Neurophysiological monitoring for the nucleus caudalis dorsal root entry zone operation

OBJECTIVE: The purpose of this report is to describe a neurophysiological monitoring technique that can decrease the incidence of complications while maintaining the effectiveness of the nucleus caudalis dorsal root entry zone (DREZ) operation. METHODS: Needle electrodes were used to stimulate the supraorbital, infraorbital, mental, and median nerves after the nucleus caudalis was surgically exposed. The DREZ electrode was used to record responses from the various areas in and near the nucleus. The target site was localized. Before lesioning, the site was stimulated with the DREZ electrode and electromyographic activation was sought. If no activation was observed, a lesion was made. RESULTS: Five patients underwent a total of seven nucleus caudalis DREZ procedures with complete neurophysiological monitoring. The mean number of lesions per procedure in this series was 5.4. Six procedures (86%) resulted in immediate pain relief, and five (71%) produced persistent benefit after a mean follow-up period of 12 months. Only one patient (20%) (one of seven procedures) who underwent a unilateral DREZ procedure had ataxia, which resolved within a few days. No complications were noted at follow-up. CONCLUSION: Despite patients in this series receiving fewer lesions, the efficacy of the DREZ operation was comparable to that reported in earlier studies. There were fewer complications when neurophysiological monitoring was used. Such monitoring should be considered for nucleus caudalis DREZ operations.