Multidisciplinary Assessment of Patients with Chronic Pain

Dennis C. Turk

James P. Robinson

This chapter deals with the multidisciplinary assessment of patients with chronic noncancer pain. In order to be specific, especially with regard to the medical evaluation of chronic pain patients, we organize the discussion around a typical and common chronic pain problem (e.g., persistent cervical spine pain). We note, though, that many of the concepts in the chapter are relevant to the assessment of virtually any chronic pain patient. In particular, concepts related to the assessment of psychological factors, social factors, and functional limitations have wide applicability.

A key premise in this chapter is that multiple factors influence the symptoms and functional limitations of patients with chronic pain. As a consequence, we believe that evaluation along multiple dimensions, performed by professionals with a variety of skills, provides important insights into the factors governing the reports of these patients and assists in treatment planning.

Conceptual Issues

CONUNDRUMS IN THE ASSESSMENT OF PAIN

How we think about symptoms such as pain influences the way in which we go about evaluating patients. Physicians and the lay public alike tend to assume that some underlying pathology is both a necessary and a sufficient cause of the symptoms reported and experienced by patients. Consequently, medical assessment usually begins with taking a thorough history and performing a physical examination, followed by, when deemed appropriate, laboratory tests and diagnostic imaging procedures in an attempt to identify or confirm the presence of an underlying pathology that causes the symptom (see later). However, over the years, research has revealed puzzling observations that challenge the presumed isomorphism between pain and organic pathology. For example, the exact pathophysiology underlying some of the most common and recurring acute (e.g., primary headache) and chronic (e.g., back pain, fibromyalgia [FM]) pain problems is largely unknown. Thus, it is common for patients to have pain that cannot be attributed unambiguously to an organic pathologic process. Conversely, many people have abnormalities on diagnostic tests but no pain. For example, studies using plain radiography, computed tomography (CT), and magnetic resonance imaging (MRI) reveal that more than 30% of asymptomatic individuals have structural abnormalities such as herniated disks, spinal stenosis, joint space narrow in degenerative knees, and torn rotator cuffs that would be accepted as valid explanations of pain if the individuals had been symptomatic.¹^,²^,³ Thus, we are confronted with a rather strange set of circumstances: people with no identified organic pathology who report severe pain and, conversely, others with significant pathology who are apparently pain-free.

When health care providers are unable to identify organic pathology that reasonably accounts for a patient’s reports of pain, they may assume that the reports reflect psychological factors such as personality characteristics, psychopathology, and malingering. A psychological evaluation may be requested to detect the psychological factors that underlie the patient’s reports. Thus, there is a duality where the report of symptoms is attributed to either somatic or psychogenic mechanisms. This dualistic perspective dates back at least to the 17th century and the philosopher René Descartes. The assumption that symptoms that cannot be explained by medical findings must originate from psychological distress is, albeit unfortunately common, overly simplistic and inconsistent with current scientific understanding. The dichotomous view is incomplete and, as described throughout this chapter, is not compatible with available research evidence or the current understanding of chronic pain.⁴

A CONCEPTUAL MODEL FOR ASSESSING PAIN

The conundrums described suggest that multiple factors likely contribute to persistent pain and related disability. There is a growing consensus that these consist of (1) genetic composition⁵; (2) physical pathology associated with trauma or disease; (3) alterations in the peripheral and central nervous system (CNS) attributable to the initial insult (peripheral and central sensitization); (4) psychological contributors including various types of psychopathology, prior learning history, and available coping resources (e.g., emotional support, financial resources, acquired coping skills); and (5) environmental influences (e.g., response by significant others, disability compensation, features inherent in the workplace) that all likely interact. A comprehensive evaluation should provide information about each of these factors. Examination of unique genetic contributions is in its infancy at this time and is generally not performed in clinical settings, although it will likely be gaining attention in the coming years. Thus, in this chapter, we describe a general strategy for assessing factors 2 to 5.

Pain Behavior

It is useful to begin a discussion of assessment of patients with chronic pain with the concept of pain behaviors. Pain is a subjective perception, and there is currently no objective way to know about the experience of pain other than by patients’ behavior. Pain behaviors include verbal behaviors (i.e., statements about pain). They also include nonverbal behaviors such as limping or wincing.⁶ These pain behaviors are sources of communication; they convey to others the presence and severity of pain.

