Intraoperative herniation of an L5-S1 disc during microdiscectomy and transforaminal lumbar interbody fusion: a case report

INTRODUCTION: We report the progression of an intraoperative L5-S1 lumbar disc herniation that occurred during a routine microdiscectomy and transforaminal lumbar interbody fusion, which, to the best of our knowledge, has never been previously reported in the literature. The objective of this report is to bring to light the possibility of a lumbar disc herniating intraoperatively, and to demonstrate that accompanying neurologic involvement can be detected and subsequently addressed with the aid of neurophysiologic monitoring. CASE PRESENTATION: A 36-year-old African American woman, who had previously undergone minimally invasive microdiscectomy for a right L5-S1 herniated nucleus pulposus with full recovery, presented with a large reherniation of the L5-S1 disc on the right side. During her operation, while a tap was followed into the L5 left pedicle, there was a sudden profound spasm of our patient’s legs and back that lasted for the duration of 15 seconds, culminating in the loss of all somatosensory evoked potentials in our patient’s lower extremities. Exploration of this previous microlaminotomy site revealed a massive disc extrusion protruding through the microlaminotomy. Immediate removal of this extruded disc material restored all somatosensory evoked potentials and our patient awoke with no neurologic deficits. CONCLUSIONS: An intraoperative disc herniation in the lumbar spine, though very rare, can occur and can result in neurologic compromise as evidenced by the loss of somatosensory evoked potentials. By identifying the event, it can be remedied by evaluating the disc visually, removing extruded fragments and decompressing nerve roots with recovery of somatosensory evoked potentials and normal neurologic function postoperatively. If neurophysiological monitoring shows there is a sudden loss of response, then consideration should be given to the possibility of an acute intraoperative herniation.