INTRODUCTION — Chronic pain is one of the most common reasons that patients seek medical attention, and affects more than 20 percent of children and adults in the United States alone [1]. Chronic pain is defined as that which lasts longer than three to six months, or beyond the duration required for normal tissue healing after an acutely painful event. Chronic pain results from combined biologic, psychologic, and social factors, and most often requires a multifactorial approach to evaluation and management.
This topic will discuss the evaluation of chronic non-cancer pain in adults. Management of chronic non-cancer pain, assessment and management of cancer pain, and the use of opioids for chronic non-cancer pain, are discussed separately.
●(See "Approach to the management of chronic non-cancer pain in adults".)
●(See "Pharmacologic management of chronic non-cancer pain in adults".)
●(See "Use of opioids in the management of chronic non-cancer pain".)
●(See "Assessment of cancer pain".)
Evaluation and management of specific chronic pain conditions are discussed in multiple separate topics.
EPIDEMIOLOGY AND ECONOMIC IMPACT — Approximately 30 percent of patients in developed countries report moderately severe or severe pain that persists longer than six months [2].
●Incidence – A 2020 Centers for Disease Control and Prevention (CDC) analysis of data from the National Health Interview Survey estimated that 20.5 percent (50.2 million) of adults in the United States had chronic pain and 10 percent of adults (24.4 million) had high-impact chronic pain with work limitations [1,3]. The highest incidence of chronic pain and high impact chronic pain was among women. Chronic pain in the past three months was more common in patients who lived in more rural areas. High impact chronic pain was more common in non-Hispanic white compared with Hispanic and non-Hispanic Asian adults (8.4, 5.3, and 2.2 percent respectively), with no significant differences between non-Hispanic white and non-Hispanic black adults. A 2011 review has found a higher prevalence among American Indians and Native Alaskans than in the United States general population [1,4].
The prevalence of chronic pain may be more than 40 percent in older adults, with osteoarthritis and low back pain the most common etiologies [5]. The 2016 National Survey of Children's Health reported a 6 percent prevalence of chronic pain among United States children [6].
●Type of pain – In a study of results from the National Health Interview Survey for 2019, of those reporting chronic pain the most common locations of were lower extremity pain (hip, knee, and foot, 44.1 percent), and back pain (40.9 percent), followed by upper extremity (31.7 percent, headache [13.6 percent], abdomino-pelvic pain [8.2 percent] and tooth or jaw pain [6.5 percent]) [3]. Neuropathic pain may occur in as many as 10 percent of the general population [7,8]. Common conditions associated with chronic pain are shown in a table (table 1).
●Impact – The costs of chronic pain in the United States alone are difficult to determine, but in 2010 was estimated at over $560 billion due to direct medical costs, lost productivity, and disability programs (excluding cost of care for children, military personnel, institutionalized adults, and personal caregivers) [2]. In the international Global Burden of Disease Study for 2010, the conditions that caused the largest number of years lost to disability in the United States included low back pain, musculoskeletal disorders, and neck pain [9].
Chronic pain has a range of psychosocial impacts, and often can lead to discord in the patient's living situation, underemployment, and disability. In addition, if opioids are prescribed for chronic pain, there is a high incidence of misuse, dependence, and opioid use disorder. (See "Prescription drug misuse: Epidemiology, prevention, identification, and management", section on 'Epidemiology'.)
DEFINITION OF PAIN — Pain is an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage. Pain is a complex biopsychosocial phenomenon, as reflected in the 2020 revised definition of pain from the International Association of Pain (IASP) [10] (see 'Chronic pain in context' below). The IASP definition of pain and associated notes that inform evaluation and management are shown in a table (table 2).
When an acutely painful condition persists beyond the usually expected 6 to 12 week time course for most healing from disease or injury, it has transitioned from acute to chronic pain. Pathophysiological processes may or may not include active biomedical causes, psychological factors from incident disease and/or from pre-existing disorders of mood and cognition, or social factors [11,12]. Personal or family social issues and economic disruptions, preceding physical or social neglect, sexual or substance abuse, and other adverse or traumatic life events may all affect pain perception [13].
Pain can be classified as nociceptive, neuropathic, and/or nociplastic , and the distinction between these types of pain influences the plan for treatment (see "Approach to the management of chronic non-cancer pain in adults", section on 'General approach' and 'Pathophysiology of pain' below). Definitions of the types of pain and related terms are shown in a table (table 3).
