Chapter 42
Pain in individuals with intellectual disabilities

Abagail Raiter¹, Alyssa Merbler², Chantel C. Burkitt^1,3, Frank J. Symons³, & Tim F. Oberlander^4,5

¹ Gillette Children’s Specialty Healthcare, St. Paul, Minnesota, USA

² Department of Educational Psychology, University of Minnesota, Minneapolis, Minnesota, USA

³ Special Education Program, Department of Educational Psychology, University of Minnesota, Minneapolis, Minnesota, USA

⁴ Department of Pediatrics, School of Population and Public Health, Faculty of Medicine, University of British Columbia, University of British Columbia, Vancouver, British Columbia, Canada

⁵ Complex Pain Service, British Columbia Children’s Hospital, Vancouver, British Columbia, Canada

Introduction & Overview

Expression of pain by individuals with intellectual and related developmental disabilities (e.g. cerebral palsy) and disorders (e.g. autism) is frequently ambiguous and its recognition by caregivers and health care providers can be highly subjective. The potential for ambiguity and subjectivity presents a tremendous challenge for clinicians, researchers, individuals with disabilities and their families. Even when pain‐specific behaviors are present, such behaviors may be regarded as altered, blunted or confused with other sources of generalized stress, arousal or, in the extreme, misinterpreted as a manifestation of a behavior disorder of psychological origin. There is no reason, however, to believe that pain is any less frequent in the lives of someone with an intellectual or related developmental disability that alters the way they communicate or that such an individual would be insensitive or indifferent to pain.

Until the early 2000s, pain in people with intellectual disability (ID) received little scientific attention and as study participants, individuals with ID have been historically and systematically excluded from pain and related research. This is starting to change [1]. The International Association for the Study of Pain (IASP) updated their definition of pain in 2020 to “an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage” [2]. The IASP definition is accompanied by a critical note stating that “verbal description is only one of several behaviors to express pain; inability to communicate does not negate the possibility that a human or a nonhuman animal experiences pain” [2]. In this sense, our task is to recognize that all features of an individual’s behavioral and physiologic repertoire may function as legitimate indices of pain expression and experience and develop strategies to manage this universal, but highly individual, human condition.

The purpose of this chapter is to provide an overview of several issues inherent to assessing and managing pain among children and adults with intellectual and developmental disabilities (IDD). Wherever possible, our focus is specific to intellectual disability as distinct from but related to the concept of developmental disability (e.g. cerebral palsy is a developmental disability in which some children also have intellectual disability, but some do not). It is beyond the scope of the chapter to provide an exhaustive review, for more information, readers are directed to Oberlander and Symons [3], Siden and Oberlander [4], Doody and Baily [5] or Barney et al. [1]. The chapter begins by defining intellectual disability to clarify the clinical population and then briefly reviews the scope of the problem of pain among individuals with ID. Recent developments in assessment approaches are discussed and specific tools are described. Issues and approaches to pain management are then presented. Readers will note that the chapter and its citation pattern reflect the current reality of our knowledge in this area – much of the research addressing issues in pain and ID has focused on the scope of the problem and assessment in pediatric populations with very little work specific to management [1].

Defining ID and Conceptual Issues

The American Association on Intellectual and Developmental Disabilities (AAIDD) currently defines ID as a disability with onset by 18 years of age characterized by significant limitations in both intellectual functioning and in adaptive behavior, which may cover many everyday social and practical skills [6]. Adaptive behavior can include tasks such as literacy, social problem solving, safety or occupational skills. Evidence of these limitations must be evident before adulthood. AAIDD emphasizes the assessment of ID must include all available information, including considering the cultural, linguistic and community contexts of the individual [6].

Regardless of the degree of ID and the underlying neurological condition, functional limitations frequently confound the presentation of pain in individuals with intellectual and developmental disabilities [7]. Given that the most common approach to pain assessment is based on self‐report, how can pain be assessed and managed when the typical means of verbal or nonverbal communication or cognition is altered or absent? In the absence of easily recognized verbal or motor‐dependent forms of communication, it remains uncertain if the pain experience itself is different or whether only the expressive manifestations are altered. Indeed, without easily recognizable means of communication or functional motor skills, pain may remain under recognized and under treated. Despite the potential for altered nociception and pain expression, there is no evidence that cognitively or motor impaired individuals are spared any of the miseries of a noxious experience [8].

