Spinal cord DREZ lesioning has been used to successfully treat a number of neuropathic pain syndromes refractory to conventional treatment, including deafferentation syndromes, brachial and lumbar plexus avulsions, and pain secondary to spinal cord injury. In addition, nucleus caudalis DREZ lesioning has been successful in treating facial pain. Several clinical series demonstrate the utility of DREZ lesioning in the treatment of many intractable neuropathic pain syndromes and illustrate some of the limitations of the procedure.
Bernard reviewed the records of the first 18 patients with intractable facial pain treated with nucleus caudalis dorsal root entry zone lesions at Duke. The pain etiology varied, but the largest group was that of postherpetic neuralgia. In the immediate postoperative period, 90% of patients had satisfactory pain relief in comparison to 58% on subsequent follow-up. Seventy-one percent of those with postherpetic neuralgia had satisfactory relief on subsequent follow-up. Favorable results correlated with (1) a lesser preoperative sensory deficit, (2) pain restricted to trigeminal distributions, and (3) pain of a burning or lancinating/penetrating quality [Bernard, 1987].
Bullard and Nashold have reported their results in 25 patients undergoing nucleus caudalis DREZ lesions for refractory trigeminal neuralgia, atypical headaches or facial pain, multiple sclerosis, brainstem infarction, postherpetic neuralgia, posttraumatic closed head injuries, cancer-related pain [Rossitch, 1989] and postsurgical anesthesia dolorosa. Initial postsur-gery results were impressive for such usually refractory indications, with 24 of 25 patients having good to excellent pain relief at the time of discharge. Good to excellent results were maintained in 19 of 25 patients (76%) patients at 1 month and 17 of 25 patients (60%) at 3 months. Follow-up at 1 year included only 18 patients, but 12 of 18 (67%) maintained good to excellent pain relief, two reporting fair and four reporting poor pain relief. Because of disruption of the spinocerebellar pathway directly overlying the nucleus caudalis in the brainstem, 15 of 25 (60%) of patients had significant transient postoperative ataxia which resolved, in most, at 1 month. Minimal ataxia remained in three of 18 (17%) of patients at 1 year, although none of them considered it disabling. The other complications included transient diplopia in two patients and increased corneal anesthesia in 3. One general advantage of the nucleus caudalis DREZ lesion is that light touch is often preserved in the cornea so that keratitis is a very infrequent complication. Bullard and Nashold  reported one case of keratitis in their 25 patients. Their manuscript confirmed prior reports indicating that the nucleus caudalis DREZ offers significant benefit in managing very difficult pain in these patients.
At a meeting commemorating the 50th anniversary of Neurosurgery in Egypt, held in Cairo in March 1999, Drs. el-Naggar and Nashold discussed their results with alterations in the maximum temperature and anatomical extent of the nucleus caudalis DREZ lesions. Specifically, a lesion temperature of 80°C was used to obtain a more complete lesion of the nucleus results in a higher initial success rate and more durable pain relief. Previously, the eradication of perioral V2 and V3 pain required the rostral-most lesion be performed 10 to 12 mm above the obex. However, by increasing the lesion temperature from 75°C to 80°C, they have obtained satisfactory relief of perioral pain without lesioning above the obex. Further clinical studies are required before this fundamental change in lesioning parameters is widely recommended. However, their early results are promising.
In general, the nucleus caudalis DREZ operation has allowed for more robust management of varied pain syndromes, including those resulting from peripheral nervous system etiologies, than has the original spinal cord DREZ. Perhaps this is because of the difference in anatomical distribution of pain pathways relative to other sensory pathways. All the sensory relay nuclei are localized in 1- to 2-mm region of the posterior horn in the spinal cord, whereas they are spread through a much larger vertical nucleus extending from the level of C2 up through the medulla, with clear anatomical separation into surgically accessible zones in the trigeminal nuclei (the nucleus caudalis being the most caudal).
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