Referred pain

Referred pain is felt in a part of the body different from the actual tissue causing the pain. Typically, the pain is initiated in a visceral organ or tissue and referred to an area of the body surface. Classic examples of referred pain include headache and angina. Interestingly, the brain does not contain nociceptors therefore, pain perceived as a headache originates in other tissues, such as the eyes sinuses muscles of the head and neck and meninges. Angina, or chest pain, is caused by coronary ischemia. It may be accompanied by pain referred to the neck, left shoulder, and left arm. 

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Clinical manifestation Primary hyperalgesia, allodynia, spontaneous pain Secondary hyperalgesia, allodynia, spontaneous pain, aberrantly referred pain ... 

Visceral pain involves injury to nerves on internal organs (e.g., intestines or liver) and can present as diffuse, poorly differentiated, and often referred pain. Acute pain should be treated aggressively, even before the diagnosis is established, except in conditions of head or abdominal injury where pain may assist in the differential diagnosis. 

Physical findings Right upper quadrant pain, hepatomegaly, and liver tenderness, with referred pain to the left or right shoulder (Note Erosion of liver abscesses may present as peritonitis)... 

Referred pain most likely results from the convergence of visceral and somatic afferent fibers on the same second-order neurons in the dorsal horn of the spinal cord (see Figure 8.3). Therefore, the brain has no way of identifying the original source of the pain. Because superficial inputs normally predominate over visceral inputs, higher centers may incorrectly attribute the pain to the skin instead of the deeper tissue. 

At the sensitive extreme are those who experience pain of an acute nature even when the stimulus is only moderate. Those hypersensitive individuals are perhaps those for whom even suggestion may cause pain and who exhibit referred pain in a most striking manner. A recent observation would make it appear likely that hyposensitive, average and hypersensitive individuals are about equal in number. Papper, et al., 14 state that only about one-third of a group of 286 unselected patients complained of severe postoperative pain, one-third had moderate pain, and one-third no pain at all. 

Graven-Nielsen, T., Kendall, S. A., Henrikksson, K. G., Bengtsson, M., Sorensen, J., Johnson, A., Gerdle, B., Arendt-Niesen, L. Ketamine reduces muscle pain, temporal summation, and referred pain in fibromyalgia patients, Pain 2000, 85, 483-491. 

The temporomandibular joint (jaw) can be affected, resulting in malocclusion and difficulty in chewing food. Inflammation of cartilage in the chest can lead to chest wall pain. Hip pain may occur as a result of destructive changes in the hip joint, soft-tissue inflammation (e.g., bursitis), or referred pain from nerve entrapment at the lumbar vertebrae. 

Angina pectoris strictly translated is pain in the pectoral region of the chest. Usually this is referred to simply as angina and the typical presentation is that of a crushing pain in the upper left side of the chest which may radiate into the neck or down the left arm. The pain is usually severe and often produces significant distress in the sufferer. This is referred pain that is brought about because of insufficient blood flow to the myocardium. In severe cases, it may be a symptom of acute coronary thrombosis (heart attack). 

Visceral pain is the dull and aching pain caused by stimulating nerve endings in smooth muscle or sympathetically innervated organs. Visceral pain is referred pain. This makes it difficult to localize the source of the pain. Pain of a myocardial infarction (MI) is an example of visceral pain. MI can be described as cmshing chest pain and also described as pain in the left arm or hand and even the shoulder, left back, or the left ear. Visceral pain is best treated with opioid analgesics. 

Dysuria and urinary frequency and urgency may occur if the affected colonic segment lies close to the urinary bladder, and afferent visceral nerves from the inflamed colon, by way of the sacral plexus, may carry referred pain to the scrotum or suprapubic region. 

Scar decreases the ability of the muscle to contract effectively. On ultrasound scar appears as linear or stellate echogenic tissue which is surrounded by relatively normal muscle (Fornage 2000). On dynamic examination there is loss of elasticity of the involved tissue which may appear tethered. Occasionally, this tethering may involve adjacent nerves resulting in referred pain. 

In addition to AP and lateral radiographs, the child may complain of referred pain in the wrist and increased tenderness on forearm supination/prona-tion. 

Referred pain Occurs in a region remote from the source... 

The cervical region musculature is commonly involved in stress-related reactions. During times of stress, individuals tend to tense the neck and upper back muscles, elevate the shoulders, and as a result have pain and stiffness of the neck and upper back. Some patients tend to "carry the weight of the world on their shoulders, and the trapezius tenses. Often, tender points and trigger points develop in this muscle. Trigger points in the trapezius usually refer pain to the head. Teaching the patient techniques to cope with stress is important in the treatment of stress-related somatic dysfunctions. 

Patients may experience a sudden onset of low back pain with bending or lifting an object or a more gradual onset of low back pain. The pain may radiate into a lower extremity, frequently following the course of the sciatic nerve. Depending on the nerve root involved and the severity of the herniation, there may be sensor) or reflex changes or motor weakness. Neurologic-deficit helps differentiate radiculopathy from referred pain. 

Although arm pain may be caused by some intrinsic joint or soft tissue problem, there are several extrinsic sources of arm pain that must be kept in mind, such as cervical pathology, a problem with the joint above or below the affected one, cardiac pathology, e.g., myocardial infarction or angina, pleurisy, or an irritation of the diaphragm by cholecystitis, peritonitis, or a gas bubble from laparoscopic surgery. The shoulder in particular is probably the most common site of referred pain in the body. 

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