Doral Root Entry Zone Lesioning

The spinal cord may be targeted for pain reduction by performing dorsal root entry zone lesioning (DREZ) and cordotomy. In a DREZ procedure, lesions are created in the superficial layers of the dorsal horn of the spinal cord called Rexed's laminae. Second-order afferent nociceptive fibers (A-beta) terminate here primarily lamina # 3, but can also be # 1, 2 (C-fibers). Patient selection is important since anatomically well-defined lesions respond best, and the procedure requires a general anesthetic for a multilevel laminectomy. DREZ lesioning is highly effective in treating chronic pain from brachial plexus avulsion injuries, postherpetic neuralgia, and malignancy pain from apancoasttumor. Spontaneous abnormal activity, hyperactivity, and corticospinal tract damage resulting in motor deficits may result from the procedure (Fig. 13.38).

Figure 13.38 T10 spinal cord cross section showing a radiofrequency dorsal root entry zone (RF-DREZ) lesion. Window shows organization of Rexed's lamina in the gray matter.

Cordotomy is sectioning of the spinothalamic tract located at the anterior-lateral portion of the spinal cord. It carries pain and temperature sensation from the periphery. Since the fibers cross over to the opposite side, or "decussate," two to five levels cephalad to their entry point into the cord, lesions of the tract cause loss of these senses two to five levels below it, on the opposite side (Figs. 13.39 and 13.40).

Brainstem mesencephalotomy is used to treat pain in the head, neck, and upper extremity by targeting the lateral spinothalamic tracts. At this level the spinothalamic tract affects the contralateral side as it has already decussated. Lesioning is performed in the periaqueductal gray

Figure 13.38 T10 spinal cord cross section showing a radiofrequency dorsal root entry zone (RF-DREZ) lesion. Window shows organization of Rexed's lamina in the gray matter.

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