Developmental neuroanatomy and neurophysiology of pain

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Developmental neuroanatomy and neurophysiology of pain

Text of Developmental neuroanatomy and neurophysiology of pain

  • 1. Article Lead Author: Fitzgerald, Maria Date: ?Article: Developmental Neuroanatomy and Neurophysiology of Pain 1. Pain felt at: a. If the article specifically asserts unborn children feel pain, at what post fertilization age? b. Page: 12, Left Column, First Paragraph. " ...there is little doubt that pain responses exist even in the youngest preterm infant." 2. Nociceptors: a. Ifthe article states nociceptors are present, at what post-fertilization age? b. Page: 12, Left Column, Second Paragraph. "The properties of the peripheral nociceptors, at birth, are analogous to those of mature nociceptors." 3. Thalamus link: a. If the article states nerves link nociceptors to the thalamus, at what post fertilization age? b. Page: 4. Subcortical plate link: a. If the article states nerves link to the subcortical plate, at what post-fertilization age? b. Page: 5. Noxious stimuli reaction: a. Does the article refer to reaction to noxious stimuli? At what post-fertilization age? b. Page : 6. Stress hormones: a. Does the article refer to increase in stress hormones with noxious stimuli? At what post-fertilization age? b. Page: 7. Long-term effects: a. Does the article describe long term harmful effects from exposure to noxious sti muli? b. Page: 8. Fetal anesthesia: a. Does the articl e refer to use of fetal anesthesia and its effect? At what post fertilization age? b. Page: 15, Left Column, Second Paragraph. "This response is a permanent one, whereby the injury results in a structural and functional reorganization of the nervous system and alters the final adult pattern of connections."
  • 2. Page: 15, Left Column, Third Paragraph, "However, in many cases, developing neural processes require particular conditions at critical times in order to develop normally."9. Cortex: a. Does the article relate to the asserted need for cortical involvement to experience pain? How? b. Page:10. OTHER a. Page: 12, Right Column, Last Paragraph. "Recent evidence has shown that the cingulated gyrus is especially important in the emotional and attentional aspect of pain and it would be interesting to know something of the development of this region."
  • 3. 2 Developmental Neuroanatomy and Neurophysiology of Pain Maria Fitzgerald K.J.S AnandAlthough the study of the developmental TIME COURSE OF PAINneurobiology of pain pathways is stili very RESPONSESnew, we are beginning to gain some insightsinto how pain responses become organized In the mid-1980s an important change tookin infancy. In this chapter our present place in the study of pain. Patrick Wall pu-:---_ _ _ _~knowledge of the structural and functional lished a paper entitled "Future Trends indevelopment of pain pathways will be re Pain Research" (2) in which he pointed outviewed . To do this effectively we have that the scientific study of pain had been redrawn on principles established in two other stricted to the instant events that follow aareas of neurobiology. The first of these is noxious stimulus, and that while thesethe general developmental processes that events were important, clinical pain often in underlie the growth and maturation of the volved much longer-term events. Pain, itnervous system. These are important be was argued, falls into different time ep cause they provide the context within which ochs-the immediate pain lasting seconds orimmature pain mechanisms are operating. minutes, the medium-term pain lastingThe second is the study of adult pain path hours or days, and the longer-term pain last ways, which are important because they ing weeks or years. Although all three ep provide an end point toward which devel ochs are important, they are not equal inoping pain pathways are heading. Research terms of human anguish. The mechanismsers interested in pediatric pain need to keep involved may be the same for each epoch,abreast of ad vances in both these areas to differing only in time course, but it is becom fully comprehend how infants and children ing increasingly evident that different mech respond to pain and to noxious stimuli. anisms are involved in longer-term acute Much of our knowledge of the basic bi and chronic pain. Now, in the early 1990sology of pain development has been ob we are becoming more aware of the ability oftained fro m studies on laboratory rats. Rats the nervous system to switch on long~nd h umans hav e different developmental lasting changes in response to certain stimuli~l me ta bles, bu t the basic sequence of events and we are increasing our research intoIn the ma tura tion of sensory systems are the such longterm responses to noxous s timuli .s am in both species. Comparative studies of (3, 4) .somatos nsory and motor developmentshow th at a lthough rats are relatively im ma ture at birth, at ap p roximately the same IMMEDIATE PAIN RESPONSEsta.ge as a hu man infan t is at 24 weeks ges A n oxious stimulus results in an immediateta tIOnal age, rats d velopment is h igh ly ac response in both the somatic and autonomiccelerated (1). For th purpose of this chap ter, nervous sys tems (Fig. 2.1A) . In ma ny casestherefore, data o bt ained from newborn rats the response is a p ro tective one, su h s therelate to prematu r human infants and data withdrawa l flexion refl x. That uch pail refrom 2- to 3- week -old rats to infants d uring ponses exi t in neonates has been a subjecttheir first year . of considerab le study (5-9). Despite some 11
  • 4. 12 / 1 Theoretical Background variability and a certain lack of spedfidty in- - very slow synaptic-ttansmission;-with-pro-- the responses resulting in difficulties in mea longed synaptic delays, rapid adaption, and surement, there is little doubt that pain re habituation for some considerable time (12, sponses exist even in the youngest pretenn 18). Furthermore, lack of local inhibitory l!:!I!:rul! infant. control produces large receptive fields and ~ activati Examination of the anatomical and phys prolonged responses during the postnatal immature n, iological development of the pathways in period (18). Thus, the after-discharge of a path.l-- - ---_ -YQI-yeg tn the~~E~e..o~~es reveals that neural dorsal nom cell is often greater than its initial elements are in place frama-neaTly Stageof -Tesponse--t~ti-m-ulus-.-.Jn..act,jhepr:o-
  • 5. 2 / Neuroanatomy a/ld Neuropllysiology of Pain / 13 Sensation Sensation -Established Pain Immediate Established Pain Response Response activation 01 activation 01 immature nociceptive long term processes pathways in immature nociceptive pathways ~ . .. Sensitization . - --;~~: :... - ._-_. _ ... . -. --_ J ,-< trvo o Altered excitability Reflexes Sensation Long Term