CHAPTER XIX 



Pain 



WILLIAM H. SWEET j Department oj Surgery, Harvard Medical School, Boston, Massachusetts 



CHAPTER C:ONTENT,S 



Pain as a Sensation with Its Own Peripheral and Central 



Nervous Apparatus 

 Stimulus, Sensation, and Their Measurement 



Mechanical Stimuli 



Correlation with Tissue Damage 



Heat 



Electricity 



Distention of Viscera 



Arterial Constriction with Ischemia and Arterial Dilatation 



Inflammation 



Quantitation of Severity of Pain 

 Animal Versus Human Subjects in Pain Studies 

 End Organs for Pain 



Normal Skin 



Cornea 



Abnormal Skin 



Special Cutaneous Sensory Endings 



Deeper Somatic and Visceral Receptors 

 Terminal Sensory Plexuses 

 Peripheral Sensory Nerve Fibers 



Single Fiber Studies 



Fiber Diameters and Pain Conduction 



Double Pain Responses or Second Pain 

 Pain in Abnormal Anatomical States at Periphery 



Division of Cutaneous Nerves 



Hyperalgesic State After Trauma 

 Chemical Excitants of Pain 

 Posterior and Anterior Roots 

 Pain and Autonomic Nervous System 



Sympathetic Nerv^es 



Parasympathetic Nerves 

 Spinal Cord 

 Medulla Oblongata 

 Mesencephalon 

 Thalamus 

 Cerebral Hemispheres 



Stimulation 



Lesions 



Evoked Potentials 



Second Sensory Area in Man 



Reaction to Pain 

 Indifference to pain 



Pain asymbolia 



Reactions after operations on frontal lobes 

 Conclusion 

 Endocrines and Pain 

 Itching and Tickling 

 Pain and Inhibition 

 Referred Pain 



THE NATURE AND RANGE of the sensations covered lay 

 the word ' pain' elude precise definition. Aristotle (8) 

 equated pain with unpleasantness whether arising 

 from outside the body, within the body or within the 

 ' soul' (as when one feels miserable). ' Pain or un- 

 pleasantness' stood for him as the opposite to 'pleasure' 

 and he considered every action to be "accompanied 

 by pleasure and pain." For Spinoza (65) pain was a 

 focal form of sorrow which he called one of the three 

 primary emotions. Pain, which he thought of as the 

 emotion opposite to "pleasurable excitment," he 

 "related to a man when one of his parts is affected 

 more than the others; melancholy, on the other hand, 

 when all parts are equally afl^'ected." As scientists now 

 tend to u.se the word, ' pain' contains the Spinozistic 

 implication that the unpleasant feeling is specifically 

 referred to some place or places in the body. In any 

 case it is this more localized kind of pain which is 

 more amenable to physiologic study in contradis- 

 tinction to diffuse states of unpleasantness. 



But from the standpoint of the physician it is neces- 

 sary to analyze and treat every type of disagreeable 

 feeling of which people complain. It matters not 

 whether the individual tags it by the label 'pain'. Thus 

 in the area of the face which has undergone trigeminal 

 denervation about 5 per cent of the patients have 

 severe annoying sensations which they may call 

 aches, but often they are at a loss for words to describe 



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