The challenge for an examiner is how to interpret patients’ pain behaviors. Although these behaviors are sometimes determined entirely by an abnormal biologic process in the area of injury, they are typically also influenced by changes in nervous system encoding and processing of nociceptive signals; by a patient’s beliefs and appraisals, emotional status, and coping strategies; and by the social environment.

Classes of Variables Underlying Pain Behavior

We will return to more formal assessment of pain behaviors later in this chapter. For now, a useful way to conceptualize this challenge is to think of a prediction equation with multiple unknowns: PB = f(Xa₁, Xa₂ … Xa_an; Xb₁, Xb₂ … Xb_bn; Xc₁, Xc₂ … Xc_cn; Xd₁, Xd₂ … Xd_dn).

Where PB = the pain behavior that a patient demonstrates, and predictor variables are organized into four categories, such
that Xa₁, Xa₂ … Xa_an refer to biomedical factors at the end organ where the patient reports pain; Xb₁, Xb₂ … Xb_bn refer to alterations in nervous system function (especially CNS sensitization [CNSS]) that perpetuate pain after nociceptive impulses from the end organ have diminished or ceased; Xc₁, Xc₂ … Xc_cn refer to psychological variables; and Xd₁, Xd₂ … Xd_dn refer to social or contextual variables that influence pain behavior.⁷

The prediction equation emphasizes the multiplicity of factors that influence patients’ expressions of pain and highlights the dilemma facing an evaluating clinician. The dilemma is that it is extremely difficult to determine the weights that should be assigned to various factors for an individual patient. To make matters even worse, there is no consensus about what the possible variables within various categories are (e.g., to specify the types of psychological factors that may affect a patient’s pain behavior).

In accordance with the model, the discussion is organized around the assessment of medical factors, CNSS, psychological factors, and social factors in chronic pain patients. We also consider the assessment of the severity of functional incapacitation in these patients.

Assessment of Medical Factors

A careful medical evaluation is a basic element in a multidisciplinary evaluation of a patient with chronic pain. The general goals of such an evaluation are to (1) make a medical diagnosis, (2) determine whether additional diagnostic testing is needed, (3) make a judgment about the extent to which medical data regarding a patient adequately explain his or her symptoms and the severity of his or her apparent incapacitation, (4) determine whether there is any medical or surgical treatment that has a reasonable chance of reversing the pathophysiologic processes underlying the patient’s pain, (5) determine whether there are any symptomatic treatments that should be prescribed if a reversal of pathophysiology is not possible, and (6) establish the objectives of treatment.

FIGURE 23.1 Key issues to address in the medical evaluation of chronic pain patients.

The specific procedures that physicians perform and the differential diagnostic possibilities they entertain vary enormously with patients’ symptoms and presumed medical disorders. For example, the medical evaluation of a patient with pelvic pain is entirely different from the evaluation of a patient with neck pain. Also, the medical evaluation of a pain patient depends on the chronicity of the patient’s symptoms and the physical evaluations and diagnostic testing that the patient has already undergone.

In order to be reasonably specific, the discussion here focuses on the medical evaluation of patients with persistent neck pain, especially in the aftermath of a “whiplash” injury.

There is no uniformly accepted algorithm for evaluating neck pain patients. In fact, as will be discussed, clinicians differ sharply about some aspects of such evaluations. The approach discussed in the following section is summarized in Figure 23.1, which identifies key questions that should be asked in the evaluation of a patient with persistent neck pain.

ARE THERE RED FLAGS?

Although the assumption in this section is that the patient is undergoing evaluation for residuals of a neck injury, occasionally, the physician will find that the patient has misattributed his or her symptoms and is actually symptomatic because of a disease rather than because of any injury.

A general medical history that addresses issues such as weight loss or fevers should alert the physician to the possibility that a patient is symptomatic because of a disease such as an neoplasm or infection.⁸^,⁹

If symptoms appear to be the result of injury, what is the nature of the injury?

