A surgical procedure formerly used to alleviate severe intractable pain in cance

Question

A surgical procedure formerly used to alleviate severe intractable pain in cancer patients is called an anterolateral cordotomy. When performed properly, this procedure cuts the axons contained in the lateral spinothalamic tract. If the severe pain is located in the left leg, where in the spinal cord should the cut be made? (i.e., at what level in the spinal cord and on what side of the spinal cord relative to the location of the pain?). If performed properly, will the patient retain voluntary control of his/her leg muscles?

Explanation / Answer

Cordotomy is an effective procedure for relieving intractable pain and has been used to treat patients with unilateral pain of the lower body and lower extremities. Formerly, cordotomy was performed as an open surgical procedure. Conventional percutaneous cordotomy with x-ray visualization, a much less invasive procedure, allowed safe unilateral operations at the high cervical level. On the other hand, bilateral lesions high in the cervical spinal cord involving the anterior portion of the lateral spinothalamic tract have been associated with sleep-induced apnea due to bilateral destruction of the ventrolateral reticulospinal tract.[21,22,25,31,37] The fibers transmitting pain from the lower part of the trunk and lower extremities are located in the posterolateral part of the lateral spinothalamic tract, which is farther from the ventrolateral reticulospinal tract than from its anteromedial part.[3,12,15,44] For this reason, bilateral destruction of the pain fibers from the lower trunk and extremities at the upper cervical level seems to be safer than destruction of fibers from the upper trunk and upper extremities.[28,35] In the past decade, computerized tomography (CT)­guided percutaneous cordotomy has been used as an effective and safe method to destroy the lateral spinothalamic tract in patients with cancer pain.[17,18,20] Computerized tomography guidance offers the advantage of superior topographical orientation in the spinothalamic tract, which supplies selective ablation of the upper or lower segments of the body. To maximize the advantages, the technique described should be performed with the newly designed radiofrequency needle electrode system.[19] Computerized tomography­guided percutaneous bilateral selective cordotomy may prove to be the treatment of choice for patients suffering from bilateral cancer pain, because of the advantages of higher segmental selectivity and controlled ablation of neural structures at a higher cervical level under direct visualization. The present series included five patients with bilateral cancer pain in the lower trunk and extremities who were treated with CT-guided bilateral selective cordotomy. The bilateral selective cordotomy technique is described. CLINICAL MATERIAL AND METHODS Computerized tomography­guided cordotomy has been routinely used in our department since 1987. Between 1987 and 1996, 98 patients with intractable cancer pain were treated using CT-guided percutaneous cordotomy. Bilateral procedures were performed in five patients diagnosed with osteosarcoma, lumbar ependymoma, metastatic prostatic carcinoma, metastatic pulmonary carcinoma, and metastatic breast carcinoma, respectively. All patients had suffered from intractable bilateral pain of the lower extremities and lower trunk (Table 1). Only patients without pulmonary functional disorders were selected for bilateral cordotomy. A special needle electrode system was used for the CT-guided procedures (KCTE Kit; Radionics, Inc., Burlington, MA).[19] For this system, 20-22 gauge, thin-wall needles with plastic hubs were designed to avoid imaging artifacts. Measurements of the spinal cord diameter were made, and the portion of the active electrode that had been inserted was adjusted accordingly. We recently began using different electrode tip diameters for bilateral and unilateral cordotomies: we use 0.4-mm open-tip electrodes for unilateral procedures and 0.25-mm diameter and 2-mm open-tip electrodes for bilateral procedures. Placement of the needle at the C1­2 level can be seen in the lateral scanogram (Fig. 1). The needle is manipulated toward the anterior part of the spinal cord aided by axial CT sections, which facilitate topographical localization (Fig. 1). The target in percutaneous cordotomy is the lateral spinothalamic tract in the anterolateral part of the spinal cord at the C1­2 level, although the posterolateral part of the lateral spinothalamic tract should be targeted to control pain from the lower trunk and extremities, as is done in bilateral procedures.

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