Chapter 6. Evaluating the Patient with Chronic Pain

Pain is a complex multidimensional symptom. It is determined not only by actual or potential tissue injury and normal and abnormal activity of the nervous system, but also by the patient’s personal beliefs, mood, previous painful experiences, psychosocial stressors, coping mechanisms, and motivational factors. Evaluation of a patient with chronic pain should take into consideration all of these factors. Unfortunately, there is no single test or scale that can measure pain comprehensively, reliably, or objectively. Thus, assessment of pain requires a thorough history and physical examination in combination with other diagnostic tools. Several visits may be required to elucidate relevant medical and pyschosocial factors. The patient’s motivation for the evaluation must be clarified early (i.e., whether there are issues of litigation or disability affecting the patient’s pain, and whether he or she perceives the potential to control pain as coming from without or within). To do this, it is important to listen well and not overly structure the interview. Chronic pain patients need validation. Without it, they cannot offer their trust, and trust is vital for treatment compliance and a successful outcome.

Pain assessment is a dynamic process that evolves with the pain management plan. The pain evaluation should be used to localize the source of pain; to determine its quality, pattern, and intensity; to define exacerbating and attenuating factors; and to assess how environmental and behavioral influences affect the pain. Clinicians should always try to make a diagnosis before implementing a treatment plan, recognizing that jumping to a premature conclusion might result in inappropriate treatment or harm to the patient. It is also necessary, at times, to rethink the diagnosis, despite previous and thorough workups.

Pain should be broadly defined as nociceptive (somatic or visceral), neuropathic, or idiopathic. Toward this end, pain location is of utmost importance to accurate diagnosis. It may be well localized, as in entrapment neuropathy (e.g., carpal tunnel syndrome), widespread and diffuse (e.g., fibromyalgia), or regional (e.g., musculoskeletal pain). Patterns of radiation may help determine the site of pathology, such as in cervical or lumbar radiculopathy. Radicular pain (along a dermatome) implies involvement of a nerve root. Pain may also be referred, as in visceral pain, when it is felt over a particular area of skin that is embryologically associated with but anatomically distant from the source of irritation. Accurate characterization of the pain’s location and pathophysiology provides the rationale for treatment. Tables 6-1, 6-2, and 6-3 provide examples of referred pain contrasted with clinical findings associated with nerve root versus peripheral nerve pathology.

Detailed history taking at the first visit and a focused history (with emphasis on response to recent intervention) on subsequent visits is extremely beneficial. In many pain centers, the physician obtains a history after reviewing forms (see Appendix B) completed by the patient before the first interview. Some of the important points to be covered in this part of the evaluation are:

• 1. Location of pain
• 2. Character of pain
• 3. How and when the pain started
• 4. Is it continuous or intermittent?
• 5. Exacerbating and relieving factors
• 6. Effect of certain positions and activities on pain
• 7. Effect of stress on the pain
• 8. Effect of alcohol and other substances on pain
• 9. Is there an associated sleep disturbance?
• 10. Is there an associated mood disturbance?
• 11. Effect of pain on functioning at work or school
• 12. Effect of pain on quality of life, including social, sexual, and family interactions
• 13. Effect of pain treatment on cognitive, social, and sexual function
• 14. Motivation: issues of secondary gain (i.e., disability or psychological attention from partner, parents, or spouse)
• 15. Is a lawsuit involved?
• 16. Who, if anyone, does the patient blame for the pain?

Beware of attributing new pain to an already defined process. For example, someone with ankylosing spondylitis can still develop a herniated disk, and cancer pain may change or worsen because of disease spread, tolerance to medications, side effect of treatment, or a new psychosocial stressor.

