Surgery for intramedullary spinal cord ependymomas in the neuromonitoring era: results from a consecutive series of 100 patients

Objective: The established treatment of intramedullary spinal cord ependymomas (ISCEs) is resection. Surgical series reporting treatment results often lack homogeneity, as these are collected over long time spans and their analysis is plagued by surgical learning curves and inconsistent use of intraoperative neurophysiological monitoring (IONM). The authors report the oncological and functional long-term outcomes in a modern series of 100 consecutive ISCEs that were resected between 2000 and 2015 by a surgically experienced team that consistently utilized IONM. Methods: In this retrospective study, the authors tailored surgical strategy and multimodal IONM, including somatosensory evoked potentials, muscle motor evoked potentials (mMEPs), and D-waves, with the aim of gross-total resection (GTR). Preservation of the D-wave was the primary objective, and preservation of mMEPs was the second functional objective. Functional status was evaluated using the modified McCormick Scale (MMS) preoperatively, postoperatively, and at follow-up. Results: Preoperatively, 89 patients were functionally independent (MMS grade I or II). A GTR was achieved in 89 patients, 10 patients had a stable residual, and 1 patient underwent reoperation for tumor progression. At a mean follow-up of 65.4 months, 82 patients were functionally independent, and 11 lost their functional independence after surgery (MMS grades III-V). Muscle MEP loss predicted short-term postoperative worsening (p < 0.0001) only, while the strongest predictors of a good functional long-term outcome were lower preoperative MMS grades (p < 0.0001) and D-wave preservation. D-wave monitorability was 67%; it was higher with lower preoperative MMS grades and predicted a better recovery (p = 0.01). Conclusions: In this large series of ISCEs, a high rate of GTR and long-term favorable functional outcome were achieved. Short- and long-term functional outcomes were best reflected by mMEPs and D-wave monitoring, respectively.