Neurologic injuries. The physician needs to be alert to clinical evidence of a cervical radiculopathy or a myelopathy. Evidence for these possibilities is obtained from the patient’s history (e.g., pain and paresthesias into an extremity in a segmental distribution) and a careful neurologic examination. Electrodiagnostic studies can provide additional evidence regarding the presence of a cervical radiculopathy¹⁰; MRI scans can provide evidence of anatomic compromise of nerve roots or the cervical spinal cord.¹¹^,¹²^,¹³^,¹⁴
Major skeletal injuries. When a history of significant trauma is elicited, radiologic studies are needed to rule out the possibility that a patient has a spinal fracture or a ligamentous injury severe enough to yield instability.¹⁴^,¹⁵^,¹⁶ Although these major skeletal injuries are often accompanied by spinal cord injury or radiculopathy,¹⁷ they may occur among individuals who are neurologically intact.¹⁸
Other musculoskeletal injuries (axial spinal pain). The overwhelming majority of patients with chronic neck pain do not have evidence of a neurologic injury or a major skeletal injury but present with localized axial cervical spine pain that suggests a musculoskeletal injury or with pain in a pattern suggesting referral from a joint in the cervical spine.¹⁹^,²⁰ These patients are often very difficult to evaluate medically because there are no physical examination findings or diagnostic tests that unequivocally identify the structural basis of axial cervical spine pain. In this ambiguous situation, it is important for the examining physician to be aware of the structures that might underlie a patient’s symptoms.
- Ligamentous injuries. Ligaments abound in the cervical spine, so pain felt to be ligamentous in origin could stem from various structures. The ligaments most often proposed as causes of axial cervical spine pain are the alar ligament, the posterior longitudinal ligament, and the facet joint capsular ligaments.¹⁵^,²¹^,²² Because ligaments are critical to the stability of the cervical spine, severe damage to them is often assessed by looking for instability. Most commonly, this gross instability is associated with major skeletal injuries and is diagnosed in emergency room settings. A more subtle type of ligamentous abnormality has been postulated to be identifiable based on an abnormal MRI signal from ligaments, such as high signal intensity on proton attenuation-weighted high-resolution MRI. In principle, these signal abnormalities could reflect ligamentous injuries that cause pain but are not severe enough to cause instability. Some investigators have reported that ligamentous injuries identified by abnormal MRI signals play a significant role in whiplash injuries and that the severity of self-reported disability among people with these injuries correlates with the severity of the MRI signal abnormalities.²³^,²⁴^,²⁵ However, longitudinal studies on whiplash patients as well as research on asymptomatic people and ones with neck pain secondary to cervical degenerative conditions rather than injury suggest that the MRI signals that some investigators have interpreted as indicators of ligamentous injuries should actually be considered normal variants or indicators of cervical degenerative disk disease.²⁶^,²⁷^,²⁸
- Disk pathology. It is widely accepted that cervical disk herniations can cause radiculopathies. But a more controversial issue is whether pathology of cervical disks can cause axial cervical spine pain and, if so, how such discogenic pain can be diagnosed and treated. Some investigators have proposed that cervical discogenic pain does occur and that it can be diagnosed via discography—a procedure in which imaging is performed after injection of contrast dye into a cervical disk and the pain response of the patient is assessed during injection of the dye and just after follow-up injection of a local anesthetic. The presence of an abnormal discogram, defined on the basis of some combination of the morphology of a disk and the pain responses of a patient during the procedure, is viewed as an indication that the disk accounts for the patient’s pain and that a cervical spinal fusion is the appropriate definitive treatment.²⁹ The evidence supporting discography as a means of identifying cervical discogenic pain is weak, with some reviews concluding that there is no compelling evidence to support its use³⁰^,³¹ and others specifically recommending against its use.³² Skepticism regarding cervical spine discography is bolstered by research on lumbar spine discography. This research has demonstrated a high false-positive rate for discography, a tendency for psychosocially stressed people to have an especially high false-positive rate, and failure of spinal fusion based on discography results to produce satisfactory results.²⁹^,³³ Although dueling literature reviews make it somewhat difficult to reach any definite conclusions about cervical discogenic pain,³⁴ a reasonable conclusion is that although discogenic pain is biologically plausible,³¹ no technology currently exists to demonstrate its presence in an individual patient or to provide treatment based on its suspected presence.
