Surgical and clinical outcomes of ventral versus dorsal/lateral intradural extramedullary schwannomas: a retrospective comparative study.

Study design: Retrospective comparative study.

Objectives: To compare the surgical and clinical outcomes of ventral intradural extramedullary (IDEM) schwannomas to those of dorsal/lateral IDEM schwannomas.

Setting: The single institution in Japan.

Methods: This study included 94 patients with cervical or thoracic IDEM schwannomas who underwent tumor resection via a posterior approach between 2012 and 2022. Patients were categorized into Ventral (n = 12) and Dorsal/Lateral (n = 82) groups based on tumor localization. Demographic and surgical data, including surgical time and intraoperative motor evoked potential (MEP) changes, as well as clinical outcomes such as Japanese Orthopaedic Association (JOA) scores and gait function (modified McCormick scale, MMCS), were evaluated.

Results: The Ventral group had a significantly longer surgical time (p = 0.039) and was more likely to experience a temporary decrease in intraoperative MEP waveforms (p = 0.008) compared to the Dorsal/Lateral group. However, there were no significant differences between the groups in age at surgery, sex, level, tumor size, estimated blood loss, JOA score improvement, JOA recovery rate, or gait function at the final follow-up. Gross total resection (GTR) was achieved in all cases.

Conclusions: Despite longer surgical times and more likely to experience a temporary decrease in intraoperative MEP waveforms, ventral IDEM schwannomas do not result in significantly worse surgical or clinical outcomes compared to dorsal/lateral IDEM schwannomas. These findings suggest that even if the surgical procedure requires longer, gross total resection of ventral schwannomas via a posterior approach is resulting in favorable treatment outcomes.