Pain

Pain is “an unpleasant sensory and emotional experience associated with actual or potential tissue damage.”  The International Association for the Study of Pain (IASP) also describes it as being an “individualistic, physiologic, learned and social response to a noxious stimulus.”  It is important to note that often times, incidents which are painful to one person may not be painful to another.  Likewise, certain stimuli may occasionally produce pain to an individual, may at other times produce no pain to the same individual.  Pain can often be a complicated process for the patient to understand, and a life altering issue to handle. 

In the most general of ways, pain can be divided into two main categories, Acute and Chronic.
Acute Pain
serves to warn the body that there is a present or potentially present injury.  It is usually self- limited such as pain from a pin prick.
Chronic Pain
serves no true physiologic purpose but is rather a disease unto itself.  It is the result of acute pain which has not completely resolved.
A
common type of chronic pain is that of the musculoskeletal system.  Pain here generally starts from an acute injury such as a whiplash.  If the acute injury does not resolve completely or correctly, the resultant acute pain persists and the pain becomes denoted as subacute.  That is, pain beyond the acute stage (generally 1-3 weeks), but not yet chronic.  There is no exact clinical classification on when chronic pain begins, however, it is generally construed as pain lasting longer than 6 months. The chronic pain resultant of unresolved damage to the musculoskeletal system is often caused by fibrous adhesions developed within the area of original damage.  When muscle is torn such as in a whiplash injury, muscle fibers do not grow back.  Instead, deposits of fibrous tissue fill in the torn areas.  In minute amounts, this is clinically insignificant.  In larger amounts however, these adhesions (scar tissue) incorporate within muscle fibers and layers, and causes inhibited movement.  Scar tissue is non-elastic, and thus when incorporated into the regional muscles, restricted range of motion can occur.  These adhesions also potentially cause direct stimulation to free nerve endings called C-Fibers and manifest as chronic pain.

There are a number of pain classifications within these two general categories of acute and chronic.  The various types, along with the etiology, patient history, and other variables each have different treatment and prognostic determinants. To best treat your pain, it is important to have your pain issues correctly diagnosed by your physician.

 

Basic types of Pain

Radicular Pain is a type of pain that radiates down a nerve and is secondary to a lesion compressing or irritating a nerve, such as a herniated disc compressing a nerve root.

Neuropathic Pain is a type of pain that follows the path of a nerve that is secondary to a damaged nerve, such as in diabetes.

Nociceptive Pain is pain that results from activity within neural pathways secondary to actual tissue damage or potentially tissue-damaging stimuli.

Allodynia is a condition that often occurs from chronic pain. It is a painful response to something that is not usually painful.  It is similar to light touch on a sunburned arm causing pain, where the same touch on normal skin would be painless.

Hyperalgesia is an abnormally increased response to something that is typically painful.  There are a number of causes including damage to nerves or long term opioid use among others.

Visceral pain is pain felt from organs such as gall bladder pain or that of a heart attack.

The Perception of Pain occurs through four major processes

Transduction is the process where the nerves that take messages to the brain (afferent nerves) help to figure out the type of stimulus that just occurred (e.g. sharp pain as in a pin prick or burning pain as in a hot surface.)

Transmission is the process by which the nerve signals are sent to the spinal cord and then along specific pathways to the brain.

Modulation is the process of magnifying or dulling the pain related nerve signals.  This magnifying or dulling is thought to occur in multiple locations throughout the spinal cord.

Perception is the conscious awareness of the experience of pain.  It is an individualized experience and is resultant of not only the painful stimulus, but also the individual’s past experiences, psychology, health status, medications, and numerous other variables.