Correlation between neurogenic injury and lumbar disc degeneration in tethered cord syndrome: a retrospective MRI study based on somatosensory evoked potentials.

PURPOSE

This study examines the association between neurogenic injury and lumbar intervertebral disc degeneration (LDD) in tethered cord syndrome (TCS) by comparing lumbar sagittal parameters and disc degeneration between patients with normal and abnormal somatosensory evoked potential (SSEP) findings.

METHODS

We retrospectively analyzed clinical data from 43 patients diagnosed with TCS between July 2018 and July 2024. Based on tibial nerve somatosensory evoked potential (SSEP) examination results, patients were categorized into SSEP-normal and SSEP-abnormal groups. Demographic and clinical characteristics including height, weight, sex, age, BMI, smoking status, alcohol consumption, hypertension, and diabetes were recorded. Lumbar spine MRI T2-weighted images provided measurements of intervertebral disc degeneration grade, disc height, disc angle, lumbosacral angle, and lumbar lordosis angle. Statistical comparisons between groups employed chi-square tests, independent t-tests, Mann-Whitney U tests, and Fisher's exact tests. Spearman correlation analysis assessed relationships between SSEP abnormalities and degeneration grades across lumbar segments.

RESULTS

Of the 43 patients, 27 exhibited abnormal SSEP. The abnormal group demonstrated significantly higher LDD grades at L2-S1, with the strongest correlation at L5-S1 (P < 0.05). Overall and multi-segmental degeneration rates were elevated in this group. While lumbosacral and lumbar lordosis angles were larger in the abnormal group, these differences lacked statistical significance. The L5-S1 disc angle was significantly larger in the abnormal group (P < 0.05), whereas disc height did not differ between groups.

CONCLUSION

Patients with TCS and abnormal SSEP, reflecting more severe neurogenic injury, exhibited significantly more severe and widespread lumbar disc degeneration, particularly at caudal segments. These findings suggest that in TCS, the degree of neurogenic compromise may influence the severity of disc degeneration. Moreover, our results raise the possibility of a dynamic interaction between neural injury and spinal structural changes in the pathophysiology of TCS. This hypothesis warrants confirmation in larger, prospective studies using MRI and multimodal electrophysiology.