- Facet joint injury. Bogduk and colleagues³⁵^,³⁶^,³⁷ have asserted that facet joint injuries often underlie persistent cervical pain and have pioneered techniques for identifying painful facet joints on the basis of patients’ reports of symptoms during injection procedures designed to provoke or palliate pain. Using these techniques, they have reported that approximately 70% of individuals with persistent neck pain following motor vehicle collisions have pain mediated by one or more of the cervical facet joints. Equally important, they have demonstrated that when patients diagnosed with facet joint-mediated pain receive injections (facet neurotomies) designed to denervate the affected facet joint, approximately 70% experience prolonged symptom relief.³⁷^,³⁸ More recent research has supported the importance of facet joint pathology in whiplash pain, although the frequency was reported as 29% rather than 70%.³⁹ As with discography, prominent teams of reviewers have reached opposite conclusions about the prevalence of facet joint-mediated pain, the validity of the diagnostic procedures used to diagnose this kind of pain, and the efficacy of invasive therapies to treat it.³⁰^,³² It is beyond the scope of this chapter to try to resolve the discrepant assessments of facet joint-mediated whiplash pain, although we believe the evidence supporting it is more impressive than the evidence supporting discogenic pain.
- Muscle pain. Opinions about the prevalence and significance of muscle pain in chronic axial neck pain are, if anything, more divided than opinions about discogenic pain or pain associated with facet joint or ligamentous injury. Most investigators of muscle pain use the language and concepts developed by Travell and Simons,⁴⁰ who popularized the term myofascial pain and emphasized its importance as a cause of persistent musculoskeletal pain. Proponents of myofascial pain
  have argued that this is extremely common in patients with persistent neck pain. For example, one recent study found evidence of myofascial pain in 100% of a cohort 224 patients treated for chronic neck pain by primary care providers.⁴¹ But the quality of the data supporting the importance of myofascial pain in spinal disorders is questionable,⁴² and the term myofascial pain is not even mentioned in comprehensive reviews of neck pain (e.g., Côté et al.,⁴³ Hogg-Johnson et al.,⁴⁴ Holm et al.⁴⁵). Again, it is beyond the scope of this chapter to resolve the conflicting views regarding the importance of myofascial problems among patients with chronic neck pain. But a few observations are worth making. First, there are no accepted diagnostic tests for myofascial pain. Clinicians rely on the history and physical examination to make the diagnosis. Second, clinicians should be aware that many neck pain patients will describe pain that suggests irritation of muscles and will report tenderness to palpation of neck and shoulder girdle muscles. Third, there is uncertainty about the appropriate interpretation of these symptoms and reports during physical exams. Because pain that seems to be muscular is typically widespread and because CNS hypersensitivity is now recognized as at least one contributor to the pathophysiology of myofascial pain,⁴⁶ symptoms that some physicians construe as indicators of myofascial pain could instead be construed as widespread “nonanatomic” pain, or as pain secondary to CNSS rather than peripheral nociception.
FIGURE 23.2 Patient indication of pain location.
Widespread “nonanatomic” pain. As described earlier, physicians who practice musculoskeletal medicine try to explain symptoms following a musculoskeletal injury in terms of some structural lesion in joints, periarticular tissues, muscles, and nerves in the body region where the patient is symptomatic.⁴⁷ The first step in this approach is to elicit a patient’s symptoms and consider pathophysiologic processes that might reasonably account for them. But this approach founders when the symptoms of patients do not fit a pattern that suggests some discrete injury to a musculoskeletal structure. For example, Figure 23.2 is a pain drawing provided by a chronic pain patient who reported that she initially hurt her lower back pain when she lifted a heavy box on her job. Although the patient denied injuries other than her low back injury, the figure indicates that she was now experiencing widespread pain. In interpreting such figures, it is important to note that research has demonstrated that irritation of intervertebral disks and facet joints produces
characteristic patterns of referred pain⁴⁸^,⁴⁹ and that experts in myofascial pain have proposed characteristic patterns of referred pain from affected muscles. Thus, it is sometimes possible to explain widespread symptoms as indications of referred pain. However, the drawing shown in Figure 23.2 does not lend itself to such an interpretation because it does not conform to any known pattern of referred pain from an intervertebral disk, a facet joint, a ligament, or a muscle in the cervical region. The most plausible interpretation of such widespread pain is that it is a manifestation of altered perception based on CNSS (described later) or psychological factors.

