Definition

Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage [1]. Chronic pain is a pain status that persists beyond a reasonable expected healing period for the involved tissue. It is chronic if it persists for 6 months or more despite active treatment. It is called a syndrome because a constellation of symptoms develops in those patients facing chronic pain. The most common conditions leading to chronic pain syndrome (CPS) include headaches, repetitive stress injuries, back pain, whiplash injury, degenerative joint disorders, cancer, complex regional pain syndrome, shingles, fibromyalgia, neuropathy, central pain, and multiple surgeries [2]. In excess of 50 million Americans suffer from CPS and have a degree of impairment or disability from this condition [2]. Pain disorders cost $100 billion annually in lost work days, medical expenses, and other benefit costs [2]. Chronic pain is often a hidden problem and may be an issue that individuals are reluctant to share with family or friends. This may have an impact on the awareness of CPS in the community at large.

Chronic pain is prevalent in both adults and the pediatric population. Children suffering from chronic pain frequently continue to suffer from chronic pain as adolescents and young adults [3]. Some authors have reported a higher prevalence of CPS in individuals with a history of childhood abuse and personality disorder (borderline, narcissistic) [4]. CPS is more prevalent in women and by up to twofold in some diagnoses (e.g., fibromyalgia) [5,6]. Studies suggest a relationship between chronic pain and race as well as socioeconomic status. In a study of 3730 adults between ages 18 and 49, African Americans appear to have significantly more pain and disability and live in lower socioeconomic neighborhoods [7]. Living in a lower socioeconomic status neighborhood was associated with increased sensory, affective, pain-related disability and mood disorders [7].

Given its unclear pathophysiology and the lack of a definitive diagnostic test or successful treatment, CPS imposes a challenge to health care providers. Most patients are often unsatisfied with the treatment outcomes, leading to psychosocial stress, chronic pain behaviors, medication seeking, impairment, activity restriction, limited participation, and disability.

Symptoms

The primary symptom is a protracted pain that is out of proportion to the objective pathophysiologic process. Table 97.1 shows a list of common associated symptoms. Pain may be localized to a body segment, or it could be widespread. The measurement of pain severity is subjective and typically relies on the patient’s report as well as on functional ability (work, activities of daily living, hobbies). The numeric (0-10) or the visual analogue scale that is used to assess pain often does not properly reflect the pain intensity, and despite adjustments to medical management, the reported pain level is unchanged. Because of this, clinicians may focus on functional gains as a measure of treatment success rather than on the patient’s report of a decreased numeric or visual analogue scale score.

In CPS, there are often associated pain behaviors that help establish the diagnosis. Pain behaviors include assuming poor posture, abnormal gait (limping), facial grimacing, stiff movements, and use of assistive devices that have not been medically prescribed (canes, wheelchairs, and electric scooters). Decreasing pain behavior decreases the experience of pain. Behavioral treatments are a key component of multidisciplinary pain programs and can be effective for the relief of pain.

Mood and affect disorders including depression, anxiety, emotional instability, and anger are commonly associated symptoms in patients with CPS [8]. Some studies have reported up to fourfold increased depression in patients with chronic back pain [9]. Chronicity of the pain, lack of clear etiology, and poor treatment outcomes contribute to the emotional aspect of this disorder. Just treating pain with medications without addressing the psychosocial component will lead to poor outcomes and further suffering. Part of the reasonable success associated with the multidisciplinary pain programs is related to management of the psychosocial component of the chronic pain.

Sleep disorders are prevalent in patients with CPS. Studies have shown that severity of insomnia contributes to the prediction of pain severity [10]. The insomnia associated with chronic pain needs to be anticipated and treated. Sleep-inducing medications often combined with cognitive-behavioral therapy can help improve insomnia. Sleep education, cognitive control and psychotherapy, sleep restriction, remaining passively awake, stimulus control therapy, sleep hygiene, relaxation training, and biofeedback are part of the cognitive-behavioral approach to treatment of insomnia [11]. Clinicians should be aware of increased cognitive impairment in elderly patients treated with medications for insomnia. This may lead to falls, injury, and increased pain [12].

Physical Examination

Physical examination is directed toward finding treatable causes of CPS. One of the most important parts of the physical examination is to observe the patient’s gait, body motion, posture, and facial expression as well as abnormal pain behaviors. A systematic and detailed musculoskeletal and neurologic examination needs to be conducted. If the CPS follows an injury, focused examination of the injured body part is needed. Give-away weakness, nonmyotomal weakness, and nondermatomal numbness are often encountered on physical examination. If it is done repeatedly, there are likely to be inconsistencies in physical examination findings of a patient with CPS. Redirecting the patient’s attention while repeating the examination may alter the findings and can point to pain behaviors. For example, diffuse tender points may not be tender if the patient’s focus is diverted. Another example is a negative result of the seated straight-leg test (patients are less knowledgeable about it) versus a positive result of the supine straight-leg test in the same patient.

