498 



HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY I 



lion of this nucleus. Thus Orchinik ti al. (204), work- 

 ing with patients of Spiegel & VVycis in whom dorso- 

 medial thalamotomy had been done, found reduced 

 fearfulncss of emotionally charged situations of many 

 types. Yet there were "no changes in intellectual 

 functioning, as measured by a standardized test." 



Conclusion 



Despite all of the foregoing data we are still unable 

 to say what level of the brain must be attained or what 

 constellation of nuclei and fibers must be active if 

 pain is to be perceived. And not only do we not know 

 the mechanisms involved in conversion of awareness 

 of pain to the more grievous state of real suffering, 

 we are uncertain as to the site and e.xtent of lesion 

 required to preclude the appearance of suffering. 



ENDOCRINES .AND P.AIN 



The recent introduction of total hypophysectomy 

 in man as a palliative treatment for advanced cancer 

 of the breast has provided an incidental and imex- 

 pectedly great reduction in or abolition of the pain 

 in many of the patients so afflicted. Luft & Olivecrona 

 (180) saw these favorable effects in 19 of 24 women 

 in their series, and B. S. Ray has stated that his 

 results are similar. The relief of pain occurs promptly 

 after operation and is not due to cortisone since it 

 continues when the drug is stopped. It has not been 

 correlated with subsidence of tumor and has oc- 

 curred both in patients who did and in others who did 

 not give objective evidence of remission, as well as in 

 patients who had either subtotal or complete hy- 

 pophvsectomy. These obserx^ations open for considera- 

 tion the po.ssibility that endocrine potentiation of 

 nervous function is implicated in the full develop- 

 ment of pain. 



ITCHING AND TICKLING 



In addition to the various sensations under the 

 heading of pain discussed already there remain for 

 consideration 'itch' and 'tickle.' .Although the decisi\e 

 feature of the stimulus which will lead it to provoke 

 an itch is unclear, the nature of the sensation, i.e. the 

 desire to scratch, is universally understood. An 

 abundance of evidence now exists to indicate that 

 itching is closely related to cutaneous pain. In a 

 number of disorders involving a loss of pain with 



presersation of touch and proprioception, the capacity 

 to itch in the analgesic zone was long ago shown to be 

 lost (4, 266). This was fully confirmed in a recent 

 study by Arieff ?/ al. (7) i)oth in patients with radicular 

 and in those with cord lesions causing the dissociated 

 decrease or loss in appreciation of a pinprick as pain- 

 ful. Itch disappears and reappears along with pain 

 perception in the reversible states of asphyxial nerve 

 i^lock (174, 175) and of local anesthesia (227, 263). 

 Rothman (227) has also noted that the converse 

 is true, i.e. that sensitivity to pain and itching may be 

 preserved in patients in whom there were zones of 

 complete tactile anesthesia. He has also reported 

 itching independent of the sense of temperature. 

 Zotterman (315) interpreted .some of his animal 

 experimental results to indicate that peripheral af- 

 ferent impul.ses mediating itching traverse C fibers, 

 but the crucial proof was lacking, namely that the an- 

 imal tended to scratch a zone from which C fiber po- 

 tentials were arising. 



As one moves into the central nervous svstem the 

 correlation of itching with pain continues; it may be 

 followed first with the central portion of the pain 

 fibers of the primary afferent neuron. Thus operative 

 di\ision of the descending trigeminal tract in the 

 medulla oblongata \ielded complete trigeminal 

 analgesia and thermanesthesia in a patient who had 

 before operation such extreme itching that he 

 scratched out all the hair in the left anterior quadrant 

 of his scalp. Postoperatively the itching stopped and 

 the hair grew back (296, pp. 459 and 512). Likewise 

 division of pain fibers at the secondary afferent neuron 

 by section of the anterior quadrant of the cord has 

 stopped even itching of pathologically .severe origin 

 and intensity. This was first noted in Sicard & 

 Robineau's patient (^4^) and in Banzet's (14) case 

 21, each with bilateral kraurosis vulvae. Further 

 examples are mentioned by White & Sweet (296, 

 p. 261). Bickford C'^4) produced itching by puncturing 

 histamine solutions into the normal skin; a protracted 

 itch followed the use of a 1:15 dilution. In five pa- 

 tients, including one with a cordotomy whose spinal 

 lesion caused loss of pain to pin while touch was pre- 

 served, he could not evoke itching from the analgesic 

 skin. Hyndman & W'olkin (133) were likewise imable 

 to provoke itching by application of itch powder 

 (from Miuuna pruriens) to the analgesic areas after 

 cordotomy. Control areas of normal sensation did itch. 



There is one discordant observation by Taylor 

 (261). His patient with generalized bilateral itching 

 continued to have this svmptom in the analgesic zone 

 following unilateral bulbar spinothalamic tractotomy. 



