Many medical illnesses and injuries present with pain. Acute pain is the body's warning system to stop using an affected body part and allow it to heal. Often it is important to treat the acute pain along with the presenting disorder. As stated in other pages on this web site, the best treatment for chronic pain is prevention. Sometimes treating the underlying disorder is adequate enough to relieve the pain. When this is not the case, or when the damage done to the body is severe enough to be accompanied by ongoing residual pain, we look at several ways to categorize and break down pain so that it can be properly treated.
Inflammatory pain occurs when the body responds to tissue damage with the release of chemicals from blood vessels, fiboroblasts and local macrophages. The pain spreads to chemical receptors around the injured area, covering a larger area than the injury itself (Hyperalgesia). Additionally a secondary response occurs when touch sensitive nerves become involved and light touch begins to cause pain (Allodynia). Finally the Central Nervous System may become involved with a process called sympathetic coupling and pain may be caused even without light touch (Sympathetically Maintained Pain).
Mechanical pain is the pain that arises from using an injured body part. An example would be moving an inflamed joint causing increased pain. If the injured body part is necessary to move constantly, this can be a major problem. An example would be the constant pain experienced by painful disc injuries in the lower back. Since the movement of the lower part of the body revolves around this area, pain can be quite severe and relentlessly constant.
Muscle spasm pain occurs when the muscle or some of the muscle fibers (Mytofascial Trigger Points) contract and do not relax. Any movement around the affected muscle may cause increased mechanical pain. Additionally the pain can be referred to other areas of the body, distant from the spasm. This spasm may be a local problem of the muscle itself, or it may represent a problem of another injured tissue, such as a spinal disc that causes the muscle to go into spasm. The pain that results from muscle spasm may be acute or chronic in nature and muscle spasm pain may cause local inflammation of the tissue that covers the muscles (Fascia).
Nerve pain may occur for several different reasons. Nerves are very sensitive and when a body part presses against them, such as in a nerve entrapment syndrome, a painful response is evoked. Additionally, nerves can be partially cut or totally severed. Although one would think that a severed nerve would not cause pain, because nerve receptors are no longer connected to the Central Nervous System, new receptors are grown at the stump of the severed nerve and these fire excessively causing more pain. Complicating the picture of nerve injury is the type of Sympathetic Nervous System coupling that can occur. When this effects a local region of the body such as an arm or leg it is called Complex Regional Pain Syndrome Type 1 (CRPS 1). This local involvement can spread to other areas and become more generalized in more advanced stages of the condition. When a nerve that feeds a specific area of the body is injured this is called a Complex Regional Pain Syndrome Type 2 (CRPS 2). Both of these syndromes may need to be treated using different modalities. Nerve pain may also cause other changes in the body causing a chain reaction that builds up increased pain. This appears to be the process at work in migraine headaches. Nerve pain may also occur from damage to multiple nerve endings in the peripheral nervous system, such as from Diabetic Peripheral Neuropathy. One important distinction to make with nerve pain is the difference between pain that is caused by nerve injury (Neurogenic Pain) and pain that is caused by permanent nerve damage (Neuropathic Pain). Although there is overlap in these two categories, it is essential to try to correct the damage in Neurogenic Pain before it becomes Neuropathic Pain.
Referred Pain is pain that is perceived in a part of the body some distance from the injury. This is most common in nerve pain, but is also observed in myofascial trigger point pain.
Central Pain is pain that is increased in the Spinal Cord or Brain (Central Nervous System). There are numerous ways that this can occur. The most common cause is at the Dorsal Horn of the Spinal Cord. Constant bombardment of this area of the Spinal Cord with pain signals can cause a phenomenon known as wind-up. This dramatically increases the pain signal sent to the brain. Problems may also occur when the Sympathetic Nerve Cells are coupled with the cells in the Dorsal Root Ganglion, causing a dramatic enhancement of pain at the injury site. The brain itself may be responsible for Central Pain. Injury to the pain responsive areas of the brain can cause a marked increase in pain perception.
Psychological Pain is a common component of all chronic pain. Ultimately the mind must perceive pain for it to be a conscious phenomenon. Rarely, there is pain that comes from a totally psychological source and is felt by the patient to arise from a physical cause (Psychogenic Pain). Much more commonly, people who experience chronically painful conditions begin to be worn down psychologically and become anxious and depressed (Pain Disorder with Mixed Physical and Psychological Features). Additionally the pain itself causes the release of certain central and peripheral chemicals that increase anxiety and depression. People with painful disabilities often find their lives under siege and this adds to the emotional responsiveness of their physical pain.
As stated above, many physical disorders present with these types of pain. Most often treating the disorder resolves the pain, but it is also important to prevent the acute pain that accompanies these disorders from becoming chronic. When pain does become chronic it is essential to evaluate the type of pain involved and treat it effectively.