Pain / by Thomas Lewis.

  • Lewis, Thomas, Sir, 1881-1945.
Date:
1942
Catalogue details

Licence: In copyright

Credit: Pain / by Thomas Lewis. Source: Wellcome Collection.

    119/220 (page 95)
    blistered, and the reddened areas themselves are exceedingly hypersensitive. The reason why similar hypersensitivity, or swelling of the skin, has not been observed experimentally in man or animal is very possibly due to our inability to maintain nerve stimulation sufficiently long. The erythralgic skin of cau- salgia and of herpes does not come in a matter of minutes or even of hours; it is an affair of days or of weeks. But, although a full erythralgia has not been produced experimentally so far by nerve stimulation, it is quite clear that local reddening proceed¬ ing to wheals of the skin can be brought about in certain people by stimuli descending through cutaneous nerves (Grant, Pearson, and Comeau, 72). To sum up, although the observations of Teague and Good- pasture suggest the possibility of another mechanism for zoster, the evidence still distinctly favours the idea that the skin lesions of causalgia and of zoster are the result of long-continued centrif¬ ugal nerve impulses. Differentiating Forms of Tenderness To be able to differentiate clinically between tenderness of the skin when this results from changes in the skin itself and tenderness resulting from lesions of the peripheral nerves would be important. In instances of primary change in the skin, whereby the local nerve endings are rendered hyperexcitable to stimulation, two phenomena appear. First, such skin responds painfully to warmth (40° C.); and second, rubbing the skin or stretching it produces not only immediate pain but recur¬ rent pain after an interval of many seconds. This recurrent pain lasts. In cases of “neuritis'^ in which pain and tenderness is dis¬ tributed in the territory of given limb nerves or in which tender¬ ness is known to result from pressure on given nerve roots, the tender skin behaves differently. Warmth does not precipitate pain and, though friction is painful, there is no recurrent pain. These distinguishing features seem to have practical validity and usefulness (Lewis, 131). Theoretically, however, a hard distinc¬ tion is less warranted, for, in certain forms of nerve injury or dis¬ ease (causalgia and herpes), peripheral states of the skin are set up which resemble erythralgic skin; such states certainly give the response to warmth and recurrent pain to friction.