Scope of the Problem of Pain in Individuals with ID

Epidemiology

There is a limited but emerging database regarding the epidemiology of pain among children and adults with ID, with varying levels of pain reported across studies [9]. Hauer et al. [10] reported pain occurring weekly in 44% of children with moderate to profound cognitive impairment and almost daily in 41‐42% of children with severe cognitive impairment. Breau et al. [11] documented 78% of children with moderate to profound ID (N=94) experienced some type of pain over a four‐week period, with 62% experiencing nonaccidental pain, as reported by caregivers. Each week, 35‐52% of participants had pain. The mean duration was more than nine hours per week and nonaccidental pain had a mean rating of six out of ten. Those with more severe limitations reported more nonaccidental pain. Similarly, Stallard and colleagues [12], reported 74% of their sample of children with ID (N=34) experienced some form of pain over a two‐week period, with 68% having pain rated as moderate to severe. Most troubling was that none of the children were reported to be receiving any type of pain management.

Some studies of adults with ID have produced similar prevalence estimates. An early investigation of chronic pain in adults with ID and cerebral palsy found 67% of their sample reported pain lasting more than 3 months. Many of the pain types listed had a mean duration of greater than 10 years, with a report of up to 20 years in one case, and 56% of individuals reported they had daily pain [13]. More recently, a secondary analysis of health interviews of individuals with ID found that 67% of participants reported living with pain [14]. Other studies have reported lower chronic pain prevalence estimates including 13% and 15% of adults with ID [15, 16]. Overall, there is a wide range of pain prevalence estimates with the upper bound tending to be in the 60‐70% range suggesting the need for more routine and systematic assessment and treatment considerations.

Pain Sources and Risk Factors

Whether from a single or multifactorial cause (e.g. genetic/metabolic disorders, multi‐organ syndromes, traumatic brain injury or disorders of unknown origin), ID can be associated with multiple sources of acute and chronic pain. It can present as acute or chronic and be from internal or external sources. Adults with ID often have multiple medical conditions [17], many of which can result in pain or are associated with chronic pain (e.g. fractures, dental problems, arthritis). Activities of daily living may involve the use of assistive devices for positioning and mobility (e.g. walkers, seating systems, manual and power wheelchairs), which can cause discomfort and/or pain [18]. Dislocated hips, pressure sores from skin breakdown and repetitive use injuries occur and must be considered. Splinting and casting may be required for the prevention and treatment of contractures and can be associated with pain. For some, eating and swallowing are difficult and special feeding techniques or enterostomy feeds are required. Feeding tubes can result in gastric distention, tugging or pulling of the tube or skin breakdown at the tube site are a potential cause of pain on an everyday basis. Constipation should also be considered a common source of discomfort.

Motor impairments, such as those in cerebral palsy, may be characterized by increased tone, spasms, increased deep tendon reflexes and clonus, coupled with weakness and loss of dexterity. Spasticity and spasms can cause significant discomfort through waking and sleeping hours [19]. Treatment of spasticity frequently involves invasive procedures. High tone/spasticity may be treated through surgical intervention (selective dorsal rhizotomy) or by surgical implantation of an intrathecal baclofen pump, while pharmacologic management of tone may include intramuscular injection of botulinum toxin A [19.20]. Non‐invasive therapies can also contribute heavily to frequent pain; adult patients with cerebral palsy report that their memories of pain in childhood center around regular physical therapy sessions and stretching [21].