The United Kingdom 2021 National Institute for Health and Care Excellence (NICE) Guidelines for assessment and management of chronic pain propose differentiating primary from secondary chronic pain conditions [14]. This classification was in response to new International Classification of Diseases (ICD)-11 coding that allowed for fibromyalgia, complex regional pain syndrome, and non-specific low back pain to be specified as diseases in their own right [15,16]. Such classification relies upon accurate diagnosis of an underlying condition, versus finding that the impact of pain is disproportional to an observed injury or disease, though the guideline notes that primary and secondary pain can coexist. We do not use this classification, which risks a false dichotomy between pain that is real versus unreal as a result of a psychosocial disorder. We view chronic pain as a disease unto itself, regardless of how it starts.
PATHOPHYSIOLOGY OF PAIN — The physiology of pain is complex, and an in-depth discussion is beyond the scope of this topic. Briefly, painful stimuli arising in the periphery are received by specialized nociceptors that selectively respond to a range of aversive stimuli (eg, temperature, pressure, pH). Peripheral nociceptive input is transmitted through the dorsal horn of the spinal column where interneurons modulate and project signals to a distributed range of central nervous system (CNS) structures, including brainstem, limbic, subcortical, associative, and somatosensory brain regions. Pain is a dynamically linked spatiotemporal event, experienced through multi-segmental [17] descending inhibitory and facilitatory signals arising from both the periphery and from the brain (figure 1).
Transmission of pain and modulatory signaling involves multiple dynamic and widely distributed bidirectional pathways of excitatory and inhibitory receptors and neurotransmitters, which are targets for the treatment of pain. Drug treatment for chronic pain can target several sites, including neuroreceptors (eg, opioid receptors), ion channels (eg, calcium and sodium channels), and neurotransmitters (eg, norepinephrine and serotonin). The major analgesic targets and related drugs are shown in a table (table 4). Non-drug treatments targeting mostly peripherally-acting mechanisms include acupuncture, dry needling, manipulation, and transcutaneous and peripheral nerve stimulation, among others. Non-drug treatments that are mostly centrally-acting include cognitive-behavioral therapies, sleep hygiene, and spinal neurostimulation devices, among others. Non-pharmacologic treatments that target both peripheral and central pain processes include exercise, guided motor imagery, and yoga, among others.
Nociceptive pain — Nociceptive pain is caused by stimuli that threaten or result from bodily tissue damage. Nociceptive pain is expected after surgical and other acute traumatic injury, and is associated with a range of musculoskeletal and visceral conditions that involve inflammatory, ischemic, infectious, or mechanical/compressive injury. Chronic pain may occur with persisting nociceptive signaling from medical disorders that persist despite aggressive treatment for underlying cause, such as with degenerative, inflammatory, and neoplastic diseases.
Neuropathic pain — Neuropathic pain results from a maladaptive response to damage or disease of the somatosensory nervous system, and consists of a central and/or peripheral disorder of pain modulation [7]. Often, damage to the nervous system results in only a loss of function (eg, numbness, weakness), but with neuropathic pain there is a gain of function (pain). Neuropathic pain can occur in the absence of active noxious stimulus, or as an exaggerated response to minor or moderate nociceptive stimulus [18,19].
Causes of neuropathic pain are multiple and varied, and include peripheral (eg, painful diabetic neuropathy, postherpetic neuralgia, nerve trauma, autoimmune disorders) and CNS sites of initial injury or disease (eg, stroke or spinal cord injury, multiple sclerosis, trigeminal neuralgia); but the sustaining physiology may very much involve both the peripheral nervous system and the CNS, as described for both painful diabetic neuropathy and phantom limb pain [2,20-22]. Often, the etiology is unknown. The pathophysiology and manifestations of neuropathic pain are highly variable among individual patients and etiologies.
Neuropathic pain has traditionally been subdivided by the disease or anatomic location of the inciting injury. However, emerging evidence suggests that combining the pain description (burning, intermittent, constant) and physical examination (abnormal pain due to a stimulus that does not normally provoke pain [allodynia], increased pain from a stimulus that normally provokes pain [hyperalgesia], or loss of sensation) may better help categorize patients (known as "phenotyping") so that more specific therapies can be offered [23,24].