ARE THERE RISK FACTORS FOR DELAYED RECOVERY?

It is important to evaluate risk factors for delayed recovery in a patient with chronic neck pain. Unfortunately, research on the validity of many potential indicators is lacking. Thus, the following list of indicators should be viewed as plausible candidates for consideration during the medical evaluation of a chronic pain patient rather than as proven predictors. Another caveat is that although some of the potential indicators refer to medical variables, others refer to psychosocial variables that might be evaluated better by a psychologist than by a physician.

Presence of a systemic disorder of the musculoskeletal system, such as rheumatoid arthritis or one of the muscular dystrophies
- Presence of general medical conditions that influence prognosis. For example, if a patient has severe cardiovascular disease, this may have implications for his or her ability to function in a physical therapy program. A patient who has had a stroke may have difficulty following medical directions.
- History of prior spinal injuries or of significant prior symptoms in the absence of injury
- Evidence of severe spondylosis
- High pain intensity
- Severe functional limitations on examination
Chemical dependency. The patient’s history in this domain is important because it may bear on the appropriateness of prescribing opioids or sedatives.
Sleep disturbance. Disturbed sleep is a common symptom reported by chronic pain patients, and most clinicians who treat these patients accept the premise that disordered sleep plays a role in perpetuating symptoms and disability.⁵⁰ Thus, if a patient reports significantly disturbed sleep, a treatment plan for him or her should include interventions to promote normalization of sleep.
Evidence of severe emotional distress
Disability and litigation issues

SPECIFIC EVALUATION PROCEDURES

The physician should gather at least some information on most or all of the issues outlined earlier. For factors that are not biomedical, it is important for the physician to at least identify areas of concern, so that follow-up evaluations can be provided by the appropriate specialists. Broadly speaking, the information will come from three sources: the patient’s history, the physical examination, and ancillary studies.

History

It is beyond the scope of this chapter to discuss the elements of a thorough history. It is worth noting, though, that in evaluating a chronic pain patient, the physician should pay careful attention to certain historical items that are considered only cursorily in other clinical settings. In particular, the physician should be careful to assess the patient’s history with respect to chemical dependency, sleep disturbance, apparent severity of incapacitation, and his or her status with respect to litigation and compensation.

Physical Examination

A neurologic and musculoskeletal examination should be performed on all patients with chronic cervical spine pain. In a patient with a normal neurologic examination, a musculoskeletal evaluation of the neck (including assessment of soft tissue hypersensitivity and range of motion) is often not especially revealing.¹⁹ In particular, it is virtually impossible to identify a distinct pain generator on the basis of a physical examination of such patients. But some useful information can be gleaned from a musculoskeletal examination. First, the physician can determine the severity of the patient’s functional limitations, especially restricted motion of the spine and pain-inhibited weakness of neck and extremity muscles. Second, the physician can check for hyperalgesia over muscles of the neck and shoulder girdle as well as more widespread hyperalgesia involving remote sites. Third, the physician can determine whether the patient demonstrates significant apprehension and “nonorganic signs.”⁵¹^,⁵² Research indicates that patients with nonorganic signs usually have significant somatic anxiety. This emotional distress may impair their recoveries and may be a focus of treatment.

One caution about physical examination concerns the reliability of the assessment of factors such as range of motion. Evidence suggests that the interrater reliability of commonly performed physical examination tests is limited,⁵³^,⁵⁴ and thus, it is important to determine whether findings on a single examination are consistent with a patient’s history, previous examination findings, and diagnostic tests.

