Abstract
Chronic pain is defined as an unpleasant sensory and emotional experience arising from actual or potential damage to tissue, lasting longer than 3 months. An increasingly common clinical diagnosis, chronic pain is a major cause of disability, affects nearly 1 in 5 Americans, and costs $261 to $300 billion in health care expenditures annually. Significant increases in the prescription of opioids over the past three decades for the treatment of acute and chronic pain have contributed to the opioid abuse epidemic currently affecting the United States; misuse of opioids can be life threatening, as more than 20,000 died from prescription medication overdoses in 2015. Treatment of chronic pain can be very challenging at times and requires a multidisciplinary approach to care. This chapter provides a framework for the evaluation of chronic pain and addresses evidence-based management strategies.
Epidemiology
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Approximately 15-22% of Americans suffer from chronic pain.
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Chronic pain costs society approximately $600 billion annually: $261 to $300 billion in health care costs and $297 to $336 billion in related compensation costs, lost wages, and reduced productivity.
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More than 400 million workdays are lost each year secondary to chronic pain.
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Evaluations for spine and musculoskeletal disorders account for approximately 70 million physician office visits and 130 million outpatient, hospital, and emergency department (ED) visits annually.
Definitions
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Pain is an unpleasant sensory and emotional experience arising from actual or potential damage to tissue. It can be influenced by genetics, epigenetic biological processes, psychological responses, and societal and cultural norms.
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Chronic pain is ongoing or recurrent pain, lasting more than 3 months or beyond the usual course of acute injury, that adversely affects the individual’s well-being.
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In chronic pain, the structural and chemical function of the nervous system is altered through sensitization, which makes it physiologically distinct from acute pain (see Chapter 21 ), although acute pain can lead to chronic pain through a process termed chronification .
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Chronic pain may be nociceptive, neuropathic, or mixed. It serves no evolutionary function but contributes to the development and persistence of disability.
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Nociceptive pain: derived from detection of potentially damaging noxious stimuli by nociceptors
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Often described as Somatic, Referred, Radicular, or Postoperative
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Persistent pain of unclear etiology may be due to underlying malignancy
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Neuropathic pain: generated without adequate stimulation of sensory nerves
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Caused by nerve injury, and can affect both peripheral and central nervous systems
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Can occur in conjunction with nociceptive pain
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History
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It is important to establish good clinical rapport with the patient, first achieved during the initial encounter.
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Collect a comprehensive history. Special focus should be given to:
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Clinical course of pain (onset and inciting source of pain, how the pain has evolved since its onset, etc.)
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Pain functional and emotional impairment along with pain intensity should be assessed (see Defense and Veterans Pain Rating Scale [DVPRS], Chapter 21 ). Measuring only pain intensity to quantify pain and guide therapy is no longer acceptable.
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Pain character to help distinguish between types of pain (burning or electric shocks consistent with neuropathic pain versus cramping, classically describing nociceptive visceral pain)
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Aggravating and alleviating pain factors (e.g., associations of pain with activities, weather, stressors, or mood)
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Associated symptoms (such as weakness, numbness, loss of function, bladder, or bowel incontinence)
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Previous pain treatments and their effect on the patient’s function
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Assess for impact of pain on social, physical, occupational, and sexual function, and overall quality of life. Use of validated scores such as National Institutes of Health (NIH) Patient-Reported Outcomes Measurement Information System (PROMIS) self-report measures can help quantify this impact.
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Obtain past medical history:
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Psychiatric
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There is a bidirectional relationship between chronic pain and depression.
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Studies have shown individuals with chronic pain are at an increased risk of depression, and those with depression are at an increased risk for chronic pain.
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Many medications used for management of psychiatric conditions can affect chronic pain symptoms and treatment options.
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Substance Abuse
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Addiction in the setting of chronic pain can complicate the evaluation and treatment of the presenting complaint.
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The prevalence of substance abuse in those with chronic pain is 2-25%.
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It is important to screen for a personal or family history of substance abuse.
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The risk of drug use or abuse should be quantified using a validated screening tool (e.g., Opioid Risk Tool [ORT]).
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Medical Illness
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Medical comorbidities requiring use of certain chronic medications may limit treatment options (drug-drug interactions, medication side effects, etc.).
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Outside influences such as ongoing litigation and disability claims can complicate the clinical picture. It may be necessary to explore competing self-interest issues hindering therapeutic goals.
Physical Examination
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Physical examination will vary based on patient’s report of pain symptoms.
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Vital signs (typically not elevated with chronic pain as they are in acute pain)
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Evaluation of all chronic musculoskeletal pain should include a systematic assessment of:
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Gait, posture, muscular symmetry or atrophy, observed rashes
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Range of motion and strength testing
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Neurologic evaluation of light touch, pinprick, and deep-tendon reflexes
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Allodynia is the experience of pain from non-painful stimuli (e.g., light touch). Allodynia should raise suspicion for underlying neurologic cause of pain.
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Provocative maneuvers (e.g., Spurling test evaluating for nerve root disorder; straight-leg-raise evaluation for lumbosacral nerve root lesion; Patrick sign evaluating for sacroiliac joint pain or intra-articular hip pathology; Tinel sign evaluating for peripheral nerve irritation via direct percussion)
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Psychological evaluation, including signs of nonorganic pain
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