Nociplastic pain — The term "nociplastic," pain was coined to recognize that many patients have pain that is not fully described by tissue injury (nociceptive pain) or nerve injury or disease (neuropathic pain) [25]. Nociplastic pain is defined by the IASP as pain that results from altered nociception, without evidence of actual or threatened tissue damage that causes activation of peripheral nociceptors, and without evidence for disease or a lesion causing the pain [25]. This change was made in response to advances in many fields of pain research and efforts in ICD-11 to qualify a number of better understood chronic pain conditions as diseases in their own right [15]. The term "nociplastic," pain may not yet be commonly used clinically; it conveys similar concepts to terms such as "central sensitization," and "centralization," when characterizing pain. Nociplastic pain can accompany both nociceptive pain and neuropathic pain and may be accompanied by more broad sensitivity to stimuli (sound, light, odors).
Altered pain sensory processing and impaired central pain modulation appear to play a prominent role in many chronic pain conditions such as fibromyalgia [26], a number of rheumatic and musculoskeletal disorders (eg, osteoarthritis [27,28]), common chronic visceral pain conditions (eg, irritable bowel syndrome [29], chronic pancreatitis [30], chronic pelvic pain [31], interstitial cystitis [32], and sickle cell disease [33]). These conditions are characterized by the neurophysiologic phenomenon of "central sensitization," or "nociplasticity," which may also play a role in the transformation of acute pain into chronic pain. They often present clinically with findings of wide-spread pain, hyperalgesia and allodynia (table 5) [34]. Even if nociplastic pain is present, somatic or bodily processes often still play an important role in ongoing pain (eg, in osteoarthritis), but they may not be the primary explanation for the level, extent, or impact of the pain.
Pathophysiologic changes in brain function have been demonstrated with functional magnetic resonance imaging (fMRI) and other imaging techniques [35,36]. Mechanisms of dysfunctional neuroplastic transformation are incompletely understood and are areas of active research [37-39]. Mechanisms, diagnosis, and the approach to treatment of centralized pain are discussed separately. (See "Overview of chronic widespread (centralized) pain in the rheumatic diseases", section on 'Definitions and pain mechanisms'.)
RISK FACTORS FOR DEVELOPING CHRONIC PAIN — A number of patient factors increase the risk of developing chronic pain, including genetics, patient fears and expectations, prior poor pain-related treatment outcomes, psychiatric and behavioral co-occurring conditions, adverse social issues, older age, and long-term opioid use. Acute pain may transition to chronic pain for a variety of reasons, including the nature of disease or injury, and if important psychosocial factors are left unaddressed in the months following onset of painful injuries and diseases. Identification and treatment of risk factors that contribute to pain chronification may reduce the likelihood of patients transitioning from acute pain to chronic pain (table 6). (See 'Patient evaluation' below.)
Some injuries and surgical procedures are associated with a high risk of persistent pain (eg, hernia repair, breast surgery), and poorly treated postoperative pain may increase the risk of chronic pain. As an example, properly managed acute pain may prevent persistent pain after total knee arthroplasty (TKA) [40], and may reduce the long-term use of opioids after TKA [41].
Family history of chronic pain may increase the risks of some medical conditions associated with chronic pain (eg, headaches, fibromyalgia, inflammatory diseases) and/or behavioral health conditions (eg, depression, anxiety, posttraumatic stress disorder [PTSD] [42,43], substance abuse disorders [44]).
A 2020 review raised the possibility of an increase in chronic pain following the COVID-19 pandemic [45], since acute infections can trigger chronic pain syndromes and patients may report pain as part of post-COVID-19 syndrome [46].
CHRONIC PAIN IN CONTEXT — Pain is experienced in developmental, social, and emotional contexts [47]. Whether pain is acute or chronic, it is a biopsychosocial phenomenon [48], and when pain has become chronic its management typically requires multidimensional structured assessment and treatment (table 2). Negative emotions and expectations, such as fear and catastrophizing about impact of pain on the patient's job, parenting, and other life roles, can amplify the perception of pain. Fears of relapse when pain occurs in cancer survivors may heighten pain severity [49].
Socioeconomic status, geography, access to health care, availability of exercise, and culture all impact the pain experience and treatment options. Chronic pain should be evaluated understanding these issues, as well as the patient's age and developmental stage of life, ranging from childhood through adulthood and into older age. Evaluation and management of pain must consider the sensory, cognitive, and emotional factors that change over the lifespan, the roles of caregivers, and should use developmentally appropriate assessment measures [50-52]. (See "Pain in children: Approach to pain assessment and overview of management principles" and "Treatment of chronic non-cancer pain in older adults".)
Other aspects of the patient's life may also affect treatment decisions. For instance, pregnancy is often associated with low back pain, and pregnancy can complicate the choice of medication treatment options for chronic pain, particularly the use of opioids [53,54]. (See "Overview of management of opioid use disorder during pregnancy" and "Methadone and buprenorphine pharmacotherapy of opioid use disorder during pregnancy".)
