The definition of pain according to the International Association for the Study of Pain (IASP) is an uncomfortable sensory or emotional experience that a person feels in relation to actual or potential tissue damage. Pain is a very personal feeling. There is no method to objectively measure the pain a person feels. If the person says that he/she is in pain, he/she is considered to have pain. Sometimes the cause of the pain may be obvious, such as a nail stabbing in the foot, and in some cases, the cause of the pain cannot be found despite all known examinations and tests. There are various scientific theories about the physiopathological basis of pain, but it has not yet been successful to explain all pain perception. Pain sensation occurs in different layers in the peripheral nerves, spinal cord and brain.
It is necessary to determine the mechanism by which the felt pain occurs in order to choose the most appropriate treatment. Three main mechanisms have been defined as nociceptive, peripheral neuropathic pain and central neuropathic pain. There are various objective and subjective evaluation methods to understand the type of pain in the person. As a result of the doctor’s evaluation, the type of pain is determined and the treatments are shaped accordingly.
Apart from its physiological mechanism, pain is also affected by psychological, social, behavioral, environmental and occupational conditions. For example, stress in business life can increase or decrease a person’s sensitivity to pain.
Nociceptive pain occurs as a result of the response of peripheral nerve endings to painful chemical (inflammatory), mechanical or ischemic (due to oxygen deficiency) stimuli. Joint calcification pain, pain due to infection, pain due to circulatory disorder are in this group.
In nociceptive pain, clear factors that increase and decrease the pain proportionally mechanically or anatomically can be determined. Pain is of intensity proportional to the trauma, inflammation or ischemic process in question. The location of the pain is consistent with the damage caused (it can also be referred pain). The pain subsides rapidly in line with the healing process. It responds to simple painkillers (acetaminophen, non-steroidal anti-inflammatory drugs). It usually increases with movement or provocative maneuvers, has an intermittent exacerbation nature, may be felt as aching or blunt pain at rest. The person can change their posture and movements to reduce pain. Neurological symptoms such as loss of muscle strength, loss of sensation, and reflex changes do not occur. It is not associated with psychosocial factors (negative emotions).
Peripheral Neuropathic Pain
Peripheral neuropathic pain occurs as a result of damage or functional impairment in the peripheral nervous system. It is associated with various pathophysiological changes in nerve functions. There is an abnormal response of the nerve to hyperexcitability, touch, heat, chemical stimuli.
Pain due to causes such as nerve compression, nerve ending inflammation is in this group.
Pain is described as burning, stinging, tingling, electric shock. He has a history of nerve injury. Neurological complaints such as loss of feeling and potency may accompany. The spread of pain is compatible with the extension of the nerves, that is, there is dermatomal or cutaneous spread. It has little response to simple painkillers. It responds better to drugs from the antiepileptic or antidepressant group. Pain increases with movements that increase nerve pressure or stretch the nerve. The pain may spontaneously intensify and subside suddenly. Sleep disturbance may occur with increased pain at night. It can affect a person’s psychology.
There may be findings such as hyperalgesia (extreme sensitivity to pain), allodynia (stimulations that should not normally cause pain cause pain) in regions of pain distribution. Nerve damage can be demonstrated with techniques such as EMG, MRI, CT. There may be sweating, hair growth, changes in skin and nail tissue called trophic changes due to autonomic dysfunction.
Central pain is caused by damage to the central nervous system or a functional disorder. Pain is not affected by mechanical causes. It can increase or decrease in an unpredictable pattern.
Some of the pain in spinal cord injury, stroke , brain injury, Parkinson’s disease is central pain. Fibromyalgia, tension-type headache, and some of the low back pain of unknown origin may be of central origin.
Pain persists for periods beyond the expected tissue healing time. It is disproportionate to the injury or damage involved. Pain distribution may be wide, does not match the distribution of nerve fibers. There may be unsuccessful surgeries and medical treatments in the person’s history. It is associated with psychosocial factors that develop as a result of maladaptation. It is unresponsive to simple painkillers or may respond better to antiepileptic and antidepressant drugs. It causes a high degree of functional limitation. Night pain is seen, it causes sleep disturbance. The pain can be very severe, easily triggered but more difficult to subside. Symptoms of autonomic nervous system dysfunction may accompany. There is a disease or condition that affects the central nervous system.
Symptoms of hyperalgesia and allodynia may be seen. There are no signs of tissue damage.
Central pain and peripheral neuropathic findings are similar. The most important difference is the location of the problem in the nervous system.