(See also Fibromyalgia.)
Chronic pain is pain that persists or recurs for > 3 mo, persists > 1 mo after resolution of an acute tissue injury, or accompanies a nonhealing lesion. Causes include chronic disorders (eg, cancer, arthritis, diabetes), injuries (eg, herniated disk, torn ligament), and many primary pain disorders (eg, neuropathic pain, fibromyalgia, chronic headache). Various drugs and psychologic treatments are used.
Unresolved, long-lasting disorders (eg, cancer, RA, herniated disk) that produce ongoing nociceptive stimuli may account completely for chronic pain. Alternatively, injury, even mild injury, may lead to long-lasting changes (sensitization) in the nervous system—from peripheral receptors to the cerebral cortex—that may produce persistent pain in the absence of ongoing nociceptive stimuli. With sensitization, discomfort that is due to a nearly resolved disorder and might otherwise be perceived as mild or trivial is instead perceived as significant pain. Psychologic factors may also amplify persistent pain. Thus, chronic pain commonly appears out of proportion to identifiable physical processes. In some cases (eg, chronic back pain after injury), the original precipitant of pain is obvious; in others (eg, chronic headache, atypical facial pain, chronic abdominal pain), the precipitant is remote or occult.
In most patients, physical processes are undeniably involved in sustaining chronic pain and are sometimes (eg, in cancer pain) the main factor. However, even in these patients, psychologic factors usually also play a role. Patients who have to continually prove that they are sick to obtain medical care, insurance coverage, or work relief may unconsciously reinforce their pain perceptions, particularly when litigation is involved. This response differs from malingering, which is conscious exaggeration of symptoms for secondary gain (eg, time off, disability payments). Various factors in the patient’s environment (eg, family members, friends) may reinforce behaviors that perpetuate chronic pain.
Chronic pain can lead to or exacerbate psychologic problems (eg, depression). Distinguishing psychologic cause from effect is often difficult.
Chronic pain often leads to vegetative signs (eg, lassitude, sleep disturbance, decreased appetite, loss of taste for food, weight loss, diminished libido, constipation), which develop gradually. Constant, unremitting pain may lead to depression and anxiety and interfere with almost all activities. Patients may become inactive, withdraw socially, and become preoccupied with physical health. Psychologic and social impairment may be severe, causing virtual lack of function.
Some patients, particularly those without a clear-cut ongoing cause, have a history of failed medical and surgical treatments, multiple (and duplicative) diagnostic tests, use of many drugs (sometimes involving abuse or addiction), and inappropriate use of health care.
A physical cause should always be sought—even if a prominent psychologic contribution to the pain is likely. Physical processes associated with the pain should be evaluated appropriately and characterized. However, once a full evaluation is done, repeating tests in the absence of new findings is not useful. The best approach is often to stop testing and focus on relieving pain and restoring function.
The effect of pain on the patient’s life should be evaluated; evaluation by an occupational therapist may be necessary. Formal psychiatric evaluation should be considered if a coexisting psychiatric disorder (eg, major depression) is suspected as cause or effect.
Specific causes should be treated. Early, aggressive treatment of acute pain is always preferable and may limit or prevent sensitization and remodeling and hence prevent progression to chronic pain.
Drugs or physical methods may be used. Psychologic and behavioral treatments are usually helpful. Many patients who have marked functional impairment or who do not respond to a reasonable attempt at management by their physician benefit from the multidisciplinary approach available at a pain clinic.
Many patients prefer to have their pain treated at home, even though an institution may offer more advanced modalities of pain management. Also, pain control may be compromised by certain practices in institutions; for example, they restrict visiting hours, use of televisions and radios (which provide useful distraction), and use of heating pads (for fear of thermal injury).
Analgesics include NSAIDs, opioids, and adjuvant analgesics (eg, antidepressants, anticonvulsants—see Treatment of Pain : Adjuvant Analgesic Drugs and Drugs for Neuropathic Pain). One or more drugs may be appropriate. Adjuvant analgesics are most commonly used for neuropathic pain. For persistent, moderate-to-severe pain that impairs function, opioids should be considered after determining the following:
When prescribing opioids for chronic pain, physicians should take several steps:
Provide education and counseling about misuse: Topics should include the risks of combining opioids with alcohol and anxiolytics, self-adjustment of dosing, and the need for safe, secure storage of drugs. Patients should also be taught how to correctly dispose of unused drugs; they should be instructed not to share opioids and to contact their physician if they experience sedation.
Evaluate patients for risk of misuse, diversion, and abuse: Risk factors include prior or current alcohol or drug abuse, a family history of alcohol or drug abuse, and a prior or current major psychiatric disorder. Presence of risk factors does not always contraindicate opioid use. However, if patients have risk factors, they should be referred to a pain management specialist, or the physician should take special precautions to deter misuse, diversion, and abuse; these measures can include prescribing only small amounts (requiring frequent visits for refills), not refilling prescriptions allegedly lost, and using urine drug screening to confirm that the prescribed opioid is being taken and not diverted to others.
Obtain informed consent, when possible, to help clarify the goals, expectations, and risks of treatment, as well as the possible use of nonopioid treatment alternatives.
Regularly reassess the extent of pain reduction, functional improvement, and adverse effects, and look for signs suggesting misuse, diversion, or abuse
As pain lessens, patients usually need help reducing use of opioids. If depression coexists with pain, antidepressants should be used.
Depending on the condition, trigger point injection, joint or spinal injections, nerve blocks, or neuraxial infusion may be appropriate.
Behavioral treatments can improve patient function, even without reducing pain. Patients should keep a diary of daily activities to pinpoint areas amenable to change. The physician should make specific recommendations for gradually increasing physical activity and social engagement. Activities should be prescribed in gradually increasing units of time; pain should not, if at all possible, be allowed to abort the commitment to greater function. When activities are increased in this way, reports of pain often decrease.
Various cognitive techniques of pain control (eg, relaxation training, distraction techniques, hypnosis, biofeedback) may be useful. Patients may be taught to use distraction by guided imagery (organized fantasy evoking calm and comfort—eg, imagining resting on a beach or lying in a hammock). Other cognitive-behavioral techniques (eg, self-hypnosis) may require training by specialists.
Behavior of family members or fellow workers that reinforces pain behavior (eg, constant inquiries about the patient’s health or insistence that the patient do no chores) should be discouraged. The physician should avoid reinforcing pain behavior, discourage maladaptive behaviors, applaud progress, and provide pain treatment while emphasizing return of function.
Nociceptive stimuli, sensitization of the nervous system, and psychologic factors can contribute to chronic pain.
Distinguishing between the psychologic causes and effects of chronic pain may be difficult.
Seek a physical cause even if psychologic factors are prominent, and always evaluate the effect of pain on the patient's life.
Treat poorly controlled pain with multimodal therapy (eg, appropriate physical, psychologic, behavioral, and interventional treatments; drugs).