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.

Two new right-angled electrodes have been designed for use at the dorsal root entry zone (DREZ) of the caudalis nucleus to provide relief of chronic facial pain. The electrode design was based on an anatomical study of the human caudalis nucleus at the cervicomedullary junction. Previously, caudalis nucleus DREZ operations were often followed by ipsilateral ataxia, usually in the arm. The new electrodes have significantly reduced this complication. A group of 21 patients with varied types of chronic facial pain have been treated, with pain relief in 70%.

New radiofrequency lesion dorsal root entry zone (DREZ) electrodes for relief of facial pain were designed based on a neuroanatomic study in man of the trigeminal nucleus caudalis at the cervicomedullary junction. The human brainstems of 3 normal postmortem specimens were sectioned with measurements and relationships of the trigeminal nucleus caudalis, segmental tracts, spinocerebellar tracts and dorsal columns. Two right-angle DREZ electrodes were made by Radionics for producing DREZ lesions in the trigeminal nucleus caudalis to treat deafferentation facial pain.

About 10% of paraplegics suffer from intractable pain. The onset of pain may be immediate or delayed for months to several years after the injury. The delayed onset of pain is highly suggestive of the development of a spinal cyst. This is a report of 18 paraplegics who developed a delayed onset of intractable pain who were found at the time of surgery to have associated spinal cord cysts. Treatment consisted of the dorsal root entry zone (DREZ) operation in addition to evacuation of the cyst. Burning pain was the most common complaint occurring years after the trauma. In this study we compared the relationship between the onset and character of the pain, the time of the spinal injury, the operative findings, and the results of the DREZ procedure and evacuation of the traumatic spinal cyst. We believe that the combination of paraplegia, pain and spinal cyst has not been emphasized in the neurosurgical literature although it is well known that cystic formation can follow spinal trauma. Two patients developed spinal cysts with nontraumatic lesions of the spinal cord. A single cyst was found in 14 patients while four had two separate cysts. The diagnosis was made on the basis of history and clinical examination with radiographic confirmation using delayed CT scan and myelography and more recently magnetic resonance imaging. Intraoperative ultrasound was employed in the study of some patients. All patients were treated with combined DREZ lesions and evacuation of the cysts with good pain relief in 77.7%.