Intraoperative Neuromonitoring Events in Transforaminal Endoscopy Using the Trans-Superior Articular Process Approach

Transforaminal endoscopic diskectomy is an effective approach for treatment of thoracic and lumbar disk pathologies. Classically, intraoperative neuromonitoring is used in these approaches given the risk to the exiting nerve root during transforaminal targeting. The trans-superior articular process (trans-SAP) approach is a targeting technique that docks on the ventrolateral SAP, allowing access to lateral recess pathology. This approach theoretically minimizes risk to the exiting nerve root which could occur with targeting or aberrant reaming. We investigate the safety of the trans-SAP approach by analyzing intraoperative neuromonitoring events in transforaminal endoscopic cases.

A retrospective analysis of 180 transforaminal endoscopic cases using the trans-SAP approach and free-running electromyography (EMG) neuromonitoring was performed. Cases were performed at 4 institutions; Houston Methodist Hospital, University Of Michigan, University of Washington, and Texas Back Institute, from 2021 to 2024. Neuromonitoring data using free-running EMG were carefully reviewed for each case and adverse monitoring events or EMG triggers were recorded.

Free-running EMG neuromonitoring was used in 180 of the 212 reviewed cases (84.91%). No adverse monitoring events or EMG triggers were recorded in 179 of the 180 monitored trans-SAP approach cases (99.44%). Three were performed awake with conscious sedation and no recorded events during targeting. One case was deemed safe without neuromonitoring based on thoracic foraminal pathology without cord compression. In the single case with a neuromonitoring event, multiple episodes of spontaneous neurotonic EMG activity were recorded during the dissection and diskectomy portion of the case, ultimately subsiding.

The trans-SAP approach for endoscopic diskectomy allows for safe access in transforaminal surgery. There was only one neuromonitoring event during the initial targeting in the 180 monitored or 3 awake trans-SAP cases included in this study that resolved without intraoperative or postoperative symptoms. These results could obviate the need for intraoperative neuromonitoring in these cases.