A patient-clinician interaction that creates a positive and healing therapeutic relationship can be expected to improve treatment compliance, engagement, and outcome response [55]. The psychophysiologic placebo response [56] can be effective therapy for patients with chronic pain, as it is for much of medicine, particularly if the patient and clinician develop a long-term relationship in an outpatient setting (eg, a primary care clinical setting) as opposed to an urgent care facility or emergency department.
PATIENT EVALUATION — Evaluation of the patient with chronic pain requires a systematic search for biomedical causes and contributing factors, psychologic evaluation, assessment of physical capability (including job and/or life role) and sleep function, and determination of social factors that may increase pain severity and worsen clinical outcomes. Assessment should include comprehensive medical assessment, and pain-focused history and physical examination (table 7).
Past medical and surgical history — The medical history and review of systems can help determine the etiology of chronic pain (eg, diabetes, history of cancer, rheumatic diseases) (table 1) and may reveal conditions that affect the choice of therapy, eg, avoidance of sedatives and opioids in the setting of sleep disordered breathing [57] or chronic pulmonary disease [58], considerations of drug clearance and metabolism in the setting of renal or liver dysfunction, or potential risk of antidepressants in patients with cardiovascular disease [59]).
Review of systems — A "pan-positive," review of systems may suggest conditions associated with nociplastic sensory hypersensitivity [60] (ie, central sensitization, discussed above) and may support a syndromic pain diagnosis, such as chronic fatigue, headache, visceral pain, or widespread conditions such as fibromyalgia. (See "Clinical features and diagnosis of myalgic encephalomyelitis/chronic fatigue syndrome" and "Clinical manifestations and diagnosis of fibromyalgia in adults".)
Social and family history — The patient's social history may reveal issues that affect the development and treatment of chronic pain, including early childhood exposures to traumatic events and/or threatening community environments (and so risk for posttraumatic stress disorder [PTSD]) [61]; marital/partner stability; educational attainment and employment history; past and current family construct; and the use of tobacco, alcohol and other at-risk drugs for poor pain treatment outcomes, including long-term opioid use [62]. (See 'Risk screening' below.)
Social issues may increase the risk of chronic pain and the risk of long-term opioid use [62], and affect the response to therapy. Stability of the patient's living situation, employment history or disability, level of education, and use of tobacco or alcohol should all be assessed during evaluation for chronic pain. Child care or other caregiver requirements, transportation barriers, or concerns about missed time at work may reduce access to care options.
Where services are available, patients with social challenges may be referred to case workers or social services for assistance. Collaborative care models that include a wide range of health professionals and care coordinators can also increase treatment engagement, align expectations, and so improve outcomes [63].
Family history of chronic pain may also identify predisposition to pain-associated medical conditions (eg, headaches, fibromyalgia, inflammatory diseases) and/or behavioral health conditions (eg, depression, substance abuse disorders).
Psychiatric comorbidity — We routinely screen patients with chronic pain for psychiatric and behavioral problems (see 'Pain severity and impact' below) since many patients presenting with high impact chronic pain also have histories of primary psychiatric comorbidity [64]. Depression, anxiety, PTSD [61], substance abuse, and other psychiatric disorders can present obstacles to diagnosing and treating many pain syndromes [65]. Patients with longstanding or complex pain problems should be treated with a multidisciplinary approach that includes an evaluation by and close collaboration with a behavioral and/or medical health professional (based on indications for pharmacologic support) who can diagnose and treat the psychologic/psychiatric aspects of the condition (table 8). (See 'Pain severity and impact' below.)
Symptoms of concurrent psychiatric problems can worsen chronic pain. Sleep disturbance, loss of appetite, lack of energy, and diminished physical activity contribute to an increasingly debilitated state and amplify the patient's pain and hopelessness. Chronic pain can worsen depression and anxiety, and interfere with successful antidepressant treatment [66]. Patients with chronic pain commonly describe a lack of pleasure, catastrophic thinking, reduced motivation, hopelessness, social isolation, fatigue, and an absence of control in their lives. Chronic pain is associated with a higher risk of suicide, suicidal ideation, and suicide attempts [67,68]. (See "Suicidal ideation and behavior in adults", section on 'Chronic pain'.)
