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Recent Advances in the Treatment of Pain

temperature perception proved by pinprick or thermal stimuli was relatively small, involving a girdle-shaped area corresponding to the level of the incision. In 10 patients he measured pain conduction time by the method of Gordon & Whitteridge (1943). He found a significantly longer conduction time for the same stimulis applied to skin below the level of incision with preserved pinprick sensation, and he suggested that the clinical results ofcommissural myelotomy were partly attributable to injury to the most medial fast conducting fibres of the dorsal funiculi. Adopting the views of Noordenbos (1959) he points out that pain is produced normally by two anatomically and functionally different systems, one anterolateral and the other dorsal. When one system is partially or completely damaged the normal afferent time and space pattern of impulses reaching the brain is distorted and the result is a loss of the normal experience of pain, although there may be a new unpleasant experience, hard to define, to which the patient can be indifferent. Recently Schvarcz (1973) has performed stereotactic myelotomy on 18 occasions. He obtained excellent results in 13 of the 17 patients, one of whom a patient with Hodgkin's disease and severe pruritus was completely relieved of pain and pruritus up to the level of the first cervical dermatome. He was not always able to demonstrate sensory losses and noted that the localization of stimulus, sharp and blunt discrimination were preserved although the stimulus itself was not painful. He noted that occasionally bizarre analgesias with unusual distribution occurred, which he attributed to interruption of decussating spinothalamic fibres. Although he suggests similarity with the effects of centre median lesions, the difference is that in thalamic cases subjective pain is removed but patients do not have analgesia. In the case ofmyelotomy both subjective complaint of pain and the objective complaint of pain disappear. To summarize, this procedure seems to be useful in avoiding the disorders associated with cordotomy and strongly suggests that the organization of pain pathways is a complex interaction between mediodorsal and anterolateral fibres. The interruption of a slow, multisynaptic pathway in or around the grey matter may also play a role in producing the curiously discrete objective responses.