Pain is a feeling of discomfort usually caused by damaging or especially intense stimuli. Pain is the body’s way of telling a person to remove themselves from those stimuli. It also serves as a warning to prevent further injury, especially while a previous injury is healing. Pain usually goes away quickly once the stimulus is removed, but occasionally the pain can persist after, or can even be present without any stimulus being detected. Chronic pain is a condition where the underlying system is damaged and pain is felt constantly. This can be caused by a number of factors such as cancer, arthritis or other chronic illnesses.
Different structures in the body recognize different types of pain. Nociceptive pain, or pain which is limited to the peripheral nerve fibres, has two distinct systems to sense pain, visceral and somatic. The visceral system responds to pain caused by stretching, blood restriction and inflammation. This kind of pain is typically felt as diffuse and hard to locate, and evokes physiological problems as well, causing nausea and feelings of discomfort to other parts of the body. An example of this is the pain associated with conditions like irritable bowel syndrome. The somatic pain system is split into two subsystems, the deep and superficial. Deep somatic pain is the pain felt by muscles, ligaments, bones, and other related structures. The pain is described as dull and not localized. A common example is a sprained ankle or a broken bone. Superficial somatic pain is any pain associated with the skin or other superficial systems. It is a sharp, localized pain. This type of pain is typically associated with minor cuts and bruises, or small burns.
To manage nociceptive pain, the approach is different depending on which system is affected. For somatic pain, the body will eventually heal the affected structure and the pain will disappear. For more destructive injuries like a broken bone, doctors will have to intervene and help the body fix it. Somatic pain also responds well to treatment with pain medications, making them a very good solution to chronic conditions that cause somatic pain. Visceral pain is much harder to manage. It can sometimes respond to pain medication, but often the underlying disease will have to be treated in order to alleviate the pain.
Neuropathic pain is caused by damage to the somatosensory system. It’s described as tingling pain, similar to the feeling of a limb being asleep. This type of pain is most common after a spinal injury, deep burns or strokes. It’s typically chronic and the treatment of neuropathic pain is very difficult due to the sensitivity of the affected areas. Less than 60% of treatments are able to manage neuropathic pain successfully.
Phantom pain is another type, caused completely by the brain. After a person gets a limb amputated, they may feel pain where the limb used to be, despite it not being attached anymore. This is a subset of neuropathic pain, but can feel like somatic and visceral pain. Nearly 80% of amputees will experience this, with the prevalence decreasing as time goes on. This pain does not respond to painkillers very well, but an amount of success has been achieved through putting the good limb into a box with mirrors so it looks like the individual has both limbs intact, then performing a basic motor function with that limb. This allows the brain to “release” that limb and decrease the pain present in the phantom limb.