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Referred pain (April 2015)
Referred pain, also known as reflective pain, is pain perceived in a location other than where the painful stimulus originates. There are several proposed mechanisms to explain referred pain, with the convergence-projection theory being the most widely accepted. This theory suggests that afferent nerve fibers from different structures converge on the same spinal cord neurons, resulting in pain being perceived elsewhere. Other mechanisms like central sensitization may also play a role in referred pain. Certain organs have characteristic referred pain patterns, such as cardiac pain often radiating to the left arm, helping clinicians diagnose conditions.
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Referred pain (April 2015)
- 1. By: Kareem FisalAlnakeeb
- 2. REFERRED PAIN (REFLECTIVE PAIN ) is type of visceral pain perceived at a location other than the site of the painful stimulus. Both sites originate from the same dermatome ( embryonic segment ) so, supplied by the same dorsal root
- 3. RADIATION & REFERREDPAIN In case of ischemia brought on by a myocardial infarction (heart attack) : Classically , the pain radiate to the mid or left side of the chest , where the heart is actually located Referred pain would be when a person has pain only in their jaw or left arm, but not in the chest.
- 4. Myocardial infarction canrarely present as referred pain and this usually occurs in people with diabetes or older age
- 5. CHARACTERISTICS The sizeof referred pain is related to the intensity and duration of ongoing/evoked pain. Temporal summation (Application of several stimuli at the same site ) is a potent mechanism for generation of referred muscle pain. Patients with chronic musculoskeletal pains have enlarged referred pain areas to experimental stimuli.
- 6. MECHANISM There areSeveral neuro-physiological theories that explain mechanisms for referred pain. Currently there is no definitive consensus regarding which is correct. 1) •Convergence-projection theory 2) •Convergence-facilitation theory 3) •Axon-reflex theory 4) •Hyper-excitability theory 5) •Thalamic convergence theory
- 7. 1) CONVERGENCE-PROJECTION Thisrepresents one of the earliest theories on the subject of referred pain. This is the most acceptable explanation Suggest that: Afferent nerve fibers from diseased viscus & somatic structure converge onto the same spinal neuron CNS is accustomed to receive pain impulses from somatic structures So , cerebral cortex project pain of soma in stead of viscus
- 9. Inability toexplain why there is a delay between the onset of referred pain after local pain stimulation (pain at the site of stimulation). Experimental evidence also shows that referred pain is often unidirectional. CRITICISM OF THIS MODEL
- 10. 2) CONVERGENCE-FACILITATION suggeststhat : internal organs were insensitive to stimuli. non-nociceptive afferent inputs to the spinal cord … " irritable focus ". This focus caused some stimuli to be perceived as referred pain. its dismissal of visceral pain. CRITICISM OF THIS MODEL
- 12. Recently thisidea has regained some credibility under a new term, central sensitization. Central sensitization occurs when : neurons in the spinal cord's dorsal horn or brainstem become more responsive after repeated stimulation by peripheral neurons, so that weaker signals can trigger them. The delay in appearance of referred pain shown in laboratory experiments can be explained due to the time required to create the central sensitization.
- 13. 3) AXON-REFLEX suggeststhat : the afferent fiber is bifurcated before connecting to the dorsal horn. Bifurcated fibers do exist in muscle, skin, and intervertebral discs. Yet these particular neurons are rare and are not representative of the whole body.
- 14. Axon-Reflex alsodoes not explain : - the time delay before the appearance of referred pain, - threshold differences for stimulating local and referred pain, CRITICISM OF THIS MODEL
- 15. 4) HYPER-EXCITABILITY Experimentsrevealed that referred pain sensations began minutes after muscle stimulation. Pain was felt in a receptive field that was some distance away from the original receptive field. new receptive fields are created as a result of the opening of latent convergent afferent fibers in the dorsal horn This signal could then be perceived as referred pain
- 16. 5) THALAMIC-CONVERGENCE suggeststhat referred pain is perceived as such due to the summation of neural inputs in the brain, as opposed to the spinal cord, from the injured area and the referred area. Experimental evidence on thalamic convergence is lacking. However, pain studies performed on monkeys revealed several pathways converging on both subcortical and cortical neurons.
- 17. REFERRED PAIN MAP Upper chest/left limb : Myocardial ischaemia Head : Ice-cream headache = brain freeze ( because of the rapid cooling and rewarming of the capillaries in the sinuses ) Phantom limb pain : in amputees & quadriplegics. (sensation of pain from a limb that has been lost or from which a person no longer receives physical signals)
- 18. Right tipof scapula : Liver , gallbladder Left shoulder : Thoracic diaphragm , Spleen , lung Back : Pancreas Palm of Hand : Palmaris longus (problem originating in the forearm )
- 19. Site of referredpainDisease * always starts and felt in the skin area surrounding the umbilicus *later on localized to the right iliac fossa when the peritoneal covering is involved. Appendicitis pain *usually felt in , the retrosternal region, base of the left side of the neck, inner side of the arm, fore-arm, or even in little finger. *It may be felt in the epigastric region. Cardiac pain * usually referred to the epigatric region, * may be the right shoulder & neck. Gall bladder pain * usually referred to back behind the kidney * may be referred to the anterior abdominal wall near the inguinal region. Renal and ureteric pain * usually felt in lower neck and midline chest region.esophageal pain * usually referred to the epigastric region in the wall of the abdomen. Gastric pain