Pain

Pain is a universally-understood sensation of discomfort, distress, or agony that results from stimulation of specialized nerve endings. It serves as a protective mechanism in that painful stimuli often coincide with tissue damage. Avoidance of pain is a powerful survival mechanism, and the motivation to avoid pain is as deep-seated as are the drives to obtain food and reproduce. It is defined by the International Association for the Study of Pain as "an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage."

Pain is the most frequent reason for seeking medical attention, and hundreds of different medicines exist for treating pain. The general term for pain-relieving medicine is analgesic, and relief of pain is also known as analgesia.

Other Names
Many specific types of pain have their own names, usually derived from the name of the affected body part and a Greek or Latin suffix denoting pain. For example, cephalgia (headache) combines the Greek words for head (cephale-) and pain (algos), and achillodynia refers to the Achilles tendon with another Greek word for pain (-odynia).

Other names for pain are specific for the type, rather than the location, of the pain. For example, allodynia refers to pain attributable to stimuli that do not usually cause pain.

Types
Pain can be described in terms of its duration, location, and intensity. It can also be classified according to the underlying cause. All of these characteristics are helpful in determining the best treatment options. Some specific examples include
 * Back pain, often due to repetitive motion or overwork, may originate in muscles of the back.
 * Pelvic pain often originates with pelvic organs such as the uterus or rectum.
 * Phantom limb pain is pain that localizes to a missing extremity; phantom pain can also be attributed to surgically removed organs such as the breast.

Diagnosis
Pain intensity is often measured with the VASPI, a scale where the patient points to a location somewhere between 0 ("no pain") and 10 ("worst pain imaginable").

Brain waves to measure pain intensity in an objective way?

Treatment
Treatment choices are guided by the intensity, location, and cause of the pain. After attempts to remove or stop the noxious stimulus, many options exist.

Nonprescription Medicines
Over-the-counter pain remedies include aspirin, ibuprofen, and acetaminophen.

Oral Prescription Medicines
More intense pain that is not adequately controlled by OTC medications can often be controlled with drugs such as morphine.

Injectable Medicines
For patients who cannot swallow or for drugs that are not absorbed from the gut, intravenous (IV) drug delivery may be a good choice. Drugs include morphine. Pain reliving medicines can also be given subcutaneously, in which case the effect remains localized to near the site of injection. Local anesthetics such as lidocaine are an example.

Nerve Blocks
Often groups of nerves are responsible for pain; the nerves may be gathered together in a group termed a ganglion or plexus. Local anesthetics can be injected near the ganglion to block transmission of painful stimuli.

Electrical Stimulation
Transcutaneous electrical nerve stimulation (TENS) is a common form of electrical stimulation used in pain management. It involves a small, battery-operated device that delivers small electrical pulses in the area of pain-transmitting neurons; the electrical signals from the TENS unit are meant to disrupt the nerves' ability to transmit pain signals to the brain.

Intrathecal Prescription Medicines
The brain and spinal cord make up the central nervous system (CNS) and are protected from the rest of the body by the blood-brain barrier (BBB). Besides protecting the CNS from the blood, the BBB also generates cerebrospinal fluid' (CSF) that surrounds the brain and spinal cord and occupies hollow chambers in the brain (the ventricles). Delivery of drugs directly into the CSF is sometimes necessary, both to avoid toxic effects of drugs on organs such as the liver and lungs and to provide a much higher local concentration of the drug. This intrathecal route of drug administration is more expensive, difficult, and potentially dangerous than oral or IV drug administration. Drugs such as morphine and ziconotide are given intrathecally.

Nonpharmacological Treatments
Some types of pain treatments do not involve drugs.

Notable Experts
Many physicians specialize in treating pain and may further focus on treating pain related to a specific location or cause, i.e., cancer pain or lower back pain. Doctors who speicalize in treating pain may also be qualified as anesthesiologists.

Organizations
The American Board of Anesthesiology (ABA) is the only organization recognized by the American Board of Medical Specialties to offer special credentials in pain medicine. The American Board of Pain Medicine offers certification in Pain Medicine to qualified physicians.

Related Videos
Steven Castellano (Student Scientist, High Technology High School) explains how acupressure can alleviate pain and increase alertness in this BigThink video "Introducing Acupressure":