Abstract
Chronic pain is a significant yet underreported problem in the pediatric population. Children suffering from chronic pain experience psychological, emotional, and social repercussions. The potential for such consequences to negatively impact a child’s life has fostered the development of a multidisciplinary approach to treat chronic pain that includes variety of behavioral, pharmacological, and physical therapies. Focus is made on the child’s physical and psychological well being. Advances in functional imaging research may guide further treatment strategies in approaching pediatric pain.
Keywords
anesthesiology, chronic pain, comlementary medicine, functional imaging, interdisciplinary, pediatric
Chronic pain is a significant yet underreported problem in the pediatric population that carries psychological, emotional, and social repercussions for both the child and family. The potential for such consequences to negatively impact a child’s quality of life has fostered the development of a multidisciplinary approach to treat pediatric pain. A variety of behavioral, pharmacological, and physical therapies are used in pediatric chronic pain treatment regimens. Interventional procedures may be introduced after patients fail other treatment approaches.
Chronic pain in childhood and adolescence is more common than is reported and prevalence rates vary substantially between data from different studies. Children experiencing persistent or recurrent chronic pain may miss school or withdraw from social activities and are at risk of developing internalizing symptoms in response to their pain. Given these consequences, researchers and clinicians are working to develop effective interdisciplinary strategies to manage chronic pain in children and adolescents.
Assessment of Chronic Pain in Children
Assessment of children with chronic pain requires a biopsychosocial perspective that accounts for the biologic, developmental, temperamental, cognitive-behavioral, affective, social, and situational factors that shape the child’s pain experience. Each domain may become a target of assessment and intervention. Several developmentally sensitive validated instruments are now available to measure the varied aspects of a child’s pain ( Table 37.1 ).
| Pain Measures | Disability or Quality of Life Assessment Tools | Other Behavioral Measures |
|---|---|---|
| Varni-Thompson Pediatric Pain Questionnaire (Ages 5–18 years) | Functional Disability Inventory (Ages 8–17 years) | Children’s Somatization Inventory (Ages 8–18 years) |
| Children’s Comprehensive Pain Questionnaire (Ages 5–19 years) | Child Health Questionnaire (Ages 5+) | Harter Scales of Perceived Competence for Children (Ages 4–12) |
| Pain Behavior Observation Method (Ages 6–17) | Children’s Activity Limitations Scale (Ages 8–16 years) | – |
| Pain Diary (Ages 8+) | – | – |
The Children’s Comprehensive Pain Questionnaire (CCPQ) and the Varni-Thompson Pediatric Pain Questionnaire (VTPPQ) are age-specific standardized interviews for school-age and adolescent children and their parents that provide comprehensive evaluations of a child’s chronic pain. Both interviews separately assess the child’s and parents’ experience with a pain-related problem by utilizing open-ended questions, checklists, and quantitative pain-rating scales. Some studies suggest potential limitations to these self-report measures because of cultural or cognitive differences among families. The Pain Behavior Observation Method is a 10-minute observational pain behavior measure that can be used in children who may have difficulty with self-report measures because of age-related or cognitive limitations. Electronic diary assessment of pain and disability has gained popularity in recent years, and studies have supported their use in children with chronic pain, demonstrating increased compliance and accuracy in diary recording when compared to traditional paper diaries.
The ability to function in tasks of daily living is a critical outcome measure to assess when treating children and adolescents with chronic pain. In some cases, pain cannot be completely relieved and the child must learn to cope with and adapt to the pain to participate in normal developmental activities and tasks, such as attending school, participating in extracurricular activities, and maintaining social relationships. Various measures have been developed to assess the child’s functional ability. The Functional Disability Inventory (FDI) was developed to assess illness-related disability in children and adolescents. It is particularly useful for children with pain disorders that are associated with psychological factors and pain-associated disability. The Child Health Questionnaire may be used to assess general quality of life in children with chronic pain and has the advantage that the scores obtained can be compared with standardized samples of scores obtained by children with other medical illnesses. The Child Activity Limitations Interview (CALI) measures the impact of recurrent pain on the child’s daily activities to identify appropriate targets for treatment.
Other instruments used to evaluate psychological factors that are contributing to a child’s behavioral adaptation to chronic pain include the Children’s Somatization Inventory (CSI), which measures a child’s propensity towards somatization, and the Harter Scales of Perceived Competence, which assesses a child’s judgment about his or her capabilities in functional domains such as school performance, peer relationships, and athletic abilities. The Patient Reported Outcomes Measurement Information System (PROMIS) is a relatively new tool that is gaining popularity for tracking physical, mental, and social well-being in children with chronic pain.
