Current techniques in the management of pain
The management of intractable pain has been a traditional interest of the neurosurgeon. Historically, most attempts to relieve pain involved cutting pain tracts either in peripheral nerve, sensory root, brain, or spinal cord. Such procedures, whether performed by open operation or chemical block, were based on the supposition that pain sensation could be defined anatomically and that interruption of the pain pathways could relieve pain. Thus, the anterolateral cordotomy was developed shortly after the function of the spinothalamic tract was established, and proved to be particularly useful in relieving unilateral pain of cancer. Similarly, dorsal rhizotomies and peripheral neurectomies have been used to manage many types of pain, but most successfully in the treatment of tic douloureux.
Many of these ablative procedures remain extremely useful in the management of patients with certain types of pain. Unfortunately, operations aimed at the interruption of pain tracts are not always successful in relieving pain, even though they produce analgesia. The explanation lies in the anatomy of the pain system. The classic notion of pain as a discrete entity transmitted by the spinothalamic tract is only partially correct; it appears that pain is carried by an anatomically more diffuse system. It is now thought that pain sensation is transmitted by two fiber systems.1 The first, located in the anterolateral quadrant of the cord, carries only a portion of the pain fibers. This transmits what we might call “fast” pain, the kind that one experiences following a pin prick. However, there is a second, more. . .