Understanding Pain

By Drs. David Niesel and Norbert Herzog, Medical Discovery News

Pain is so common, one in three Americans report experiencing it daily. The financial cost due to pain tops more than half a trillion dollars per year. In its most elemental form, pain is our body's way of letting us know that something is not right.

Not surprisingly, all pain is not the same. The perception of pain is quite individualized, as everyone has a different pain scale that can vary due to factors such as gender and age. It is nearly impossible to objectively measure pain -- it is one of those things that people experience differently and it is completely self-reported, so the experience is personal and the scale of intensity is individualized.

On the most basic level, pain can be classified as two types: acute (short-term) or chronic (long-term). Acute pain results mostly from injury to our tissues due to trauma, inflammation or disease. In most cases, this type of pain is self-limiting and can be easily localized, diagnosed, and treated. In some cases, acute pain can lead to chronic pain. In contrast, chronic pain is present over an extended period of time and is more difficult to treat. This type of pain can be made worse by environmental and psychological factors.

Pain can also be classified into different categories. Something called nociceptive pain occurs when specific receptors on cells are activated. This can be in response to temperature, vibration, stretching, or chemical signals released from damaged cells. This type of pain can be somatic, meaning it's associated with musculoskeletal elements of the body like skin, muscles, and bones. Somatic pain is localized and can be distinguished by the ability to activate the pain by touch or movement. There is another type of nociceptive pain called visceral. As the term implies, it involves our internal organs like the kidneys, liver, or gastrointestinal tract. Visceral pain is harder to localize and is usually described as more of an ache. Intestinal cramps are an example of this type of pain.

The other large category of pain is referred to as non-nociceptive. Non-nociceptive pain does not require the action of specific receptors. The source of this pain can be the nervous system directly. Non-nociceptive pain can originate in the pathway between a specific tissue and the spinal cord, such as the pain from a shingles infection. Alternatively, this pain can occur farther along the pathway, between the spinal cord and the brain, such as the pain of a slipped disc. The other type of non-nociceptive pain is called sympathetic pain. In this case, a damaged nerve becomes unstable and fires randomly, which is interpreted by the body as pain. This can occur after a tissue injury or a bone fracture.

The ways we experience pain is an area of research that continues to be under intense investigation. New therapies for pain management involve blocking pain signals from becoming amplified by the nervous system or devising drugs that block specific points along the pain pathway. Look for exciting new developments in this important part of neuroscience research in the future.

Medical Discovery News is hosted by professors Norbert Herzog at Quinnipiac University, and David Niesel of the University of Texas Medical Branch. Learn more at www.medicaldiscoverynews.com.