The ill-advised use of nerve section and dorsal rhizotomy as definitive measures for the relief of regional pain was discussed above under “Treatment of Pain.” However, with regard to ablative procedures, the risks are great and the results can be unpredictable. Neurosurgeons, therefore, have largely abandoned the operations enumerated below. They are, however, sometimes performed for intractable pain produced by cancer.
Spinothalamic tractotomy, in which the anterior half of the spinal cord on one side is sectioned at an upper thoracic level, effectively relieves pain in the opposite leg and lower trunk but is now infrequently performed. This may be done as an open operation or as a transcutaneous procedure in which a radiofrequency lesion is produced by an electrode. The analgesia and thermoanesthesia may last a year or longer, after which the level of analgesia tends to descend and the pain tends to return. Bilateral tractotomy is also feasible but with greater risk of loss of sphincteric control and, at higher levels, of respiratory paralysis. Motor power is nearly always spared because of the position of the corticospinal tract in the posterior part of the lateral funiculus.
Pain in the arm, shoulder, and neck is more difficult to relieve surgically. High cervical transcutaneous cordotomy had been used successfully, with achievement of analgesia up to the chin. Commissural myelotomy by longitudinal incision of the anterior or posterior commissure of the spinal cord over many segments has also been performed, with variable success. Dorsal root entry zone (DREZ) lesions may temporarily relieve pain in the distribution of one or two nerve roots. Lateral medullary tractotomy is another possibility but must be carried almost to the mid-line to relieve cervical pain.
Stereotactic surgery on the thalamus for one-sided chronic pain is still used in a few centers and the results have been instructive. Lesions placed in the ventroposterior nucleus are said to diminish pain and thermal sensation over the contralateral side of the body while leaving the patient with all the misery or affective experience of pain; lesions in the intralaminar or parafascicular- centromedian nuclei relieve the painful state without altering sensation (Mark). As mentioned, because these procedures have not yielded predictable benefits to the patient, they are now seldom used. The same unpredictability pertains to cortical ablations. Patients in whom a severe depression of mood is associated with a chronic pain syndrome have been subjected to bilateral stereotactic cingulotomy or the equivalent—subcaudate tractotomy. A degree of success had been claimed for these operations but the results are difficult to evaluate. Orbito-frontal leukotomy has been discarded because of the personality change that it produces. Although not an established indication, some work has been done on stimulation of the dorsal cingulate for chronic pain and on other forms of electrical and magnetic stimulation of various brain structures.
Nonmedical Methods for the Treatment of Pain
Included under this heading are certain techniques such as biofeedback, meditation, imagery, acupuncture, spinal manipulation, as well as transcutaneous electrical stimulation. Among the most intriguing treatments for patients with complex regional pain syndrome or phantom limb pain, has been mirror therapy, in which the patient is instructed to perform movements in the painful arm while observing the unaffected arm in a mirror (Cacchio et al).