The physical examination starts with the first clinical interaction between the patient and clinician. It begins with how the patient responds to the initial greeting: getting up, walking, sitting down, and posture during these activities. Appearance (general health, weight, muscle bulk, and grooming), attitude and behavior (degree of distress and reactions to specific examination maneuvers), and gait (ataxia, walking with a limp, or requiring a cane or walker) can provide important information. The presence or absence of masses or lesions, signs of injury or trauma, and limb asymmetry regarding skin, hair, nails, or temperature changes should be noted. Alignment of the spine (scoliosis, kyphosis, loss of curvature) and range of motion (ROM) should be noted. Pain-exacerbating maneuvers, such as the straight-leg raising test, Spurling’s maneuver of the neck, Patrick’s test of the hip, and spinal ROM tests, may yield important diagnostic information. Joint shape, swelling, redness, and tenderness should be noted. Measurement of vital signs may prove useful in evaluating stress, pain (which alters vital signs in young children), and side effects of medication.

Focused neurologic and psychiatric examinations also start with the first clinic visit. If the patient is able to give a clear and adequate history, a formal mental status examination is usually unnecessary, but range of affect (facial expression) and its congruency with language content and mood can provide important clues to the presence or absence of depression or anxiety. The effect of analgesics on higher intellectual function should be documented to help with future medication trials and to interpret problems of mental status. And unless the patient suffers from a headache or cranial nerve pain or dysfunction (i.e., trigeminal neuralgia or trigeminal neuropathy), the cranial nerve examination can generally be simplified by checking facial symmetry and eye movements (for a detailed outline, see Table 6-4). Experience best guides the clinician in the directed examination; however, subtle and sometimes significant findings may be missed by using a screening technique.

Results of the motor, sensory, and deep tendon reflex examination should be viewed together. Patients with lumbar or cervical radiculopathy may have more than one measurable objective sign or abnormality, although pain in a nerve root distribution may be the only symptom. If a single nerve or nerve root is involved, motor, sensory, and reflex abnormalities should coincide with and not contradict one another (see Tables 6-2, 6-3, 6-5, and 6-6). If a nerve plexus is involved, the situation is more complex and may require more extensive neurologic or electrodiagnostic evaluation. It is helpful to know that the boundaries of sensory-motor deficits are less clear in plexopathies than they are in peripheral nerve injury and that pain can occur without such deficits. Progression of sensory dysfunction, even outside of the originally involved area (i.e., allodynia), may indicate centralization of pain or disordered sensory processing in the spinal cord and not necessarily psychiatric overlay, as is often supposed.

We recommend functional motor assessment as an initial evaluative tool for the motor system, followed by a more focused examination of any abnormal findings (Tables 6-2, 6-3, 6-4, 6-5, 6-6, and 6-7). For example, if patients with back pain can rise from a chair without using their arms and can easily walk on tip-toes and heels, they are unlikely to have lower extremity weakness on manual-motor testing.

Some tests are more nerve root–specific than others. Great toe extension is mostly controlled by the L5 nerve root, whereas dorsiflexion of the foot involves nerve roots L4 through S1. It is vital to distinguish true muscle weakness from pain-limited strength and lack of effort. “Giveway” weakness may be indicative of either. Feigned unilateral weakness, an uncommon problem, is harder to maintain when both limbs are assessed at the same time. Table 6-7 summarizes some likely “nonorganic” signs and symptoms that are referred to as “illness or pain behavior.”

The sensory examination should include response to light touch, light pressure, pinprick or cold (i.e., metal object or alcohol swab because pain and temperature are carried in the same pathway), and vibration and assessment of proprioception or joint position sense. If the patient’s Romberg stance is stable, significant loss of vibratory and position sense is unlikely, but still possible. The affected skin area, which almost always manifests hyperesthesia, should be tested at the end of the examination. Allodynia should be sought in terms of light touch, light tapping, mechanical movement, and cold stimuli. Hyperpathia is elicited by fairly rapidly applying pinpricks to the focal area. What at first appears to be a diminution in pain sensation suddenly becomes an abnormally intense and prolonged discomfort lasting beyond the time of stimulation. When pain has become chronic and local tissue injury has healed, the persistence of allodynia, with or without hyperpathia, points to a neuropathic rather than nociceptive pain process. This may have important implications for further workup and treatment. Nociceptive pain, on the other hand, is generally associated with hyperesthesia that resolves with healing.