Interdisciplinary Approach to Pediatric Chronic Pain Management
The introduction of interdisciplinary chronic pain management programs has allowed children to be evaluated and treated by a number of consultants during a single office visit. Many pediatric pain clinics are composed of an anesthesiologist specialized in pain management, a child psychologist with a special interest in pain, physical therapists, and complementary medicine specialists who incorporate massage therapy, acupuncture therapy, as well as biofeedback. This comprehensive approach enables patients to receive better care with minimal disruption to their lives.
Psychological pain management methods aim to improve the child and family’s understanding of the child’s pain and its treatment by focusing on factors that may reduce or exacerbate symptoms. The child’s cognitive and behavioral coping skills are fostered in an effort to reduce pain-related discomfort and disability. Eccleston and colleagues performed a meta-analysis to evaluate the efficacy of behavioral interventions for treating pediatric chronic pain. They concluded that strong evidence exists to support psychological treatments, specifically relaxation and cognitive behavioral therapy, as effective methods to reduce the severity and frequency of chronic pain in children and adolescents. Other studies have suggested that interdisciplinary pediatric pain rehabilitation may facilitate increased willingness to self-manage pain, which is associated with improvements in function and psychological well-being.
Physical therapy is geared toward reestablishing adequate functional ability of the child. In children, physical therapy is especially useful in cases of myofascial pain and can be implemented at a rehabilitation facility, home, or school. In younger children, these exercises can take the form of play that is geared toward improving musculoskeletal function, fine and gross motor function, posture, endurance, and circulation. Restoring the patient’s physical ability can help the child participate in activities of daily living and improve overall function.
Complementary and alternative medicine (CAM) is defined by the National Center for CAM as “a group of diverse medical and health care systems, practices, and products that are not generally considered to be part of conventional medicine.” Biofeedback, hypnosis, guided-imagery, mindfulness, massage, and acupuncture have been used as adjunctive treatments for chronic, acute, and recurrent pain in both pediatric and adult populations. Gut-directed hypnotherapy for functional abdominal pain (FAP) and irritable bowel syndrome appears to be superior to traditional medical management of such conditions. Although limited data are available to support the efficacy of CAM in pediatric patients, such treatments offer the potential for pain relief with a relatively low incidence of side effects.
Many tertiary pain centers in the United States have adopted a multidisciplinary approach to pain management that incorporates use of at least a subset of CAM modalities. In a 2005 survey of 43 pediatric anesthesiology fellowship programs, 38 reported that their clinical services to patients included at least one CAM modality, including biofeedback (65%), guided imagery (49%), relaxation therapy (33%), massage (35%), hypnosis (44%), acupuncture (33%), art therapy (21%), and meditation (21%). Tsao et al. have suggested that the longer a child experiences pain, the more likely he or she is to express an interest in trying CAM treatment approaches.
Interventional procedures can serve as useful adjuncts to managing chronic pain conditions in children, especially in cases that are refractory to noninvasive treatments. This differs from the adult cohort for which such procedures are more commonly used as a diagnostic or therapeutic modality. The majority of literature on this topic consists of case reports and retrospective studies. Due to lack of scientific evidence, significant controversy surrounds the utility of invasive techniques for managing pediatric pain states.
Functional Imaging of Pediatric Chronic Pain States
The introduction of noninvasive neuroimaging techniques has significantly advanced our understanding of how chronic pain affects the structure and function of cortical, subcortical, and brainstem networks. Brain imaging studies of chronic pain in pediatric populations offer unique opportunities to understand changes in the young brain from both developmental and neuroplastic perspectives. In the pediatric population, the brain undergoes rapid changes and may be more likely to recover after an injury. Very few studies have addressed the effects of pain on brain maturation and plasticity processes. The use of noninvasive imaging approaches to evaluate brain changes in pediatric patients may lead to novel treatment approaches, potentially limiting the development of long-term consequences.
Imaging techniques are being utilized in pain research to depict functional, biochemical, and anatomical changes within the brain ( Fig. 37.1 ). Below we provide a brief overview of these techniques and their relevance to the study of pediatric chronic pain states.
Functional Imaging Techniques
Functional magnetic resonance imaging (fMRI) determines cortical activation by measuring changes in the local concentration of paramagnetic deoxyhemoglobin. This technique, also referred to as blood oxygen level-dependent (BOLD) imaging, assesses regional neuronal activation by measuring changes in blood flow and blood volume, depicting dynamic changes with relatively high spatial resolution. Due to its noninvasive nature, fMRI can potentially be used repeatedly in children, allowing longitudinal studies on neural network development, disease process evolution, and treatment responses.
Lebel and colleagues have utilized fMRI to study cerebral activation patterns in pediatric patients with complex regional pain syndrome (CRPS). Children 9 to 18 years of age with lower extremity CRPS-I underwent two scanning sessions; the initial scan was performed during an active period of pain, and a follow-up scan was done after symptomatic recovery. Patients with active symptoms (including mechanical and thermal allodynia) demonstrated BOLD activation patterns that were similar to data reported in adults. Specifically, activation changes were noted in regions involved in pain processing (primary sensory-motor cotices, insula) as well as in areas that presumably contribute to the affective symptoms of pain (parietal, frontal, and temporal cortices). Brain activation patterns continued to differ between symptomatic patients and those who had recovered, suggesting that functional changes in central nervous system processing may outlast the signs and symptoms of CRPS.