Ancillary Studies

Although laboratory studies and electrodiagnostic evaluations are occasionally helpful in the assessment of patients with chronic neck pain, imaging studies are the procedures that are done the most frequently. There is significant controversy about how and when imaging should be done on chronic pain patients. When judged against guidelines, one-third to twothirds of spinal CT and MRI imaging may be inappropriate.⁵⁵^,⁵⁶ High imaging rates can be problematic because irrelevant but alarming findings, including herniated disks, are common in asymptomatic people.²^,⁵⁷ Without attempting to resolve these controversies in any systematic way, we suggest the following: (1) for pain involving a trauma, it is reasonable to check for the possibility of a fracture or significant spinal instability using plain x-rays of the spine; (2) additional imaging is generally not needed for such a patient, unless there is clinical evidence of a neurologic injury. In that case, an MRI scan is generally indicated; and (3) CT scans and bone scans usually have a limited role—they can be obtained to identify an occult fracture or an inflamed facet joint.

Another type of diagnostic test for patients with chronic neck pain is one that uses local anesthetic blocks of structures thought to be the pain generators. The logic underlying this approach is that if a patient reports dramatic relief following a local anesthetic injection of a structure in his or her neck, it is reasonable to assume that the structure is functioning as a pain generator for the patient. The most widely used procedures of this kind are nerve root blocks, medial branch blocks, and discography. As discussed earlier, there is controversy about how valuable local anesthetic blocks are in the diagnosis of patients with chronic neck pain. We believe that nerve root blocks can play an important role in identifying the structural basis of radicular symptoms and are often used to guide surgical decision making. We believe that medial branch blocks should be used selectively but can be helpful in the management of patients
who do not have evidence of nervous system sensitization or psychological or social processes that might interfere with their recovery. We are skeptical of the value of discography in neck pain patients.

CONCLUSION

The previous discussion addresses the medical evaluation of chronic pain within the context of patients with cervical spinal pain. We have gone into some detail in order to make the point that medical decision making in relation to cervical spine pain is far from simple. It is our opinion that in order for pain patients to participate fully in evaluations of nonmedical factors contributing to their pain, they need to be confident that their problem has been evaluated thoroughly from a medical perspective. Thus, it is important for physicians participating in a multidisciplinary team either to have a lot of expertise in medical aspects of the problems that afflict their patients or to consult with colleagues who have this expertise.

Assessment of Central Nervous System Sensitization

During the past 35 years, CNSS has emerged as an important phenomenon in chronic pain.⁵⁸^,⁵⁹ Early research on nonhumans demonstrated that they predictably developed CNSS in response to tissue injury and that the CNSS was manifested by characteristic changes in the behavior of dorsal horn neurons in the spinal cord, including a lowered response threshold and an expansion of receptive fields.⁵⁹ Expansion of receptive fields was postulated to correlate with referral of pain and lowered response threshold with hyperalgesia.⁶⁰^,⁶¹

Several methods have been developed to assess CNSS in humans. Among them is quantitative sensory testing, which has shown that people with chronic pain demonstrate reduced thresholds to multiple modalities of sensory stimulation, including pressure, thermal, and electrical stimuli.⁶²^,⁶³ These abnormalities occur when stimuli are applied to the specific location of the reported pain and even to body regions where patients do not experience clinical pain.

Another approach has been to study withdrawal reflexes in response to potentially noxious stimuli. Relevant studies have shown that these reflexes can be elicited among chronic pain patients at lower stimulus intensities than the ones required to elicit the reflexes in healthy people.⁶⁴^,⁶⁵

Still another promising method for assessing CNSS is functional MRI (fMRI). Several investigators have used fMRI methodology to identify brain areas associated with processing of noxious stimuli and have found that patients with chronic pain (e.g., FM, chronic low back pain, and chronic pelvic pain) demonstrate more dramatic activation of these areas than healthy controls.⁶⁶^,⁶⁷

