Pain is an unpleasant feeling that is conveyed to the brain by sensory neurons. The discomfort signals actual or potential injury to the body.
However, pain is more than a sensation, or the physical awareness of pain; it also includes perception, the subjective interpretation of the discomfort. Perception gives information on the pain's location, intensity, and something about its nature. The various conscious and unconscious responses to both sensation and perception, including the emotional response, add further definition to the overall concept of pain.
The origin of some pain is neuropathic, while other pain is nociceptive. This is important to know because different treatments work better for each type of pain.
Acute Back Pain: is commonly described as a very sharp pain or a dull ache, usually felt deep in the lower part of the back, and can be more severe in one area, such as the right side, left side, centre, or the lower part of the back. Acute pain can be intermittent, but is usually constant, only ranging in severity. Sometimes, acute back pain can be caused by injury or trauma to the back, but just as often has no known cause. Patients with acute back pain, even when it's severe, will typically improve or completely recover within six to eight weeks.
A contusion, torn muscle, or strained joint resulting from a back injury can cause acute pain. Patients with any of these conditions typically exhibit pain, muscle spasms, and decreased functional activities. Treatment is short-term and usually successful. With physical therapy, follow-up treatment, and prevention practices, these patients typically return to full functionality in a few weeks. Occasionally, these patients will re-injure themselves and have to return for a short course of treatment. Patients with acute pain occurring more than three times in one year or who experience longer-lasting episodes of back pain that significantly interfere with functional activities (e.g., sleeping, sitting, standing, walking, bending, riding in or driving a car) tend to develop a chronic condition.
Acute pain can also be associated with headaches or muscle cramps. This type of pain usually goes away as the injury heals or the cause of the pain (stimulus) is removed. To understand acute pain, it is necessary to understand the nerves that support it. Nerve cells, or neurons, perform many functions in the body. Although their general purpose, providing an interface between the brain and the body, remains constant, their capabilities vary widely. Certain types of neurons are capable of transmitting a pain signal to the brain.
As a group, these pain-sensing neurons are called nociceptors, and virtually every surface and organ of the body is wired with them. The central part of these cells is located in the spine, and they send threadlike projections to every part of the body. Nociceptors are classified according to the stimulus that prompts them to transmit a pain signal. Thermoreceptive nociceptors are stimulated by temperatures that are potentially tissue damaging. Mechanoreceptive nociceptors respond to a pressure stimulus that may cause injury. Polymodal nociceptors are the most sensitive and can respond to temperature and pressure. Polymodal nociceptors also respond to chemicals released by the cells in the area from which the pain originates.
Nerve cell endings, or receptors, are at the front end of pain sensation. A stimulus at this part of the nociceptor unleashes a cascade of neurotransmitters (chemicals that transmit information within the nervous system) in the spine. Each neurotransmitter has a purpose. For example, substance P relays the pain message to nerves leading to the spinal cord and brain. These neurotransmitters may also stimulate nerves leading back to the site of the injury. This response prompts cells in the injured area to release chemicals that not only trigger an immune response, but also influence the intensity and duration of the pain.
Chronic Back Pain: is commonly described as deep, aching, dull or burning pain in one area of the back or travelling down the legs. Patients may experience numbness, tingling, burning, or a pins-and-needles type sensation in the legs. Regular daily activities may prove difficult or impossible for the chronic back pain patient. They may find it difficult or unbearable to work, for example, even when the job does not require manual labour. Chronic back pain tends to last a long time, and is not relieved by standard types of medical management. It may result from a previous injury long since healed, or it may have an ongoing cause, such as nerve damage or arthritis. Chronic pain refers to pain that persists after an injury heals, cancer pain, pain related to a persistent or degenerative disease, and long-term pain from an unidentifiable cause. It is estimated that one in three people in the United States will experience chronic pain at some point in their lives. Of these people, approximately 50 million are either partially or completely disabled. More information including fibromyalgia.
Chronic pain may be caused by the body's response to acute pain. In the presence of continued stimulation of nociceptors, changes occur within the nervous system. Changes at the molecular level are dramatic and may include alterations in genetic transcription of neurotransmitters and receptors. These changes may also occur in the absence of an identifiable cause; one of the frustrating aspects of chronic pain is that the stimulus may be unknown. For example, the stimulus cannot be identified in as many as 85% of individuals suffering lower back pain.
Other types of abnormal pain include allodynia, hyperalgesia, and phantom limb pain. These types of pain often arise from some damage to the nervous system (neuropathic). Allodynia refers to a feeling of pain in response to a normally harmless stimulus. For example, some individuals who have suffered nerve damage as a result of viral infection experience unbearable pain from just the light weight of their clothing. Hyperalgesia is somewhat related to allodynia in that the response to a painful stimulus is extreme. In this case, a mild pain stimulus, such as a pin prick, causes a maximum pain response. Phantom limb pain occurs after a limb is amputated; although an individual may be missing the limb, the nervous system continues to perceive pain originating from the area.
Mechanical Back Pain: a form of acute pain is aggravated by movement and worsened by coughing. This type of pain is usually alleviated with rest. Mechanical back pain is typical of a herniated disc or stress fracture. For patients with this condition, forward movements of the spine usually cause pain. In addition, posture, coughing, sneezing, and movement can all influence pain coming from the spine. When acute back pain is severe and travels down both legs, it could be caused by lumbar disc disease, the most common cause of true sciatica, another form of acute pain.
Neuropathic Pain: is caused by damage to nerve tissue. It is often felt as a burning or stabbing pain. One example of neuropathic pain is a "pinched nerve."
Nociceptive Pain: is caused by an injury or disease outside the nervous system. It is often an ongoing dull ache or pressure, rather than the sharper, trauma-like pain that is characteristic of neuropathic pain.
One example of nociceptive pain is arthritis pain, some people experience mixed pain, which is a combination of neuropathic and nociceptive pain.