The application of the technique for dorsal median sulcus mapping in intramedullary space occupying surgery: a single-center experience.

PURPOSE

To investigate the technique for dorsal median sulcus (DMS) mapping and assess its application value in preserving dorsal columnn (DC) function during intramedullary space occupying surgery based on a single-center experience.

METHODS

A retrospective analysis was conducted on 41 cases of intramedullary spinal cord tumor admitted to the Department of Neurosurgery at the First Affiliated Hospital of Xiamen University from March 2017 to August 2023. All included cases underwent intraoperative electrophysiological monitoring, and were divided into a study group (n = 18) and a control group (n = 23), based on whether DMS mapping technique was utilized. The general and clinical data, intraoperative electrophysiological monitoring data, and changes in patients' deep sensory function before and after surgery were collected. The postoperative neurological function protection of the two groups of patients with intramedullary spinal cord tumor was compared.

RESULTS

The present study introduces a technique for DMS mapping through the dorsal region stimulation. The amplitude and waveform of somatosensory evoked potentials (SEPs) recorded by the nerve stimulation probe consistently exhibited patterns relative to the dorsal column. This method demonstrated stable localization of the DMS during surgical procedures in all cases (18/18). Furthermore, compared to the double fork bipolar neurostimulator, the concentric bipolar neurostimulator induced SEPs with higher amplitudes in the dorsal column. There was no significant difference in tumor resection duration between the two groups, while postoperative hospitalization duration was shorter in the study group than in control group. During incision of dorsal column, SEP deterioration rate was 0/18 in study group and 4/23 in control group. During the procedure of tumor resection, the rate of deterioration in SEP was 5/18 in the study group and 9/23 in the control group. One week and three months post-surgery, the rate of decline in deep sensation in lower limbs was 4/18 and 3/18 respectively for the study group, while it was 8/23 and 9/23 for the control group.

CONCLUSION

The technique of DMS mapping is both stable and feasible, can assist the surgeon in accurately identifying the position of the posterior median sulci of the spinal cord and performing a precise dorsal columnotomy along the electrophysiological midline. This method holds great potential in enhancing the preservation of deep sensory function in patients' lower limbs post-surgery, thereby enabling them to benefit from the technique. Additionally, SEP Mapping of dorsal column aids in comprehending their function and facilitating rapid localization. Consequently, this approach introduces a novel neuroprotective measure for multimodal electrophysiological monitoring during intramedullary space occupying surgery.