While appropriate treatment of depression may improve pain, especially in somatically expressive instances of depression, we do not conflate treating depression with treating pain. Managing mood is an essential aspect of care for many patients with chronic pain but rarely represents the only treatment. In patients for whom the symptoms of depression are a complicating feature and sometimes natural sequel to life with chronic pain, antidepressant treatment can relieve the distress and emotional intensity with which physical pain is experienced [69]. (See "Pharmacologic management of chronic non-cancer pain in adults", section on 'Antidepressants'.)
Chronic pain disorders with identifiable pathophysiologic causes overlap with many common conditions that are attributed to "functional" causes, such as irritable bowel syndrome, and so can be mistakenly treated as simply psychiatric or behavioral disorders (table 5).
Pain assessment — Pain assessment informs the choice of therapy and should be used to monitor the effect of therapy. Every effort should be made to make a specific pain diagnosis or, when several different pain conditions are present, several diagnoses, to avoid the imprecise and non-specific "chronic pain" label. Pain assessment can be confounded by beliefs, attitudes, and implicit biases of evaluating clinicians, especially when clear evidence of tissue injury may no longer be present [70]. For patients with a pre-existing diagnosis of chronic pain, a thoughtful effort should be made to consider whether a new condition may be the cause for a new pain complaint, especially when a significant change in the characteristics or pattern of pain are present.
Pain history — We initiate assessment of the history of the patient's pain with the questions represented by the acronym "OLDCARTS," which are used to broadly characterize the pain and are shown in a table (table 9). Since patients often present with more than one pain complaint, each pain problem that is medically and potentially diagnostically distinct (eg, neck pain and right knee pain) should be characterized as thoroughly as the clinical situation warrants. Rather than focusing on the currently predominant pain issue, looking at all the areas of pain often results in a clearer understanding of the patient and appropriate treatment options.
Importantly, treatment notes and records should be reviewed, including previous beneficial and failed therapies (ie, drug doses and duration, behavioral health treatments, physical therapy, interventional procedures, prior surgeries). The authors have often found that many prior treatments are called "ineffective" due to inadequate dose, duration, or timing; or "failed" due to poor communication of rationale and value (eg, a referral for psychologist or physical therapist) or side effects that could have been potentially been avoided (eg, slower titration or alternative same category drug). (See "Cancer pain management with opioids: Optimizing analgesia" and "Use of opioids in the management of chronic non-cancer pain".)
Location of pain — We ask patients to complete a body diagram map as a key initial step of pain assessment and continue its regular use during routine follow-up (figure 2). The body pain diagram delineates the location and extent of pain, and distinguishes between focal or radiating pain and widespread or total body pain. Patient descriptions of pain location may not fit with clinicians' use of medical terms (eg, hip pain, sciatica) and the pain diagram can help clarify. We ask patients to indicate all of their painful areas on the body diagram, which may reveal a less localized process. Widespread pain may result from a systemic inflammatory disorder, such polymyalgia rheumatica, or suggests a hypersensitivity disorder, such as fibromyalgia. New areas of pain on the body diagram can be compared easily with previously described symptomatic sites. We find that the body diagram can facilitate treatment planning and subsequent assessment. Body diagrams are available as an interactive computerized format, or can be completed on paper. When chronic pain is "widespread," and especially with combined musculoskeletal and visceral locations, and when symptoms include fatigue, poor sleep, headache, and cognitive complaints, we recommend concurrent use of the Assessment of Fibromyalgia Survey, a patient self-report survey for the assessment of fibromyalgia based on criteria in the 2011 modification of the ACR preliminary diagnostic criteria for fibromyalgia (form 1). Diagnosis of fibromyalgia is discussed in detail separately. (See "Clinical manifestations and diagnosis of fibromyalgia in adults".)
Pain characteristics — The choice of an appropriate initial therapeutic strategy is dependent upon an accurate evaluation of the cause of the pain and the type of chronic pain syndrome. In particular, neuropathic pain should be distinguished from nociceptive pain. Patient reported pain descriptors most characteristic of neuropathic pain include tingling or pins and needles, burning, and shooting or electric shock. While these characteristics are included in most of the published screening tools for neuropathic pain [71-74], an accurate history and physical examination remains the clinical standard for identifying the presence of neuropathic pain. (See 'Physical examination' below.)
Pain severity and impact — Chronic pain and the efficacy of therapy should be assessed in terms of function and quality of life, in addition to pain intensity. Numeric pain rating scales are not adequate sole metrics for the severity of pain [75]. We agree with practice guidelines for the treatment of chronic pain, including the 2016 Centers for Disease Control and Prevention (CDC) guideline for prescribing opioids for chronic pain, which recommend that pain and pain therapy should be assessed with a multidimensional set of measures, including patient reported outcomes. This approach is consistent with the multidimensional experience of chronic pain [54,76].
