The DREZ procedure: an update on technique.

The DREZ operation was first done in 1975 on a patient with arm pain following a brachial plexus avulsion. Since then approximately 500 patients have undergone the DREZ procedure under our care for treatment of various pain syndromes including deafferentation pain, post-herpetic neuralgia, and post-paraplegia pain. We report several modifications in instrumentation and technique. Currently, we use two types of electrodes for lesion production. The first is the standard 0.25 mm diameter, thermocouple, temperature monitoring electrode which has a 2 mm long tip for introduction into the spinal cord. A second type, recently modified from the original, is used only for lesioning the nucleus caudalis in patients with trigeminal post-herpetic neuralgia. Its tip is 3 mm long with insulation along the first 1 mm. This allows lesioning of the caudalis nucleus while sparing the more superficial spinocerebellar tracts. We no longer lesion only the dorsal root entry zones at each root level but include all the contiguous substantia gelatinosa between roots. With lesions only 1 mm apart this greatly increases the number of lesions and decreases the incidence of incomplete postoperative pain relief. In patients undergoing caudalis lesioning, we make two rows of lesions, one above the other, from C2 to slightly above the obex. This prevents sparing of the facial midline with resultant residual pain. Finally, lesions are made by heating the electrode tip to 75 degrees C for exactly 15 sec, thus allowing for a more uniform lesion. With these modifications, we have a decreased incidence of incomplete pain relief as well as a decreased incidence of complications, especially in patients undergoing caudalis lesioning.