Referred pain , also called reflective pain , is a perceived pain in a location other than a painful stimulus site. An example is the case of angina pectoris caused by myocardial infarction (heart attack), where pain is often felt in the neck, shoulders, and back rather than in the chest (chest), where the injury. The International Association for Pain Study has not officially defined the term; then some authors have defined it differently.
The radiating pain is slightly different from the referred pain; for example, pain associated with myocardial infarction may be referred or radiate pain from the chest. The pain in question is when the pain is located far from or adjacent to the organ involved; for example, when a person only feels pain in the jaw or left arm, but not in the chest. The pain has been described since the late 1880s. Despite an increase in the amount of literature on the subject, the biological mechanism of pain in question is not known, although there are several hypotheses.
Video Referred pain
Characteristics
- The size of the referred pain relates to the intensity and duration of the continuous/incurable pain.
- The temporary addition is a potential mechanism for the formation of referred muscle pain.
- Central hyperexcitability is important for the level of referred pain.
- Patients with chronic musculoskeletal pain have enlarged the area of ​​pain referred to experimental stimuli. The proximal spread of referred muscular pain is seen in patients with chronic musculoskeletal pain and is very rarely seen in healthy individuals.
- Sophosphorous-modal-mode switches occur in the referenced area, which emphasizes the importance of using multimodal sensory test regimes for assessment.
- Pain is often experienced on the same side of the body as a source, but not always.
Maps Referred pain
Mechanism
There are several proposed mechanisms for referred pain. There is currently no definite consensus as to which is correct. Common visceral sensory pain fibers of the heart follow the sympathetic back to the spinal cord and have their cell bodies located in the dorsal dorsal ganglia 1-4 (5). As a general rule, in the thorax and abdomen, common afferent visceral pain fibers (GVA) follow the sympathetic fibers back into the same spinal cord segment that gives rise to preganglionic sympathetic fibers. The central nervous system (CNS) feels the pain from the heart coming from the somatic parts of the body supplied by the thoracic vertebra 1-4 (5). Classically the pain associated with myocardial infarction is located in the middle or left of the chest where the heart is actually located. The pain can spread to the left side of the jaw and to the left arm. Myocardial infarction can rarely appear as pain and this usually occurs in people with diabetes or older age. Also, the dermatomes of this region of the body wall and upper extremities have their nerve cell bodies in the same dorsal root ganglia (T1-5) and synapses in the same second-order neurons in the spinal cord segment (T1-5) as common visceral sensory fibers from the heart. CNS does not clearly distinguish whether the pain is from the wall of the body or from the viscera, but it feels the pain coming from a place on the wall of the body, ie pain in the inside, left arm/arm pain, jaw pain.
Convergent projection
This is one of the earliest theories about the problem of referred pain. This is based on the work of WA Sturge and J. Ross from 1888 and then TC Ruch in 1961. Convergent projections propose that afferent nerve fibers from the tissue converge to the same spinal neuron, and explain why the intended pain is believed to be segmented in many ways just like the spinal cord. In addition, experimental evidence suggests that when local pain (pain in the stimulation site) intensified intense pain as well.
Criticism of this model arises from its inability to explain why there is a delay between the onset of pain referred to after local pain stimulation. Experimental evidence also suggests that the referred pain is often unidirectional. For example, localized pain stimulated in the anterior tibial muscle causes pain referred to in the ventral part of the ankle; However, directed pain moving in the opposite direction has not been shown experimentally. Finally, the threshold for stimulation of local pain and stimulation of the referred pain is different, but according to this model they should both be the same.
Convergences
The facilitation of convergence was conceived in 1893 by J MacKenzie based on the ideas of Sturge and Ross. He believes that internal organs are insensitive to stimuli. Furthermore, he believes that non-nociceptive afferent input to the spinal cord creates what he calls "irritable focus". This focus causes some stimuli to be perceived as referred pain. However, his ideas did not gain widespread acceptance from critics for the termination of visceral pain.
Recently this idea has regained some credibility under the new term, central sensitization. Central sensitization occurs when neurons in the dorsal nerve of the spinal cord or brainstem become more responsive after repeated stimulation by peripheral neurons, so weaker signals may trigger them. The delay in the appearance of pain shown in laboratory experiments can be explained because of the time it takes to create central sensitization.
Axon-reflex
Axon reflexes indicate that the afferent fibers are halved before connecting to the dorsal horn. Bifurcated fibers exist in the muscles, skin, and intervertebral discs. But this particular neuron is rare and does not represent the whole body. Axon-Reflex also does not explain the delay of time before the appearance of referred pain, threshold differences to stimulate localized and referred pain, and alteration of somatosensory sensibility in the area of ​​referred pain.
Hiperexcitability
Hyperexcitability hypothesizes that the referred pain has no central mechanism. However, he said that there is one main characteristic that dominates. Experiments involving harmful stimuli and recordings of animal dorsal horns reveal that the referred pain sensation begins minutes after muscle stimulation. The pain is felt in the receptive plane some distance from the original receptive plane. According to hyperexcitability, a new receptive field is created as a result of the opening of convergent convergent afferent fibers in the dorsal horn. This signal can then be considered as referred pain.