For multidimensional assessment of pain severity and impact in the primary care setting, we ask patients to complete the following questionnaires for initial evaluation and at each follow-up visit. This assessment consists of the body diagram and approximately 10 questions that can be completed quickly on paper or using a computerized record (table 7).
●The validated Pain intensity, pain interference with Enjoyment of life and General activity (PEG) score includes three questions that are scored on a scale from 0 to 10 [77]. The PEG tool allows for more than a single item pain intensity score, since improvement in baseline of enjoyment and quality of life and general function are key goals of chronic pain treatment. Each is scored on a 0 to 10 out of 10 numeric rating, and either cumulatively added or individually scored, and subsequently tracked for improvement at each pain-related visit. Extremely elevated individual or total PEG scores suggests poor pain care status. Use of the PEG tool allows the clinician to follow specific treatments directed toward improving enjoyment of life and general function (eg, identifying what defines enjoyment of life for that individual, identifying how specific performance goals can be achieved). These domains are assessed and reassessed longitudinally over time relative to baseline; this report is reformatted to be shared with the patient at each visit to support engagement (form 2).
●The validated Four-item Patient Health Questionnaire (PHQ-4) (table 10) for anxiety and depression includes two items from the General Anxiety Disorder (GAD-7) score and two items from the Personal Health Questionnaire (PHQ-9) depression measure [78]. When PHQ-4 score is greater than 5, more detailed screeners are recommended, and we recommend the full PHQ-9 (table 11), the full GAD-7 (calculator 1), and the Primary Care 5-question PTSD screener (table 12) [79,80]. This allows for more precise targeting of mental health conditions and type of behavioral health specialty provider to refer to when necessary.
The Defense and Veterans Pain Rating Scale (DVRPS) is a visually appealing and easy to administer five-item chronic pain assessment tool, with 0 to 10 out of 10 ratings for pain intensity and pain interference with activity, sleep, mood, and stress (form 3). DVRPS has been validated in United States military medicine primary care health setting [81], but it is not yet generalizable for other primary care settings.
●We evaluate all chronic pain patients for problems with sleep. At each visit, the authors ask patients to rate 0 to 10 out of 10 how much pain interferes with falling sleep, and whether pain interferes with staying asleep.
Management of pain is the primary method for improving sleep in patients with chronic pain, while sleeplessness increases pain intensity and frequency [82]. In our experience, treatment of insomnia often improves patient reported function, quality of life, and satisfaction with treatment. Thus, improving sleep quality and duration is an important goal for optimal pain relief. Difficulty with initiating sleep often responds well to sleep hygiene self-management techniques, and when necessary, to cognitive-behavioral therapy for insomnia [83]. Difficulties with sleep maintenance may be a symptom of depression anxiety, and/or PTSD, and specialty referral may be needed. Treatment of insomnia is discussed in detail separately. (See "Overview of the treatment of insomnia in adults".)
We screen patients for obstructive sleep apnea (OSA) with the STOP-Bang questionnaire (table 13). OSA is common and important to identify in patients with chronic pain, especially since patients commonly report fatigue during the review of systems, and many patients are taking sedatives and/or opioids. Patients who are deconditioned due to pain may be overweight or obese, and therefore at increased risk of OSA. (See "Clinical presentation and diagnosis of obstructive sleep apnea in adults".)
Physical examination — A comprehensive physical examination should be performed for all patients with chronic pain, including during pain specialist consultation, to identify areas for treatment and anatomic and physiologic abnormalities potentially relevant to the pain complaint. As examples:
●A skin rash or nail bed stippling may support a diagnosis of an inflammatory arthritis or myopathy.
●Widespread pain hypersensitivity to palpation may suggest a more complex centralized pain process.
●Hyperreflexia may indicate spinal cord myelopathy (eg compression, syrinx, or multiple sclerosis) in a patient reporting focal muscle tenderness in the neck or numbness in a distant site, or drug withdrawal, among other possible causes.
●A painful site focused examination may be appropriate to evaluate a well-localized pain in a patient without pre-existing chronic pain.
●Presence of numbness or reports of abnormal sensation, motor or reflex deficits, or pain in response to light touch (allodynia), or pinprick (hyperalgesia) likely supports a neuropathic pain diagnosis. A higher degree of pain reported to ordinarily a low-level applied pressure may support a diagnosis of fibromyalgia, central sensitization, or other widespread pain disorder (table 3).