There are diagnosis-specific examination findings that may be noted, such as allodynia and trophic changes. These may be found in the area of the initial injury or in a different body part. Depending on the complaint, examination of other systems, including gastrointestinal, urologic, and pelvic girdle, may be indicated.

Functional Limitations

Typically, there is a disproportionate loss of function in patients with CPS when it is matched to the injury and the stated age. Fear-avoidance behavior will result in deconditioning and decline in function with activities of daily living [13]. Deconditioning leads to increased perception of pain, reduced quality of life, and further psychosocial stress and disability. If such abnormal pain behavior is reinforced by health care providers or the patient’s family, it will result in chronicity of the pain and further decline in function.

Diagnostic Studies

In CPS, diagnostic studies are performed to find treatable causes that can lead to lingering pain. The results of such studies are often inconclusive or normal. Diagnostic testing may include laboratory work, electrodiagnostics, and imaging. Unless the presenting symptoms have changed, repeating costly diagnostic tests is of no value. Equally important is psychological testing. The Minnesota Multiphasic Personality Inventory is the most common psychological test used in patients with chronic pain and has been shown to help understand pain behaviors and the psychological impact on individuals with chronic pain [14] (Table 97.2).

The initial treatment focuses on management of the pain and improvement in function. Numerous studies suggest a multidisciplinary approach for management of CPS [15]. These studies show that multidisciplinary treatments of chronic pain are superior to single-discipline treatments, such as medications or physical therapy. A team approach focuses on supporting patients in reaching individual goals. Goals should be improving pain and a better quality of life by means of enhancing physical and psychosocial function. The beneficial effect of multidisciplinary treatment is not limited to improvements in pain but also extend to variables such as return to work and use of the health care resources. An anesthesiologist, John J. Bonica, was the first to appreciate the need for a multidisciplinary approach to chronic pain [16]. Members of a multidisciplinary pain management team include a pain medicine specialist, mental health specialists, a physical therapist, an occupational therapist, the primary care provider, and the patient. Ideally, the rehabilitation component is 2 to 3 hours per day, 3 days per week, for several weeks [17]. In addition, patients will see mental health counselors weekly and are monitored by the pain specialist who is overseeing the entire care.

Education of the Patient

It is crucial for the patients dealing with CPS to be educated in the complexity of the disorder and possible factors affecting its management. Patients should be knowledgeable about their participation in the treatment plan. Both patient and family should have a good understanding of the multifactorial nature of chronic pain and the benefits of multidisciplinary management. Education of the patient should be done by all members of the treatment team.

Mental Health Treatment

Psychological interventions help patients find ways to accept the condition and to adjust to it. The focus of mental health counseling is to work on pain behaviors and to educate patients about the adverse consequences of this atypical behavior. Patients need to understand that negative thoughts stemming from pain will influence mood, behavior, sleep, and chronicity of the pain. Individual or group treatment may include biofeedback, relaxation training, coping mechanisms, clinical hypnosis, and cognitive therapy techniques [18]. These options may result in improved ability to manage pain. Advanced psychological or psychiatric treatments may include pharmacologic interventions to address emotional problems, affect disorders, anxiety disorders, sleep disturbances, and panic attacks. Common medications to treat psychological disorders in CPS are listed in Table 97.3. If opioid medications are being considered for treatment of CPS, a consultation with a pain psychologist is indicated to determine risk of future abuse.

Medications

In CPS, pain medications and adjunct medication are often not able to eliminate pain, but the analgesic effect may lead to increased function, improved rehabilitation outcomes, restored sleep, and enhanced mood. Commonly used pain medications and adjunct pharmaceutical substances in CPS are listed in Table 97.4. Pain medicine specialists should evaluate the patient, prescribe appropriate medications, monitor use and effect, and make adjustments when necessary. Short-term use of medications for pain is rarely worrisome, but prolonged use may increase the possibility of adverse reactions, including gastrointestinal side effects, cognitive and memory deficits, and gait instability. Use of opioid analgesics for chronic pain, although controversial, is fairly common. Opioid analgesics must be used with utmost caution and with understanding of the challenges related to chronic opioid management as well as the social stigma attached to them. The author recommends an opioid contract and involvement of the primary care physician in decision-making. Frequent and random blood or urine drug testing (for narcotic and illicit drugs), pill counts, opioid rotation, and routine reevaluation are needed to ensure safe use and effective treatment. Currently available evidence suggests that cannabis treatment is moderately efficacious for certain types of chronic pain (e.g., neuropathic, multiple sclerosis), but beneficial effects may be offset by potentially serious harms [19,20]. Smoked cannabis reduces pain, improves mood, and helps sleep in such patients [20]. More evidence from larger, well-designed trials is needed to clarify the true balance of benefits and harms.