Although the nociceptive pain of surgery may seem obvious, there are times when repeated surgery or direct trauma to a nerve results in long lasting neuropathic pain [22]. Neuropathic pain can be difficult to identify and treat but should be considered in individuals with severe neurological impairments (SNI) associated with ID with prolonged pain after an intervention. Another potential source of pain is central in origin (i.e., thalamic injury), where the pain afferents appear to be activated without an ongoing input either from tissue damage or peripheral nerve injury [22, 23]. The major evidence for central pain comes from the observation of pain behavior in children with advancing neurodegenerative diseases such as Krabbe disease, children with severe neurological impairments, adults with thalamic strokes and Alzheimer’s disease, but the pain mechanisms associated with severe degenerative or severe neurological impairment and associated conditions remain to be fully explained [24.25]. Even with a determined search for an underlying cause, one is frequently faced with the likelihood that the final diagnosis becomes a “medically unexplainable pain” [26], leading to a therapeutic dead‐end whereby without a diagnosis, treatment is often delayed or may not begin at all. In such cases, even with a potentially identified source, limited and effective communication only compounds the complexity of effective pain treatment.

Pain Assessment Tools

While individuals with ID are at increased risk for experiencing pain, often compounded by co‐occurring conditions, specific assessment tools designed for individuals with ID remain limited and have only emerged within the last two decades. In this section, we briefly outline a number of pain assessment scales (see Table 42.1) designed to evaluate pain specifically among children and adults with ID (for more detailed reviews specific to scale development, see Belew et al. [27]; Breau, McGrath, & Zabalia [3]). The scales reviewed in Table 42.1 were designed and developed specifically for individuals with ID, however scales from other vulnerable populations (neonates, elderly) have been adapted for use with children with ID (e.g. the revised FLACC) [28].

Table 42.1 Pain assessment tools for children and adults with intellectual disabilities (ID)

Pain Scale	Brief Description	Items	Psychometric Properties	Recommendations
Child Pain Scales
Pain Indicator for Communicatively Impaired Children (PICIC) Stallard et al.¹²	‐200 pain cues derived from caregiver interview narrowed to 6 main cues	6	‐Showed accuracy ‐Not retested for validity or reliability	‐Short and simple ‐Possible preliminary measure of pain
Pediatric Pain Profile (PPP) Hunt et al.³¹	‐Semi‐individualized measure providing predetermined categories of behaviors which can be added to by the parent/caregiver	20	‐Valid, reliable and sensitive measure for each individual child ‐When specific behaviors are added, the measure does not generalize across children	‐May distinguish individual child’s good days from bad days ‐May be well suited for monitoring pain for an individual over time
Non‐Communicative Children’s Pain Checklist‐Revised (NCCPC‐R) Breau et al.²⁹	‐Observational assessment tool quantifies pain responses observed by parents and caregivers ‐Post‐operative version available	30	‐Reliable and valid in detecting pain	‐Useful across populations and settings ‐Consistently accurate with short observation times and by those unfamiliar with the child
The Chronic Pain Assessment Toolbox for Children with Disabilities	‐Culmination of pediatric assessment tools created to implement standardized pain assessment practices in clinical settings	15	‐All assessment tools selected for use in the Toolbox are reliable and valid in screening and detecting pain	‐Useful when making real time clinical decisions for patients
Kingsnorths et al.³⁶
Adult Pain Scales
The Pain and Discomfort Scale (PADS) Bodfish et al.⁴² Phan et al.⁵³	‐Measures pain and discomfort during a standardized physical examination (PEP: pain examination procedure)	18	‐High inter‐rater reliability ‐Sensitivity to pain	‐Useful in isolating the location/source of pain
Non‐Communicating Adult Pain Checklist (NCAPC) Lotan et al.³⁵	‐Adapted the NCCPC‐R to assess acute pain in adults with ID	21	‐High internal consistency ‐Sensitive to pain	‐The NCAPC is recommended currently for assessing acute or procedural pain in adults with ID.

The scales developed for individuals with ID to date focus on identifying a variety of possible pain signs in children and adults [29–31]. These include vocalizations (e.g. cry, scream, moan), facial expressions, movement (both increased and decreased), change in muscle tone (increased and decreased), guarding/protection and changes in everyday activity (social interaction, eating and sleeping) [29, 32]. It is important to consider that children with more significant ID may show different behavioral signs than those with mild ID. For example, scores of adaptive function domains (social and communication) were significantly related to the types of pain behaviors observed in children with ID post‐operatively using the Non‐Communicating Child’s Pain Checklist‐ Postoperative Version (NCCPC‐PV) [33].

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