●Altered gait or range of motion may point to functional limitations that can be addressed with physical rehabilitation.
Diagnostic studies for the evaluation of pain — Appropriate laboratory, imaging, and other testing can be helpful to evaluate or follow certain painful conditions.
Imaging studies — Imaging with a plain radiograph is useful if a specific site of bone or joint pain related to an injury or disease is not clearly diagnosed by history and physical exam, or if surgery or an interventional procedure such as a joint injection is contemplated. However, routine radiographs without a specific diagnostic or therapeutic target are frequently low yield. Radiograph findings may not correlate with pain severity due to mechanisms of sensitization, and treatment for a sensory hypersensitivity condition may be more effective than targeting peripheral causes [84,85].
It is well recognized that magnetic resonance imaging (MRI) of the spine [86] may identify pathology of uncertain significance, without clear correlation with clinical severity or outcomes. It is important to communicate to the patient that abnormal, "degenerative" MRI findings may be quite normal for the patient's age, in order to prevent worrisome notions and catastrophizing thoughts of danger and risk that worsen rather than improve pain management. Many radiology experts and imaging centers have added interpretative comments to normalize common degenerative findings as "to be expected" [87,88]. Indications for imaging for back pain and the limitations of imaging are discussed separately. (See "Evaluation of low back pain in adults", section on 'Indications for imaging' and "Evaluation of low back pain in adults", section on 'Limited utility of imaging'.)
Diagnostic nerve blocks — Diagnostic procedures, such as selective peripheral nerve anesthetic, can be used to localize a potential cause at a specific painful site, but a short-acting anesthetic block does not typically provide durable pain relief. A local anesthetic block may increase the patient's tolerated range of motion, and thereby facilitate physical therapy. Pain relief from spinal (axial) nerve blocks (eg, medial branch block for facet pain) may indicate a role for a more durable focally destructive sensory nerve radiofrequency ablation procedure. (See "Approach to the management of chronic non-cancer pain in adults", section on 'Interventional therapy for chronic pain' and "Cancer pain management: Interventional therapies", section on 'Neural blockade'.)
Selective nerve blocks should be avoided for patients with widespread pain and/or high psychosocial distress measures, as assessed by PEG or PHQ-4 scores (see 'Pain severity and impact' above). For these patients, a selective nerve block will be low yield and may result in clinical worsening because of unmet expectations, increased frustration with care, delay in effective therapies, and unnecessary cost.
Electrodiagnostic testing — Electrodiagnostic testing (eg, nerve conduction studies) may be useful to define a compressive focal neuropathy, such as one derived from a spinal root (ie, radiculopathy), a peripheral nerve (eg, carpal tunnel), or to determine if neuropathic pain is caused by a sensory mono- or polyneuropathy (eg, diabetic neuropathy). Before ordering such a study, which can be painful, consider whether the study will contribute meaningfully to the clinical diagnosis and treatment plan. Consultation with a neurologist or rehabilitation medicine specialist may help determine the need for electrodiagnostic testing or other evaluation. In our specialty clinic we often detect a peripheral neuropathy on examination and make the diagnosis of diabetes, pre-diabetes, or vitamin deficiencies with routine clinical laboratory testing while avoiding electrodiagnostic testing. (See "Overview of polyneuropathy", section on 'Diagnostic evaluation'.)
Risk screening — When prescribing opioids long-term, the 2017 United States CDC guideline for prescribing opioids for chronic pain recommends risk screening measures be used as a routine opioid prescribing practice. These include review of the applicable prescription drug monitoring program (PDMP) database [89], urine drug testing before and during opioid therapy [90], and patient assessment for risks of overdose and opioid use disorder (including abuse and dependence) [91,92]. For patients who use or may use opioids, we use one of several available questionnaires to assess substance use disorder, such as the brief 4-item TAPS-1, the Opioid Risk Tool (ORT) (form 4), or Current Opioid Misuse Screen (COMM) (table 14 and form 5), or Screener and Opioid Assessment for Patients with Pain (SOAPP) (table 15 and form 6), or CAGE-AID. TAPS-1 has been validated in primary care as a triage tool [93]. None of the other instruments are well validated, so choice among them will be based on clinical judgment and provider preference (table 8).
Risk assessment prior to opioid prescription and during opioid therapy, including medical issues (eg sleep apnea, chronic obstructive pulmonary disease [COPD]), misuse screening tools, prescription drug monitoring databases, and urine drug screening, are discussed in detail separately. (See "Use of opioids in the management of chronic non-cancer pain" and "Urine drug testing for patients with chronic pain".)