Findings from the aforementioned lines of inquiry have been interpreted by several researchers as evidence of CNSS among people with persistent pain⁶⁰ and as a central feature in the development of neuropathic pain.⁶⁸ Although these proposals have not been conclusively proven, the widespread belief among many neuroscientists and pain specialists that CNSS is a major factor in chronic pain has implications for the evaluation of the condition. At a conceptual level, CNSS challenges the simple dichotomy between organic pain and psychogenic pain that held sway in the orthopedic literature of a generation ago.⁴⁷ At the level of clinical evaluation of an individual patient, the absence of definitive tests to determine the presence of CNSS makes it difficult for a clinician to rule in or out the hypothesis that it is affecting symptoms. The ambiguity introduced by CNSS is increased by the fact that although it is usually identified during an examination by a physician, it is not a medical diagnosis in the usual sense. For example, the International Classification of Disease, 10th edition, does not include any codes that can be used to designate that a patient’s pain is a reflection of CNSS. Also, no clear delineation has been drawn between CNSS versus psychological factors as a cause of persistent symptoms. The evaluation of CNSS is given a separate section in this chapter because of its ambiguous middle ground status between traditional medical processes and psychological processes.

At a practical level, clinicians who treat chronic pain patients need to be aware that CNSS may be playing a role in the reports of their patients. One reason for this is that in the presence of CNSS, many of the inferential rules followed by clinicians when they interpret reports of pain are invalid because the rules are based on a simple model of an isomorphic correspondence between symptoms and dysfunction of tissues (nerves, joints, periarticular tissues, muscles) in the region where the patient indicates pain. The inferential rules are simply not valid when CNSS has occurred. For example, stocking glove numbness has long been considered a nonphysiologic complaint, but it can logically be interpreted as a result of CNSS.⁶⁹ Another practical issue is that clinicians should not expect to find a one-to-one relation between symptoms and a definable structural lesion in a patient whose pain is mediated by CNSS rather than by ongoing nociceptive input from specific body locations. Finally, clinicians need to be cautious about invasive therapies for patients whose pain is mediated by CNSS. The problem is that the pain of such patients may be generated primarily by spontaneous activity within the nervous system rather than by ongoing nociception from peripheral tissues, so that surgical alterations of tissues have little impact on it.

Given the potential importance of CNSS in the symptoms and functional limitations of pain patients, it would be highly desirable to have sensitive and specific tests to determine whether it is occurring in individual patients. Unfortunately, although the methods described earlier and several others have been examined in research on CNSS,⁶³^,⁶⁷ no definitive test for its presence is available for clinical use. In clinical settings, practitioners usually rely on various indirect indices to decide whether CNSS is playing a major role in their patients’ symptoms.⁷⁰

Assessment of Psychosocial Factors

A comprehensive psychological evaluation of a pain patient is a fundamental component of a multidisciplinary evaluation. It addresses the specific psychosocial, behavioral, cognitive, and contextual factors such as current mood (anxiety, depression, anger), interpretation of the symptoms, expectations about the meaning of symptoms, and the responses to the patient’s symptoms by significant others (e.g., family members, coworkers), each of which contributes to the subjective experience of pain. This type of information should be included in the development of a comprehensive treatment plan.

PSYCHOLOGICAL FACTORS AS CAUSES VERSUS CONSEQUENCES OF CHRONIC PAIN

Psychological Factors as Causal Agents in Development of Chronic Pain

Patients often resist psychological evaluations because they intuitively sense that the outcome of such evaluations might be the conclusion that their pain is a result of psychological dysfunction rather than the injury to which they attribute their symptoms. Indeed, early reports suggested that preexisting psychopathology or neurotic traits might be the underlying mechanisms for unremitting chronic pain.⁷¹^,⁷² As early as 1953, Gay and Abbot⁷¹ mentioned “neurotic reactions,” noting that particular psychological factors predisposed an individual to chronic problems after an injury. In 1982, Blumer and Heilbronn⁷² postulated that
patients with chronic symptoms had a distinct personality type that predisposed them to developing chronic pain—“pain-prone personality.” They specifically suggested that persistent symptoms offered a solution for their preexisting neurosis. There has been little empirical support indicating that the majority of chronic pain patients manifest character traits comprising a common and unique disposition.⁷³ However, some studies have noted the high lifetime prevalence of psychiatric diagnoses observed in chronic pain patients,⁷⁴ and prospective studies that followed healthy individuals who subsequently develop back pain² and from acute injuries to the presence of disabling pain⁷⁵ have observed that premorbid psychological factors were the best predictor of persistent pain chronicity.

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