Surgical Interventions
Surgical Interventions
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Surgical strategies, including stimulation and ablative procedures, are believed to be aviable component to the therapeutic regimen to be considered in the treatment of central pain.
Unfortunately, some surgical procedures that are effective in the short term offer little in the way of long-term relief and can lead to an exacerbation of pain.
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The immediate results of surgical interventions seem to be encouraging, although the relief of pain is only transient, rarely lasting longer than a few months. Many ablative procedures have been tried, including thalamotomy and mes-encephalotomy and mesencephalic tractotomy, which have been described to be effective in 50 to 70% of patients. The evoked pain of central pain is best treated with somatosen-sory surgical interruption, whereas the steady component is more responsive to neuroaugumentative procedures. Ablation of the dorsal root entry zone (DREZ) has been used by several groups for the treatment of SCI pain. In general, this procedure has provided encouraging results for the treatment of SCI pain, especially that associated with secondary damage of spinal nerves. Falci et al recently described a refined DREZ procedure that used computer assisted recording and peripheral stimulation to identify the location of abnormal activity in the cord prior to performing the DREZ procedure. Using this approach, they achieved 100% pain relief in 84% of patients with post-SCI pain.
Surgical intervention has a definite place in the treatment of central pain after medical and other noninvasive procedures have been attempted. A major problem with the rationale for using surgical procedures is that each case of central pain may have a varied etiology and pathophysiology; therefore, it is difficult to select the right procedure. For this reason the tendency is to avoid the use of ablative or destructive procedures and to use stimulating electrodes deep in the CNS or on the spinal cord. Surgical procedures associated with central pain include anterolateral cordotomy, bulbar spinothalamic tractotomy, bulbar trigeminal tractotomy, commissural myelotomy, parietal cortectomy, destruction of thalamopanetal radiations, hemispherectomy, phalotomy pyramidio-posterior radicellotomy and thalamotomy. Another approach that as been moderately successful in producing complete or fairly good pain relief following cerebrovascular strokes is pulvinarectomy. The actual therapeutic benefits of pulvinar lesions might be due to the encroachment on the posterior thalamic region; bilateral lesions seem to alter the emotional reaction to pain and might give rise to a kind of pain agnosia. Given the reported anatomic data and repeated observations of pain recurrence at long-term follow-up after stereotaxic lesions of both the neospinothalamic and paleospinothalamic systems, it is clear that compensatory processes take place in some part of the CNS. On the assumption that reorganization of pain impulses takes place not only following unilateral extensive thalamomesencephalic lesions, but also in cases with extensive bilateral lesions. Speigel et al put forward the hypothesis that cell groups outside the thalamus and the upper mesencephalon in which pain-conducting fibers end may allow the entrance of pain into consciousness.