Some characteristics are consistent with the mechanisms of referred pain, such as dependence on stimuli and time delays in the appearance of referred pain compared to local pain. However, the emergence of new receptive fields, defined as referred pain, contradicts the majority of experimental evidence from various studies including research on healthy individuals. Furthermore, the pain in question generally appears in seconds in humans compared to minutes in animal models. Some scientists attribute this to the mechanisms or downstream effects of the supraspinal pathway. Neuroimaging techniques such as PET scan or fMRI can visualize the underlying neural processing pathway responsible for future testing.
Thalamic-Convergence
The convergence of the thalamus shows that the referred pain is perceived as such by the sum of the nerve inputs in the brain, as opposed to the spinal cord, from the injury site and the referred area. Experimental evidence on the thalamus convergence is lacking. However, pain studies conducted on monkeys reveal the convergence of multiple pathways in separate cortical and subcortical neurons.
Example
Laboratory testing method
Pain is studied in a laboratory setting because of the greater amount of control that can be given. For example, the modalities, intensity, and timing of painful stimuli can be controlled more precisely. In this setting there are two main ways of referring pain learned.
Algogenic Substance
In recent years several different chemicals have been used to induce referred pain including bradykinin, P substance, capsaicin, and serotonin. However, before these substances become widespread in their use, a solution of hypertonic saline solution is used instead. Through various experiments it was determined that there were several factors that correlated with salt administration such as infusion rate, salt concentration, pressure, and amount of saline used. The mechanism by which saline induces local pain pairs and is referred to is unknown. Some researchers comment that it may be due to osmotic differences, but it is not verified.
Using electrical stimulation
Intramuscular electrical stimulation (IMES) from muscle tissue has been used in a variety of experimental and clinical settings. The advantage of using a standard IMES system such as hypertonic salts is that IMES can be switched on and off. This allows researchers to use much higher levels of control and accuracy in terms of stimulus and response measurements. This method is easier to do than the injection method because it does not require any special training on how to use it. The frequency of electric pulses can also be controlled. For most studies, a frequency of about 10 Hz is required to stimulate local pain and referred pain.
Using this method has been observed that a significantly higher stimulus force is required to get referenced pain relative to local pain. There is also a strong correlation between the intensity of the stimulus and the intensity of the referred and localized pain. It is also believed that this method led to the recruitment of larger nociceptor units resulting in spatial sums. This spatial addition results in a much larger array of signals against dorsal horns and brainstem neurons.
Use in diagnosis and clinical care
The pain caused can be an indication of nerve damage. A case study conducted on a 63-year-old man with an injury he suffered during his childhood developed symptoms of pain referred to after his face or back were touched. Even after a light touch, there was pain in his arm. The study concluded that the pain may be caused by a nerve reorganization that sensitizes the face and back region after nerve damage has occurred. Mentioned that this case is very similar to what is experienced by patients with ghost limb syndrome. This conclusion is based on experimental evidence collected by V. Ramachandran in 1993, with the difference being that the arm in pain is still attached to the body.
Orthopedic Diagnosis
From the above example one can see why understanding the referred pain can lead to a better diagnosis of various conditions and diseases. In 1981 physiotherapist Robin McKenzie described what he called centralization. He concluded that centralization occurs when the referred pain travels from a distal location to a more proximal location. Observations to support this idea are seen when the patient will bend backwards and forwards during the examination.
Studies have reported that the majority of centralized patients are able to avoid spinal surgery through isolating local pain areas. However, non-centralized patients should undergo surgery to diagnose and correct the problem. As a result of this research there has been further research into the removal of pain referred by certain body movements.
One example is the pain referred to in the calf. McKenzie points out that the referred pain will move closer to the spine when the patient bends back with full extension multiple times. More importantly, the pain generated will disappear even after the movement is stopped.
General diagnosis
As with myocardial ischemia, pain referred to certain body parts may lead to a correct local center diagnosis. Somatic mapping of referred pain and associated local centers has resulted in various topographic maps produced to help determine the location of pain based on the area to which it was referred. For example, localized pain stimulated in the esophagus is capable of producing referred pain in the upper abdomen, tilting muscles, and throat. Localized pain in the prostate may radiate pain referred to the abdomen, lower back, and calf muscles. Kidney stones can cause visceral pain in the ureter because the stone slowly enters the excretory system. This can cause enormous pain in the lower abdominal wall.
Furthermore, recent research has found that ketamine, a sedative, is able to block referred pain. The study was conducted in patients suffering from fibromyalgia, a disease characterized by joint and muscle pain and fatigue. These patients are seen specifically because of their increased sensitivity to nociceptive stimuli. Furthermore, the referred pain appears in different patterns in fibromyalgic patients compared to non-fibromyalgic patients. Often these differences manifest as differences in the area referred to pain (distal vs proximal) compared with local pain. This area is also much more exaggerated because of the increased sensitivity.
References
Source of the article : Wikipedia
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