Understanding how pain is defined is important in order to learn how to better control it. For the purposes of research and medical practice, pain can be separated into three categories:
•    Acute pain
•    Chronic pain
•    Neuropathic pain

Acute Pain
One common type of pain is acute pain, currently defined as pain lasting less than 3 to 6 months, or pain that is directly related to tissue damage. This is the kind of pain that is experienced from a paper cut or needle prick. Other examples of acute pain include:

•    Touching a hot stove or iron. This pain will cause a fast, immediate, intense pain with an almost simultaneous withdrawal of the body part that is being burned. More of an aching pain might be experience a few seconds after the initial pain and withdrawal.
•    Smashing one’s finger with a hammer. This pain is similar to that of touching a hot stove in that there is immediate pain, withdrawal and then “slower” aching pain.
•    Labor pains. The pain during childbirth is acute and the cause is certainly identifiable.

The longer pain goes on the more susceptible it is to other influences and developing into a chronic pain problem. These influences include such things as the ongoing pain signal input to the nervous system even without tissue damage, lack of exercise (physical deconditioning), a person’s thoughts about the pain, as well as emotional states such as depression and anxiety.

Chronic Pain
There are at least two different types of chronic pain problems – chronic pain due to an identifiable pain generator (e.g. an injury), and chronic pain with no identifiable pain generator (e.g. the injury has healed).

Chronic pain due to an identifiable pain generator
This type of chronic pain is due to a clearly identifiable cause. Certain structural spine conditions (for example, degenerative disc disease, spinal stenosis and spondylolisthesis) can cause ongoing pain until successfully treated. These conditions are due to a diagnosable anatomical problem.

If the pain caused by these types of conditions has not subsided after a few weeks or months of conservative (nonoperative) treatments, then spine surgery may usually be considered as a treatment option.

Chronic pain with no identifiable pain generator
This type of pain continues beyond the point of tissue healing and there is no clearly identifiable pain generator that explains the pain. It is often termed “chronic benign pain”.

It appears that pain can set up a pathway in the nervous system and, in some cases, this becomes the problem in and of itself. In chronic pain the nervous system may be sending a pain signal even though there is no ongoing tissue damage. The nervous system itself misfires and creates the pain. In such cases, the pain is the disease rather than a symptom of an injury.

The term “chronic pain” is generally used to describe pain that lasts more than three to six months, or beyond the point of tissue healing. Chronic pain is usually less directly related to identifiable tissue damage and structural problems. Examples of chronic pain are: chronic back pain without a clearly determined cause, failed back surgery syndrome (continued pain after the surgery has completed healed), and fibromyalgia.

Chronic pain is influenced by many factors, such as ongoing pain signal input to the nervous system even without tissue damage, physical deconditioning due to lack of exercise, a person’s thoughts about the pain, as well as emotional states such as depression and anxiety. Chronic pain is much less well understood than acute pain.

Neuropathic Pain
Neuropathic pain has only been investigated relatively recently. In most types of neuropathic pain, all signs of the original injury are usually gone and the pain that one feels is unrelated to an observable injury or condition. With this type of pain, certain nerves continue to send pain messages to the brain even though there is no ongoing tissue damage.

Neuropathic pain (also called nerve pain or neuropathy) is very different from pain caused by an underlying injury. While it is not completely understood, it is thought that injury to the sensory or motor nerves in the peripheral nervous system can potentially cause neuropathy. Neuropathic pain could be placed in the chronic pain category but it has a different feel then chronic pain of a musculoskeletal nature.

Neuropathic pain feels different than musculoskeletal pain and is often described with the following terms: severe, sharp, lancinating, lightning-like, stabbing, burning, cold, and/or ongoing numbness, tingling or weakness. It may be felt traveling along the nerve path from the spine down to the arms/hands or legs/feet. It’s important to understand neuropathic pain because it has very different treatment options from other types of back pain. For example, opioids (such as morphine) and NSAIDs (such as ibuprofen, COX-2 inhibitors) are usually not effective in relieving neuropathic pain. Treatments for neuropathic pain include certain medications, nerve “block” injections, and a variety of interventions generally used for chronic pain.

Source: www.spine-health.com