Examination of gait is not only helpful in screening for motor, sensory, or balance dysfunction, but it can also help evaluate the toxicity of some analgesic medications (high levels of some antiseizure medications used for pain may cause a broad-based gait and loss of balance, otherwise known as truncal ataxia). Conversely, the absence of a widely based gait in a patient complaining of difficulty balancing raises the question of astasia-abasia or functional sway. If present, the latter does not negate a physical basis for pain, but raises the question as to whether psychologic factors influence the degree of patient suffering.

Methods of evaluation may not be as equivalent as they first appear. Electromyography and neural blockade is a case in point. Electromyography, including the electromylogram (EMG) and nerve conduction tests (NCT), can help rule in or out a myopathy, neuropathy, radiculopathy, or plexopathy accompanying a painful condition. It can also help determine chronicity. Several spinal and nerve root levels may be tested in a single session. Reflex arcs of the spinal cord can be evaluated and peripheral neurologic findings on the physical examination confirmed, but EMG cannot measure pain. EMG cannot measure small-fiber dysfunction (i.e., as caused by diabetes) and should not be attempted until 2 to 3 weeks after the onset of symptoms. This minimizes the chance of false-negative results. EMG and NCT are extremely operator dependent, in terms of both technique and interpretation.

Selective nerve root blockade and spinal injection into vertebral disks (diskograms) and zygahypophyseal (facet) joints or the epidural space may prove diagnostic or therapeutic but offer no clues to chronicity. Except for diskography, multiple levels of testing are not easily or wisely done during a single visit, because specificity is lost. Although the usefulness of EMG, NCT, and selective nerve root blockade may overlap, information obtained through one does not necessarily negate the need for the other. If in doubt about which diagnostic test is most appropriate, ask a colleague with advanced understanding of that particular field.

Choosing the appropriate mode of imaging can be difficult, the consequence of which may hasten or slow the time to accurate diagnosis. A general guide to the commonly used techniques is presented in Table 6-8. Advice should be sought from knowledgeable colleagues for specific case applications.

No single tool or instrument can measure pain fully and objectively in a clinical setting. But several measurement instruments have been developed to assess the most clinically relevant aspects of pain and ways in which it affects the patient’s life. These tools are either easily used but limited in what they measure (unidimensional scales) or require time to apply and psychological expertise to interpret (multidimensional scales).

Unidimensional Instruments, Scales, and Indices

In clinical practice, unidimensional and self-report scales offer a simple, useful, and valid method for assessment and monitoring of a patient’s pain. Unidimensional scales measure only the intensity of pain.

Numeric Rating Scale (NRS) or Verbal Rating Scale (VRS)

This is the simplest and most commonly used scale to evaluate pain. On a scale of 0 to 10, where 0 represents “no pain” and 10 the “worst imaginable pain,” the patient chooses a number to describe the pain intensity. Advantages of this scale are that it is simple and reproducible, it is easily understood by most patients, and small changes in pain can be measured. Its major disadvantage is its inability to reflect anything more than the intensity of pain. Ramifications of pain on mood (or vice versa) are not so easily measured.

Visual Analog Scale (VAS)

The VAS is very similar to the NRS or VRS except that the patient puts a mark on a nongradated 10-cm line, with one end labeled as “no pain” and the other as “worst pain imaginable.” Using the VAS, pain can be evaluated on a 0 to 10 scale and can be described as such. The advantages and disadvantages are very similar to the NRS, but the VAS is used more commonly in clinical pain research. VAS results do not always match, but the discrepancy itself can prove useful, since it stimulates a more in-depth evaluation.

