Spinal Column Shortening in Patients with Recurrent Tethered Cord Syndrome Leads to Improvements in Intraoperative Motor and Somatosensory Evoked Potentials

Introduction: Tethered cord syndrome can severely impact a patient’s quality of life due to back and leg pain, lower extremity weakness, and bowel and bladder dysfunction. Traditionally, these patients are offered detethering surgeries; however, there is a risk of persistent symptoms or re-tethering requiring further operations. Accordingly, a new surgical technique, posterior vertebral column subtraction osteotomy (PVCSO), was designed for recurrent cases to release the tension on the spinal cord by shortening the spinal column through a T12 vertebrectomy. Additional studies are needed to better capture the effectiveness of this surgical technique. In this study, we analyze the impact of PVCSO on intraoperative neurophysiological monitoring (IONM).

Methods: Patients undergoing a T12 PVCSO for recurrent tethered cord syndrome with pre- and post-magnetic resonance imaging (MRI) were identified at a single tertiary care hospital. Clinical data on pre-operative symptoms, surgical characteristics, and post-operative outcomes at 2- and 6-week follow-up were collected from patients’ medical records. IONM was captured throughout the operation and included somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs). SSEPs and MEPs were compared between baseline and immediately following shortening compression maneuvers with a change indicated by a 50-75% difference from the baseline.

Results: Six patients were identified undergoing PVCSO between the years 2019 and 2023. Patients had a median age at surgery of 36.5 years (range 27-50 years) and a median of 2.5 prior detethering surgeries (range 2-5). Lower extremity motor weakness, lower extremity sensory numbness, and bladder/bowel dysfunction were found in all patients preoperatively. IONM demonstrated improvements in MEPs and/or SSEPs in five out of six patients (83.3%). At six weeks follow up, patients experienced improvements in lower extremity strength (n=5, 83.3%), bladder/bowel control (n=4, 66.7%), and leg pain (n=4, 66.7%).

Conclusion : Improvements in MEPs and SSEPs can be seen intraoperatively following compression maneuvers during PVCSO, which correlates well to the early improvement in symptoms that patients commonly experience.