious thermal stimuli (43, 45, 47, 48, 49 and 51 degrees C) applied for 5 sec to the forearm by a contact thermode. Sensory VAS and affective VAS responses to these temperatures yielded power functions with exponents 2.1 and 3.8, respectively; these functions were similar for pain patients and for volunteers. The power functions were predictive of estimated ratios of sensation or affect produced by pairs of standard temperatures (e.g. 47 and 49 degrees C), thereby providing direct evidence for ratio scaling properties of VAS. Vas sensory intensity responses to experimental pain, VAS sensory intensity responses to different levels of chronic pain, and direct temperature (experimental pain) matches to 3 levels of chronic pain were all internally consistent, thereby demonstrating the valid use of VAS for the measurement of and comparison between chronic pain and experimental heat pain.

Masseter inhibitory periods and sensations evoked by electrical tooth pulp stimulation.

The masseter inhibitory period and sensations evoked by electrical tooth pulp stimulation were assessed in 30 human subjects. Five intensities of electrical stimuli, producing sensations varying from below sensory detection threshold to suprathreshold pain, were applied to upper central incisors. At each stimulus intensity a train of 30, 1-msec, cathodal pulses with an interpulse interval of 2 sec was applied. The averaged masseter activity evoked by the 30 pulses at a fixed stimulus intensity was compared to the quality of the sensation elicited. The threshold for the masseter inhibitory period coincided approximately with an individual's detection threshold for the tooth pulp stimulation. Three configurations of masseter inhibitory periods (single, double and merged) were produced by different stimulus intensities. However, no particular configuration was associated unequivocally with pain sensation. Increases in stimulus intensity evoked changes both in the configuration of the masseter inhibitory period and in the quality of the sensation produced. Chi square analyses showed significant, but progressively weaker, associations between: (1) masseter inhibitory period configuration and stimulus intensity; (2) quality of sensation and stimulus intensity; and (3) quality of sensation and masseter inhibitory period configuration. The weakness of the association between the quality of sensation and masseter inhibitory period configuration also was demonstrated in a double-blind study of the effects of a narcotic analgesic, fentanyl. Although the strengths of non-pain and pain sensations were reduced significantly after fentanyl, there were no changes in the masseter inhibitory periods.

A validation model for verbal description scaling of human clinical pain.

Twenty-nine subjects used quantified verbal descriptors of sensory intensity (i.e., weak, mild, intense) or unpleasantness (i.e., annoying, unpleasant, distressing) to assess the intensity or unpleasantness of sensations evoked by painful electrical stimulation of the tooth pulp over a broad stimulus range, and by a natural thermal tooth pulp stimulus, cold spray applied to exposed dentin. In addition, subjects matched the intensity or unpleasantness of the sensations evoked by the natural stimulus to that of the electrical stimuli by both the Method of Limits and the Method of Constant Stimuli. Quantified verbal descriptor values of either the sensory intensity or unpleasantness of the electrical stimuli were linearly related to stimulus intensity on a log scale, indicating that the relationships can be described by power functions. The quantified verbal description of the natural thermal stimulus and the intensity of the electrical stimulus directly matched to the thermal stimulus determined the coordinates of the clinical stimulus data point. This point was close to the experimental stimulus power function, indicating that the verbal magnitude of the clinical stimulus is predicted by the verbal magnitude of the specific electrical stimulus intensity that was matched to the clinical stimulus. This consistency supports the validity of the use of quantified verbal descriptors for the assessment of both experimentally controlled noxious stimulation and uncontrolled clinical pain sensations. It also supports the validity of direct matches between clinical and experimental pain sensations and the unpleasantness of these sensations. This procedure provides a useful independent validational paradigm for clinical pain assessment.