Verbal Descriptor Scales

With verbal descriptor scales, patients are asked to describe their pain by choosing descriptors from a list of adjectives reflecting pain intensity. One example is a five-word scale denoting pain as mild, uncomfortable, distressing, horrible, or excruciating. A major limitation of this scale is that patients often select moderate descriptors rather than extremes to appear more “reasonable” or may select extremes rather than more moderate descriptors when their level of distress is very high. This should prompt a search for confounding factors, such as anxiety or fear, which can greatly affect the level of pain or suffering.

Faces Pain Rating Scale

Evaluating pain in children younger than 8 years old is extremely challenging because of their inability to fully describe pain or understand pain assessment forms. The Faces Pain Rating Scale depicts sketches of facial expression, ranging from a happy, smiley face to a very distressed and teary face. Several versions are in common use. In evaluating children in pain, their cognitive-developmental level, pain self-support, pain behavior, and physiologic parameters, such as variation in blood pressure and heart rate, must also be taken into account. The Faces Pain Rating Scale may also be useful in developmentally disabled patients, cognitively impaired geriatric patients, and sometimes in patients who do not speak English (when no interpreter is available).

Multidimensional Instruments, Scales, or Indices

These instruments provide more detailed information about the patient’s pain than do unidimensional scales. They are especially useful in the evaluation of complex pain in patients whose suffering is likely multifactoral in origin. However, these tools are relatively cumbersome and time-consuming, requiring expert interpretation. They are usually reserved for use in clinical research or in-depth multidisciplinary evaluations at comprehensive pain management centers. Pain psychologists often employ a battery of such tests in conjunction with the psychiatric interview. Only a few are mentioned here for the purpose of illustration.

It is important to reemphasize that no single assessment tool can fully evaluate a person’s pain. Just as magnetic resonance imaging cannot replace the acumen of the clinician, so these measurement tools are limited to an adjunctive role in evaluation of the neuropsychologic pain. The value of these tests lies in their appropriate use by trained individuals.

Minnesota Multiphasic Personality Inventory (MMPI)

This instrument is a long and complex questionnaire that requires caution in interpretation (its scales are based on the general population, not a chronic pain patient population). A number of scales are generated, which may lead to a false sense of confidence in the ability of the test to assess pain. The ability to predict outcome of treatment is variable. The test is better at predicting who is not likely to return to work than who is. Thus, the degree to which this tool is helpful depends greatly on the application, knowledge, and skill of the clinician using it. Many pain centers use an abbreviated and modified version called the MMPI-2.

Mcgill Pain Questionnaire (MPQ)

Historically, this is one of the most commonly used multidimensional instruments. Patients select descriptive terms from groups of words ranked in order of severity. Pain location is also sketched on a human figure drawing. Present and previous pain experiences are noted, and all of this is integrated into a general analysis of the patient’s pain experience. The MPQ requires some patient sophistication in the use of language, reducing the value of the test considerably if applied indiscriminately.

Brief Pain Inventory (BPI)

The BPI asks patients to rate the pain at its worst, least, and average intensity, as experienced at the time of evaluation. It also asks patients to present the location of their pain on a schematic diagram of the body. The BPI is a cross-cultural instrument and is particularly useful in clinical pain research.

As we have discussed, no single scale or test is able to fully evaluate a patient with chronic pain, but a combination of the patient’s history and physical examination, diagnostic tests, and some of the assessment tools can be very helpful. Each pain center or clinician can develop a pain assessment form dictated by the type of pain problems most often encountered in their referral group. Appendix A is the pain assessment form used by the pain management center at the Beth Israel-Deaconess Medical Center (BIDMC) in Boston. Patients complete the center’s assessment form before their first appointment. This approach is a classic consultative model. Referral is made by primary care or treating clinician, via a referral letter or form provided by the BIDMC pain center. Once the referral is received, a pain management specialist reviews the information and decides on the best line of action, based on the nature of the pain and urgency of the situation. Urgent appointments are scheduled with patients for whom immediate interventions may prevent chronic pain and disability, such as patients in the early stages of reflex sympathetic dystrophy (recently renamed complex regional pain syndrome, type 1) or postherpetic neuralgia.