Simons and colleagues applied fMRI to evaluate resting state functional connectivity of the amygdala with cortical and subcortical regions in a group of pediatric CRPS patients with age-sex matched control subjects before and after treatment. The investigators observed rapid changes in amygdala connectivity after patients underwent an aggressive physical-biobehavioral pain treatment program, serving as a potential indicator of treatment response. In addition, functional connectivity to several regions key to fear circuitry correlated with higher pain-related fear scores ( Fig. 37.2 ).
Cerebral near-infrared spectroscopy (NIRS), which detects subtle changes in the concentration of natural chromophores such as oxygenated and deoxygenated hemoglobin, has been successfully utilized in newborns, children, and adults to measure the hemodynamic and oxygenation changes related to cortical processing of specific stimuli. NIRS studies in neonates have noted that painful and tactile stimuli elicit specific hemodynamic responses in the somatosensory cortex, implying conscious sensory perception in preterm neonates.
Magnetic resonance spectroscopy (MRS) can be utilized to study alterations in neurotransmitters and neuronal markers. Several in vivo MRS techniques have been developed to provide unique information about brain chemistry. MRS has been used to gain insight into several conditions, including migraine, back pain, and spinal cord injury and has potential to provide biomarkers of disease that precede structural changes within the brain. No pediatric pain studies to date have utilized this imaging approach.
Diffusion Tensor Imaging (DTI) has been used to study a number of pain disorders, including migraine and poststroke centralized pain. This approach measures microstructural changes in water diffusion to determine changes in white matter tracts and when combined with fMRI studies, this approach may improve our understanding of functional anatomical mapping of brain activity.
Functional imaging of the brain changes that occur in pediatric chronic pain patients is an emerging field with great potential. Such techniques can serve as powerful noninvasive tools that may be used to perform longitudinal studies in children so we may better characterize the mechanisms of pain and ultimately improve therapeutic strategies.
Complex Regional Pain Syndrome
CRPS type I (CRPS-I) involves a group of symptoms involving extremity pain with neuropathic features, including allodynia and hyperalgesia, neurovascular degeneration, sudomotor dysfunction, trophic changes, and loss of motor function. Pediatric cases of CRPS-I typically begin in adolescence, and the lower extremity is more commonly affected than the upper extremity (ratio of approximately 5:1). Significant trauma is a much less frequent precipitating event than in adults. The majority of children involved appear to be Caucasian females. Studies in adult patients suggest that psychological factors are frequently involved in the CRPS-I pain experience. Contrary to this hypothesis, children with CRPS-I report no greater anxiety or depressive symptoms than children with other pain conditions. Pediatric CRPS-I patients do, however, demonstrate greater enmeshment with their parents and many exhibit a degree of overachievement.
Early recognition and management are the major factors in improving outcome and preventing symptom recurrence. Management should include an interdisciplinary approach. Although medication and procedure-based treatments may be performed in children, rehabilitative treatments thus far show the best evidence of yielding positive outcomes. Outcome reports from pediatric pain rehabilitation programs remain scarce in the literature and have primarily involved inpatient rehabilitative treatments, including hospitalization. Logan and colleagues recently reported disability reduction and improved physical and emotional functioning in pediatric CRPS-I patients who underwent an interdisciplinary day-hospital rehabilitation program.
Evaluation
A detailed history of the nature of the injury that includes the type and duration of pain, relieving and aggravating factors, and dependence on medications should be performed prior to physical examination. A thorough and systematic neurologic examination should be performed with evaluation of motor, sensory, cerebellar, cranial nerve, reflex, cognitive, and emotional functioning. A concerted effort should be made to rule out a rare, but possible, malignancy or central degenerative disorder. Allodynia is a common finding and hyperalgesia to cold is seen more frequently than sensitivity to heat. In children, the distribution is not generally restricted to particular dermatomes and commonly occurs along a glove-and-stocking distribution. Nerve conduction studies may provide insight into the nature of a nerve injury; however, the use of invasive electromyography may not be acceptable to children. Quantitative sensory testing (QST) in the affected limbs can be compared with data from normal healthy children. Although this involves cumbersome equipment, bedside QST may play a role in the diagnosis of CRPS-I in children and adolescents. Bone scans may be helpful in the diagnosis of CRPS-I. Although insufficient data exist to support their diagnostic accuracy in children, they can nevertheless be performed in children and adolescents with suspected CRPS-I.