Rehabilitation

Both outpatient and inpatient models of care are available to manage chronic pain, although it is difficult to obtain insurance coverage for inpatient care. This population of patients starts from a lower functional level, so the duration of treatment could be longer than the average for musculoskeletal pain issues. The rehabilitation team (physical therapist, occupational therapist, recreation therapist) will work with the patient to establish a structured day including supervised exercises. The basic exercise structure will include conditioning, stretching activities, progressive core and generalized strengthening, and aerobic exercise training. Aerobic exercise can be performed in an aquatic environment. The focus will also be on correction of body mechanics, proper posture, restoration of function, modification of maladaptive behaviors, and provision of pain relief by incorporation of modalities (heat, ice, and ultrasound) and relaxation techniques [21]. Deep tissue massage, myofascial release, transcutaneous electrical nerve stimulation, Pilates, Tai Chi, and yoga are additional treatments offered to patients with chronic pain. The accumulating evidence from recent reviews suggests that acupuncture is more than a placebo for commonly occurring chronic pain conditions [22]. Manipulative therapy, within the context of interdisciplinary treatment, has been shown to be an efficient and effective treatment to improve pain and function in patients with mechanical or compressive pain [23]. Transcutaneous electrical nerve stimulation units help relieve pain and foster independence in patients with chronic pain [21].

A recreational therapist examines previous interests of the patient and barriers to return to leisure activities. Within a formal program, recreational therapists evaluate and plan leisure activities that serve to promote mental and physical health. The challenge for the rehabilitation team remains the fear-avoidance behavior.

Procedures

Depending on the pain generator, specific procedures may help patients with CPS. This is especially true if previous medical care has insufficiently addressed the symptoms. Procedures that may be effective include neuraxial blocks, facet injections, radiofrequency neurotomy, sacroiliac injection, peripheral joint injections, peripheral nerve blocks, acupuncture, trigger point injections, and infiltration of inflamed bursa or tendons. Image guidance will enhance the accuracy of spine injections and will lead to improved outcome [24,25]. Chronic pain of complex regional pain syndrome (see Chapter 99) may be addressed with neuromodulation by spinal or peripheral nerve stimulator implantation. Implantable pain pumps are indicated in pain associated with terminal cancer but may also have limited indication in difficult to control pain of noncancer origin. When relative pain relief is achieved with procedures, tapering pain medications as well as increasing intensity of the rehabilitation program is encouraged.

Surgery

There is a limited indication for surgery in chronic pain. If the pain generator is identifiable and modern surgical methods are available to treat it, surgery may be considered. Patients suffering from chronic discogenic low back pain may benefit from interbody fusion or disc arthroplasty. Patients with end-stage degenerative joint disease suffering from chronic pain would likely benefit from arthroplasty. When it is clinically indicated and other noninvasive treatments have failed to help, an intrathecal drug delivery system and spinal or peripheral nerve stimulators could be considered, both of which require surgical implantation. It is possible that despite a surgical solution, the patient will continue to suffer from chronic pain.

Potential Disease Complications

Significant disability secondary to pain as well as suicidal ideation or attempt (secondary to psychosocial comorbidities) may complicate the clinical picture.

Potential Treatment Complications

Medications used to treat chronic pain can result in class-specific side effects. Nonsteroidal anti-inflammatory drugs commonly have gastrointestinal and renal side effects. Muscle relaxants, serotonin-norepinephrine reuptake inhibitors, anxiolytics, and tricyclics can cause central nervous system suppression. Narcotics can result in nausea, constipation, respiratory suppression, mental status changes, and suppressed endogenous opioids; dependency, tolerance, and abuse may also develop. Rehabilitation program intensity that is disproportionate to the functional status of the patient may lead to dissatisfaction and poor compliance and can worsen fear-avoidance behavior. Interventions and surgical care have their specific potential complications.

Acknowledgment

The author would like to thank resident physician Tony George for his valuable time and assistance in gathering updated literature on chronic pain syndrome.