All patients are required to complete the assessment form before their first visit. Some patients are selected for a “comprehensive pain evaluation” based on the chronicity and complexity of their pain, response to previous interventions, and complicating factors, such as substance abuse, psychiatric illness, or factors associated with possible secondary gain. The comprehensive pain evaluation requires completion of modified versions of the Beck Depression Inventory (BDI), the MMPI, and other behavior assessment tools before the first visit. These patients are then scheduled to see a team composed of one or two physicians, a nurse, a psychologist, and a physical or occupational therapist, all on the same day. Then, the full multidisciplinary team (i.e., clinicians who have personally seen the patient plus those who have not) discusses the evaluation team’s findings and impressions and arrives at a realistic, practical, and long-term plan.

The cornerstone of this model is that pain specialists act as consultants in coordinating short-term and long-term care of a variety of patients with chronic pain. Once the patient is stabilized on a certain regimen or has reached a medical end point, patient management is taken over by the referring clinician. The patient must have a primary care clinician to be seen. The pain specialist does not “take over” responsibility of the patient’s care but may be heavily involved in it, at least initially. Where possible, the primary care clinician should prescribe the pain medications, once the dose has been stabilized. This allows closer monitoring of a patient’s health over time and minimizes the chance of accidental drug-drug interactions. The fewer people prescribing for a patient, the better.

A modification of this approach (used where state health plans or insurance coverage is more restrictive) begins with the pain physician’s initial evaluation on referral by another clinician. The pain physician then refers to other clinicians (not necessarily in his or her clinic) as necessary and as authorized by the third-party payer. As the third-party payer milieu continues to evolve, more pain centers may have to adopt this potentially less expensive and slower approach. One of the authors (Goodwin) and Kim J. Burchiel, MD, Chairman of the Department of Neurological Surgery at the Oregon Health and Science University, believe that a potentially successful means of doing this is via a coordinated network of persons, clinicians, and services who are financially independent of each other yet complementary in terms of skills, philosophy, and training. Such interdisciplinary or interdepartmental cooperation could provide a depth and breadth of resources unlikely to be available in a smaller, single department–funded multidisciplinary pain center. If alternative medicine is specifically and openly included in interdisciplinary patient care and not just used as an adjunctive complementary or alternative approach, the care can then rightly be referred to as integrative pain medicine.

Finally, in some states, such as Oregon, patient evaluation by a pain specialist, or an expert on the physiologic or anatomic system that is painful (e.g., urologist, orthopedist, gastroenterologist), is required by law so that a primary care provider can prescribe long-term opioids for the management of nonmalignant pain without concern of criticism by the medical board of examiners. This particular type of evaluation may or may not require a team approach, depending on the complexity of the situation.

Evaluating a patient with chronic pain can be time-consuming and frustrating, because clinicians must rely greatly on the patient’s subjective report and the somewhat limited results of objective tests. An understanding of central and peripheral neuroanatomy and pathophysiology, visceral innervation, and musculoskeletal function is essential for interpretation of findings by review of the history, physical examination, and other diagnostic tools. If done correctly, the evaluation alone can prove therapeutic; just having a diagnosis can alleviate stress. It is the first step in building the physician-patient relationship and therapeutic alliance. It is important always to listen to and believe in your patients and involve them in the decision-making process. The clinician should be empathic, supportive, and honest, neither promising too much nor removing all hope. There is a big difference between stating, “There is nothing I can do,” and, “There is nothing more that can be done.” The suffering patient is a human being in distress, not a disease. Tests and measurement tools aid in diagnosis and treatment but cannot replace a thorough history and physical examination. Several visits may be necessary before the picture becomes clear. If the preceding approach is followed, especially within a multidisciplinary or interdisciplinary setting, then there is a reasonable chance that a correct diagnosis will be followed by appropriate management.