The CDC checklist, which includes risk prevention and assessment, is a useful tool when prescribing opioids for patients with chronic pain (table 16).
REFERRAL TO A PAIN SPECIALIST — Patients who may benefit from referral to an appropriate pain specialist fall into two broad overlapping groups.
●Patients for whom interventional pain treatment may be appropriate – These patients often have these characteristics:
•Localized pain with anatomic correlates (imaging, physical exam)
•Pain not responsive to initial conservative care (ie, treatment that is potentially of equal or more benefit and less risk)
•Distress and mood reasonably well controlled
•Desire to avoid surgery
•Appropriate expectations
●Patients with complex difficult to treat pain – Reasonable criteria for referral to a pain specialist or multidisciplinary pain center include the following:
•Persistent pain that significantly impacts function, quality of life, anxiety, and/or depression that has not responded to management by the treating primary or specialty care provider.
•Persistent pain that cannot be explained and requires treatment.
•Pain that may be appropriate for interventional treatment.
•High-risk or complex pain-related pharmacology or polypharmacy (high dose opioids, sedatives, multiple agents).
•Persistent neuropathic pain that has not responded to first-line treatments.
•Need for multidimensional care (medical management, rehabilitation, mental health treatment).
In our practice many patients referred for interventional treatments have the best outcomes when also engaged in multidisciplinary care. Similarly, patients initially treated with multidisciplinary care may ultimately benefit from interventional therapy.
COVID-19 IMPLICATIONS FOR CHRONIC PAIN — The implications of the COVID-19 pandemic on chronic pain in general and in patients who recover from the infection are not yet clear. This issue is discussed separately. (See "Approach to the management of chronic non-cancer pain in adults", section on 'COVID-19 implications for chronic pain' and "COVID-19: Evaluation and management of adults with persistent symptoms following acute illness ("Long COVID")", section on 'Persistent symptoms'.)
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Chronic pain management".)
SUMMARY AND RECOMMENDATIONS
●Types and cause of pain
•Chronic pain can be classified as nociceptive, neuropathic, and/or "centralized," and the distinction between these types of pain has implications for the plan for treatment (table 3). (See 'Definition of pain' above.)
-Nociceptive pain is caused by stimuli that threaten or result from bodily tissue damage. (See 'Nociceptive pain' above.)
-Neuropathic pain consists of a central or peripheral disorder of pain modulation, as a result of a maladaptive response to damage or pathology of the nervous system. (See 'Neuropathic pain' above.)
-Nociplastic pain (also called centralized pain) results from altered pain sensory processing and impaired central pain modulation. (See 'Nociplastic pain' above.)
•Pain is experienced in developmental, social, and emotional contexts (table 2). Thus, evaluation of the patient with chronic pain requires a search for a biomedical cause, psychologic and social evaluation, and assessment of physical function and sleep. (table 7) (See 'Chronic pain in context' above.)
●Pain assessment
•Pain assessment informs the choice of therapy and should be used to monitor the effect of therapy. Every effort should be made to determine the cause of the pain and whether the pain is neuropathic, nociceptive, or both. (See 'Pain characteristics' above.)
•The pain assessment should include the history of the pain, location and characteristics of the pain, evaluation of severity and impact, and a pain focused physical examination. At each visit, we assess patients with screening tools for pain characteristics, pain intensity and impact, and mood, and ask about initiation and maintenance of sleep (table 7). (See 'Pain assessment' above.)
•When diagnosis remains uncertain, we screen for central sensitization (using the widespread pain assessment tool) (form 1) and occasionally perform a more detailed evaluation for neuropathic pain. (See 'Pain characteristics' above.)
●Screening
•For patients who have evidence of distressed mood on initial screening, we screen further for anxiety, depression, and posttraumatic stress (table 7 and table 8). (See 'Pain severity and impact' above.)
•For patients who use opioids or for whom opioids are considered, we screen for risk of opioid misuse or opioid use disorder with a screening tool (table 8). Prior to prescribing opioids, we check the prescription drug monitoring program (PDMP) database and perform a urine drug test. (table 16) (See 'Risk screening' above.)
●Diagnostic studies – Imaging studies, diagnostic nerve blocks, and electrodiagnostic testing may be helpful for diagnosis of conditions that may cause chronic pain. (See 'Diagnostic studies for the evaluation of pain' above.)
●Referral – Patients with complex, difficult to treat pain should be referred to a pain specialist or multidisciplinary pain center for evaluation and treatment. (See 'Referral to a pain specialist' above.)
