Chronic Pain

Chronic pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, which persists longer than the course of natural healing, associated with a particular type of injury or disease process. It is usually defined as pain persisting more than 1 month beyond the resolution of an acute injury, pain persisting or recurring for more than 3 months, or pain associated with injury that is expected to continue or progress.

Signs and Symptoms
Common chronic pain complaints include headache, low back pain, cancer pain, arthritis pain, neurogenic pain (pain resulting from damage to the peripheral nerves or to the central nervous system itself), psychogenic pain (pain not due to past disease or injury or any visible sign of damage inside or outside the nervous system). As a consequence of chronic pain, many patients experience vegetative signs such as sleep disturbances, decreased appetite, weight loss, diminished libido, and constipation. Most patients with chronic pain are able to give accurate and detailed descriptions of the pain. In some populations (demented adults, very young children), however, the diagnosis of chronic pain depends on careful observation and examination. At present there is no good way to quantify pain intensity with biochemical or imaging studies.

Causes
While acute pain is a normal sensation triggered in the nervous system to alert you to possible injury and the need to take care of yourself, chronic pain is different. Chronic pain persists, and has no adaptive biologic role. Pain signals keep firing in the nervous system for weeks, months, even years. There may have been an initial mishap&mdash;a sprained back or serious infection&mdash;or there may be an ongoing cause of pain such as arthritis or cancer. Nonetheless, some people experience chronic pain in the absence of any past injury or evidence of body damage.

Diagnosis
In many cases, chronic pain is caused by an underlying disease such as cancer, and treatment of the underlying disease can completely resolve the chronic pain. If a throrough evaluation fails to pinpoint the reason for chronic pain, additional tests are not recommended. The diagnosis and evaluation of pain is based on structured interviews with the patient that include the severity, location, quality, duration, course, and timing of the pain, as well as factors that make the pain better or worse. In some situations, the patient is asked to estimate the severity of his or her pain by pointing to a spot on a 10-cm scale with numbers from 0 to 10, with 0 representing no pain and 10 representing the worst imaginable pain.

Treatment
Medications, acupuncture, local electrical stimulation, and brain stimulation, as well as surgery, are some treatments for chronic pain. Some physicians use placebos, which in some cases has resulted in a lessening or elimination of pain. More and more, physicians are recognizing the benefit of trying a course of Chiropractic care. Other treatment options include physical therapy, analgesics such as morphine, antiepileptics such as gabapentin or lamotrigine, and other drugs that alter neural activity such as capsaicin and mexiletene.

Another possible approach to drug delivery that avoids some of the adverse effects associated with oral or intravenous delivery is intrathecal therapy (IT). Intrathecal pumps can be external or implanted under the skin. The pump is typically filled with one or more drugs, which are gradually pushed through a thin tube (a catheter) which releases the drug(s) directly into the central nervous system. IT therapy is expensive and invasive, but allows continuous drug delivery to patients with otherwise untreatable pain. Medications commonly delivered this way include ziconotide, morphine, and baclofen.

Holistic and alternative treatments
Psychotherapy, relaxation and medication therapies, biofeedback, and behavior modification may also be employed to treat chronic pain.

Expected Outcome
The consequences of severe chronic pain can be devastating to patients and their families. Potential adverse outcomes include opioid dependence, depression,, and even suicide. However, persistent and coordinated efforts on the part of the patient and his or her physician(s) can often result in manageable levels of pain on a more-or-less consistent basis.

Many people with chronic pain can be helped if they understand all the causes of pain and the many and varied steps that can be taken to undo what chronic pain has done. Scientists believe that advances in neuroscience will lead to more and better treatments for chronic pain in the years to come.

Research
Clinical investigators have tested chronic pain patients and found that they often have lower-than-normal levels of endorphins in their spinal fluid. Investigations of acupuncture include wiring the needles to stimulate nerve endings electrically (electroacupuncture), which some researchers believe activates endorphin systems. Other experiments with acupuncture have shown that there are higher levels of endorphins in cerebrospinal fluid following acupuncture. Investigators are studying the effect of stress on the experience of chronic pain. Chemists are synthesizing new analgesics and discovering painkilling virtues in drugs not normally prescribed for pain.