Treatment
Management of CRPS-I can be frustrating for both the caregiver and the patient as no single therapy can uniformly provide relief of symptoms. Children, compared with adults, are thought to have a better response to noninvasive treatments. Therefore, treatments that have been reported effective in adults may not apply to pediatric patients. Despite this, most CRPS-I management techniques that are used in children have been extrapolated from the adult literature ( Fig. 37.3 ).
It is imperative to return the child to a functional state, including attendance at school. Behavioral measures are extremely useful in the management of CRPS-I in children and adolescents. For example, group therapy often helps family members cope with the situation. We generally advocate consultation with a medical psychologist during the initial visit to the pain clinic. Several techniques, including biofeedback, visual guided imagery, and structured counseling, have been shown to assist in the development of adequate coping skills. Participation in a day program for acute psychological intervention has been valuable for some of our patients, specifically those with significant psychiatric coillness.
Physical therapy is geared toward restoring adequate functional ability of the child. Transcutaneous electrical nerve stimulation (TENS) is widely used, and its efficacy has been studied in adults as well as children; therapeutic benefits with TENS in children with CRPS-I have been reported by Kesler and colleagues. We use TENS extensively in our practice, along with physical therapy, which consists of both active and passive physical modalities. The physical therapy program is geared toward individual patients, and the goal is to allow the child to participate in as many activities as possible. Other commonly used modalities include graded motor imagery, desensitization, warm and cold baths, massage therapy, and heat therapy. Such modalities, when used in conjunction with active physical modalities, can help ameliorate pain symptoms.
The following section focuses on therapeutic adjuncts used to treat pediatric CRPS-I, including pharmacotherapy, regional anesthesia, and sympathetic blockade. Most treatment approaches are extrapolated from efficacy data in adults.
Tricyclic Antidepressants
Despite the lack of adequately controlled studies in pediatric patients, tricyclic antidepressants (TCAs) are widely prescribed for several forms of neuropathic pain. Because amitriptyline may cause sedation and other anticholinergic side effects, nortriptyline is often used as an alternative in children. Thorough examination of the cardiovascular system is necessary before instituting TCA treatment because of the associated tachydysrhythmia and other conduction abnormalities of the heart, particularly prolonged QT syndrome.
Anticonvulsants
Anticonvulsant medications are commonly used to manage neuropathic pain in pediatric patients, especially since the introduction of gabapentin and pregabalin. Despite the lack of controlled trials in children to demonstrate the efficacy of either drug, both of these medications have been used in our practice with promising results. More controlled trials should be conducted to better determine the dosing and efficacy of this class of drugs in children with CRPS-I. An important side effect that we have noted in our clinic setting is the potential for increased somnolence, as well as the potential for weight gain in children taking pregabalin. This is important to consider, especially when treating adolescent girls who happen to be the majority of this cohort.
Selective Serotonin Reuptake Inhibitors and Serotonin-Norepinephrine Reuptake Inhibitors
Despite the lack of proven efficacy of the use of selective serotonin reuptake inhibitors in the management of pain in children and adolescents, they are occasionally used to treat psychological comorbidity, including pain-associated depression. More recently, serotonin-norepinephrine reuptake inhibitors (e.g., duloxetine) have been introduced and used successfully to treat neuropathic pain, especially in patients with psychological comorbidity.
Systemic Vasodilators
Several patients with CRPS-I have benefited from the use of vasodilators such as prazosin, nifedipine, and phenoxybenzamine. However, overwhelming adverse effects of orthostatic hypotension often offset the efficacy of this therapy.
Regional Anesthesia and Sympathetic Blocks
A common treatment of these syndromes is to interrupt the apparent pathologic reflexes by performing sympathetic blocks. Regional anesthesia, which is often utilized in adults for the diagnosis and management of CRPS-I, is generally introduced in children after pharmacological and cognitive-behavioral management have been exhausted. In severe cases, regional anesthesia is used to introduce a physical therapy regimen.
Central neuraxial blockade may be performed in children with severe pain to facilitate the introduction of physical therapy. Intrathecal analgesia has been reported to be an effective method for treating refractory CRPS-I in children. Bier block has been used for mild to moderate cases of CRPS-I as a primary modality for providing analgesia and sympathetic blockade. Although various substances have been used to provide a Bier block, a local anesthetic in combination with either an α2-agonist or an NSAID appears to produce better results.
Peripheral nerve blocks can be used to facilitate physical therapy while providing a sympathectomy. Serial peripheral nerve blocks are often performed, after which the patient’s pain relief may outlast the duration of conduction blockade. Continuous peripheral nerve blocks (CPNBs) have been reported to be effective in both controlling pain and facilitating physical therapy in children with CRPS ( Fig. 37.4 ). Despite such reports, limited data exist regarding the feasibility, safety, and efficacy of CPNBs for the treatment of CRPS-I in children.
