Intraoperative neurophysiological mapping & localization of posterior median sulcus during intramedullary spinal cord tumor resection_technical communication

Abstract Objectives To assess orthodormic stimulation mapping technique for posterior median sulcus with some variation in parameters from that used in Simon study model. Methods A Case study of 51 years old female patient diagnosed with intramedullary lesion in the cervical segment, the patient was assigned for laminectomy, tumor exploration and biopsy. We used custom made bipolar stimulator for mapping; it allows variable flexible distance stimulation along the longitudinal axis of the posterior columns and recording from cortical somatosensory evoked potentials SSEPs C3-Fpz and C4-FPz and Cz-FPz channels. We used lateralization rather than phase reversal in localization of posterior median sulcus. Results We were able to identify the functional median sulcus with lateralization to contralateral side rather than phase reversal, the mapping was helpful method to identify PMS, which corresponded to the proposed radiological image's location. Conclusion Bipolar orthodormic stimulation can be done using lateralization rather than phase reversal technique. Using Higher Repetition Rate and intensity between 2 and 3 mA can decrease time needed to store averages without compromising evoking the potentials. Stimulation Intensity above 5 to 6 mA can stimulate motor tracts as well in cervical region.